| 1. |
- Zhang, Lixiu, et al.
(författare)
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Advances in the Application of Perovskite Materials
- 2023
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Ingår i: NANO-MICRO LETTERS. - : SHANGHAI JIAO TONG UNIV PRESS. - 2311-6706. ; 15:1
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Forskningsöversikt (refereegranskat)abstract
- Nowadays, the soar of photovoltaic performance of perovskite solar cells has set off a fever in the study of metal halide perovskite materials. The excellent optoelectronic properties and defect tolerance feature allow metal halide perovskite to be employed in a wide variety of applications. This article provides a holistic review over the current progress and future prospects of metal halide perovskite materials in representative promising applications, including traditional optoelectronic devices (solar cells, light-emitting diodes, photodetectors, lasers), and cutting-edge technologies in terms of neuromorphic devices (artificial synapses and memristors) and pressure-induced emission. This review highlights the fundamentals, the current progress and the remaining challenges for each application, aiming to provide a comprehensive overview of the development status and a navigation of future research for metal halide perovskite materials and devices.
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| 2. |
- Qing, Jian, et al.
(författare)
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Aligned and Graded Type-II Ruddlesden-Popper Perovskite Films for Efficient Solar Cells
- 2018
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Ingår i: Advanced Energy Materials. - : WILEY-V C H VERLAG GMBH. - 1614-6832 .- 1614-6840. ; 8:21
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Tidskriftsartikel (refereegranskat)abstract
- Recently, Ruddlesden-Popper perovskites (RPPs) have attracted increasing interests due to their promising stability. However, the efficiency of solar cells based on RPPs is much lower than that based on 3D perovskites, mainly attributed to their poor charge transport. Herein, a simple yet universal method for controlling the quality of RPP films by a synergistic effect of two additives in the precursor solution is presented. RPP films achieved by this method show (a) high quality with uniform morphology, enhanced crystallinity, and reduced density of sub-bandgap states, (b) vertically oriented perovskite frameworks that facilitate efficient charge transport, and (c) type-II band alignment that favors self-driven charge separation. Consequently, a hysteresis-free RPP solar cell with a power conversion efficiency exceeding 12%, which is much higher than that of the control device (1.5%), is achieved. The findings will spur new developments in the fabrication of high-quality, aligned, and graded RPP films essential for realizing efficient and stable perovskite solar cells.
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| 3. |
- Wang, Heyong, et al.
(författare)
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Efficient perovskite light-emitting diodes based on a solution-processed tin dioxide electron transport layer
- 2018
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Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 6:26, s. 6996-7002
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Tidskriftsartikel (refereegranskat)abstract
- To achieve high-performance perovskite light-emitting diodes (PeLEDs), an appropriate functional layer beneath the perovskite emissive layer is significantly important to modulate the morphology of the perovskite film and to facilitate charge injection and transport in the device. Herein, for the first time, we report efficient n-i-p structured PeLEDs using solution-processed SnO2 as an electron transport layer. Three-dimensional perovskites, such as CH(NH2)(2)PbI3 and CH3NH3PbI3, are found to be more chemically compatible with SnO2 than with commonly used ZnO. In addition, SnO2 shows good transparency, excellent morphology and suitable energy levels. These properties make SnO2 a promising candidate in both three-and low-dimensional PeLEDs, among which a high external quantum efficiency of 7.9% has been realized. Furthermore, interfacial materials that are widely used to improve the device performances of ZnO-based PeLEDs are also applied on SnO2-based PeLEDs and their effects have been systematically studied. In contrast to ZnO, SnO2 modified by these interfacial materials shows detrimental effects due to photoluminescence quenching.
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| 4. |
- Wang, Heyong, et al.
(författare)
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Perovskite-molecule composite thin films for efficient and stable light-emitting diodes
- 2020
-
Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Although perovskite light-emitting diodes (PeLEDs) have recently experienced significant progress, there are only scattered reports of PeLEDs with both high efficiency and long operational stability, calling for additional strategies to address this challenge. Here, we develop perovskite-molecule composite thin films for efficient and stable PeLEDs. The perovskite-molecule composite thin films consist of in-situ formed high-quality perovskite nanocrystals embedded in the electron-transport molecular matrix, which controls nucleation process of perovskites, leading to PeLEDs with a peak external quantum efficiency of 17.3% and half-lifetime of approximately 100 h. In addition, we find that the device degradation mechanism at high driving voltages is different from that at low driving voltages. This work provides an effective strategy and deep understanding for achieving efficient and stable PeLEDs from both material and device perspectives.
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| 5. |
- Ao, Hong, et al.
(författare)
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Orbital climate variability on the northeastern Tibetan Plateau across the Eocene-Oligocene transition
- 2020
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- The first major build-up of Antarctic glaciation occurred in two consecutive stages across the Eocene-Oligocene transition (EOT): the EOT-1 cooling event at similar to 34.1-33.9Ma and the Oi-1 glaciation event at similar to 33.8-33.6Ma. Detailed orbital-scale terrestrial environmental responses to these events remain poorly known. Here we present magnetic and geochemical climate records from the northeastern Tibetan Plateau margin that are dated precisely from similar to 35.5 to 31Ma by combined magneto- and astro-chronology. These records suggest a hydroclimate transition at similar to 33.7Ma from eccentricity dominated cycles to oscillations paced by a combination of eccentricity, obliquity, and precession, and confirm that major Asian aridification and cooling occurred at Oi-1. We conclude that this terrestrial orbital response transition coincided with a similar transition in the marine benthic delta O-18 record for global ice volume and deep-sea temperature variations. The dramatic reorganization of the Asian climate system coincident with Oi-1 was, thus, a response to coeval atmospheric CO2 decline and continental-scale Antarctic glaciation. Marine records indicate a greenhouse to icehouse climate transition at similar to 34 million years ago, but how the climate changed within continental interiors at this time is less well known. Here, the authors show an orbital climate response shift with aridification on the northeastern Tibetan Plateau during this time.
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| 6. |
- Chen, Mengyun, et al.
(författare)
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Kinetically Controlled Synthesis of Quasi-Square CsPbI3 Nanoplatelets with Excellent Stability
- 2023
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Ingår i: Small. - : WILEY-V C H VERLAG GMBH. - 1613-6810 .- 1613-6829.
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Tidskriftsartikel (refereegranskat)abstract
- Nanoplatelets (NPLs) share excellent luminescent properties with their symmetric quantum dots counterparts and entail special characters benefiting from the shape, like the thickness-dependent bandgap and anisotropic luminescence. However, perovskite NPLs, especially those based on iodide, suffer from poor spectral and phase stability. Here, stable CsPbI3 NPLs obtained by accelerating the crystallization process in ambient-condition synthesis are reported. By this kinetic control, the rectangular NPLs into quasi-square NPLs are tuned, where enlarged width endows the NPLs with a lower surface-area-to-volume ratio (S/V ratio), leading to lower surficial energy and thus improved endurance against NPL fusion (cause for spectral shift or phase transformation). The accelerated crystallization, denoting the fast nucleation and short period of growth in this report, is enabled by preparing a precursor with complete transformation of PbI2 into intermediates (PbI3-), through an additional iodide supplier (e.g., zinc iodide). The excellent color stability of the materials remains in the light-emitting diodes under various bias stresses.
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| 7. |
- Chen, Zhan, et al.
(författare)
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Photoluminescence Enhancement for Efficient Mixed-Halide Blue Perovskite Light-Emitting Diodes
- 2023
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Ingår i: Advanced Optical Materials. - : WILEY-V C H VERLAG GMBH. - 2162-7568 .- 2195-1071. ; 11:6
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Tidskriftsartikel (refereegranskat)abstract
- The development of highly efficient blue perovskite light-emitting diodes (PeLEDs) remains a big challenge, requiring more fundamental investigations. In this work, significant photoluminescence enhancement in mixed halide blue perovskite films is demonstrated by using a molecule, benzylphosphonic acid, which eventually doubles the external quantum efficiency to 6.3% in sky-blue PeLEDs. The photoluminescence enhancement is achieved by forming an oxide-bonded perovskite surface at grain boundaries and suppressing electron-phonon interaction, which enhances the radiative recombination rate and reduces the nonradiative recombination rate, respectively. Moreover, severe thermal quenching is observed in the blue perovskite films, which can be explained by a two-step mechanism involving exciton dissociation and electron-phonon interaction. The results suggest that enhancing the radiative recombination rate and reducing the electron-phonon interaction-induced nonradiative recombination rate are crucial for achieving blue perovskite films with strong emission at or above room temperature.
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| 8. |
- Qian, Deping, et al.
(författare)
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Design rules for minimizing voltage losses in high-efficiency organic solar cells
- 2018
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Ingår i: Nature Materials. - : NATURE PUBLISHING GROUP. - 1476-1122 .- 1476-4660. ; 17:8, s. 703-
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Tidskriftsartikel (refereegranskat)abstract
- The open-circuit voltage of organic solar cells is usually lower than the values achieved in inorganic or perovskite photovoltaic devices with comparable bandgaps. Energy losses during charge separation at the donor-acceptor interface and non-radiative recombination are among the main causes of such voltage losses. Here we combine spectroscopic and quantum-chemistry approaches to identify key rules for minimizing voltage losses: (1) a low energy offset between donor and acceptor molecular states and (2) high photoluminescence yield of the low-gap material in the blend. Following these rules, we present a range of existing and new donor-acceptor systems that combine efficient photocurrent generation with electroluminescence yield up to 0.03%, leading to non-radiative voltage losses as small as 0.21 V. This study provides a rationale to explain and further improve the performance of recently demonstrated high-open-circuit-voltage organic solar cells.
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| 9. |
- Shi, Xiaobo, et al.
(författare)
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Optical Energy Losses in Organic-Inorganic Hybrid Perovskite Light-Emitting Diodes
- 2018
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Ingår i: Advanced Optical Materials. - : John Wiley & Sons. - 2162-7568 .- 2195-1071. ; 6:17
-
Tidskriftsartikel (refereegranskat)abstract
- Light-emitting diodes (LEDs) based on organic-inorganic hybrid perovskites, in particular, 3D and quasi-2D ones, are in the fast development and their external quantum efficiencies (EQEs) have exceeded 10%, making them competitive candidates toward large-area and low-cost light-emitting applications allowing printing techniques. Similar to other LED categories, light out-coupling efficiency is an important parameter determining the EQE of perovskite LEDs (PeLEDs), which, however, is scarcely studied, limiting further efficiency improvement and understanding of PeLEDs. In this work, for the first time, optical energy losses in PeLEDs are investigated through systematic optical simulations, which reveal that the 3D and quasi-2D PeLEDs can achieve theoretically maximum EQEs of approximate to 25% and approximate to 20%, respectively, in spite of their high refractive indices. These results are consistent with the reported experimental data. This work presents primary understanding of the optical energy losses in PeLEDs and will spur new developments in the aspects of device engineering and light extraction techniques to boost the EQEs of PeLEDs.
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| 10. |
- Wang, Heyong, et al.
(författare)
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Dynamic Redistribution of Mobile Ions in Perovskite Light-Emitting Diodes
- 2021
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Ingår i: Advanced Functional Materials. - : WILEY-V C H VERLAG GMBH. - 1616-301X .- 1616-3028. ; 31:8
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Tidskriftsartikel (refereegranskat)abstract
- Despite quick development of perovskite light-emitting diodes (PeLEDs) during the past few years, the fundamental mechanisms on how ion migration affects device efficiency and stability remain unclear. Here, it is demonstrated that the dynamic redistribution of mobile ions in the emissive layer plays a key role in the performance of PeLEDs and can explain a range of abnormal behaviours commonly observed during the device measurement. The dynamic redistribution of mobile ions changes charge-carrier injection and leads to increased recombination current; at the same time, the ion redistribution also changes charge transport and results in decreased shunt resistance current. As a result, the PeLEDs show hysteresis in external quantum efficiencies (EQEs) and radiance, that is, higher EQEs and radiance during the reverse voltage scan than during the forward scan. In addition, the changes on charge injection and transport induced by the ion redistribution also well explain the rise of the EQE/radiance values under constant driving voltages. The argument is further rationalized by adding extra formamidinium iodide (FAI) into optimized PeLEDs based on FAPbI(3), resulting in more significant hysteresis and shorter operational stability of the PeLEDs.
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| 11. |
- Yi, Chang, et al.
(författare)
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Intermediate-phase-assisted low-temperature formation of gamma-CsPbI3 films for high-efficiency deep-red light-emitting devices
- 2020
-
Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- Black phase CsPbI3 is attractive for optoelectronic devices, while usually it has a high formation energy and requires an annealing temperature of above 300 degrees C. The formation energy can be significantly reduced by adding HI in the precursor. However, the resulting films are not suitable for light-emitting applications due to the high trap densities and low photoluminescence quantum efficiencies, and the low temperature formation mechanism is not well understood yet. Here, we demonstrate a general approach for deposition of gamma -CsPbI3 films at 100 degrees C with high photoluminescence quantum efficiencies by adding organic ammonium cations, and the resulting light-emitting diode exhibits an external quantum efficiency of 10.4% with suppressed efficiency roll-off. We reveal that the low-temperature crystallization process is due to the formation of low-dimensional intermediate states, and followed by interionic exchange. This work provides perspectives to tune phase transition pathway at low temperature for CsPbI3 device applications. Exploiting low-temperature formed black phase CsPbI3 for light-emitting applications remains a challenge. Here, the authors propose a method to enable the deposition of gamma -CsPbI3 films at 100C and demonstrate a light-emitting diode with an external quantum efficiency of 10.4% with suppressed efficiency roll-off.
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| 12. |
- Zhang, Yuehui, et al.
(författare)
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Hyperandrogenism and insulin resistance modulate gravid uterine and placental ferroptosis in PCOS-like rats. : Uterine and placental ferroptosis in pregnant PCOS-like rats
- 2020
-
Ingår i: The Journal of endocrinology. - 1479-6805. ; 246:3, s. 247-63
-
Tidskriftsartikel (refereegranskat)abstract
- Previous studies in rats showed that maternal exposure to 5α-dihydrotestosterone (DHT) and insulin (INS) from gestational day 7.5 to 13.5 induces hyperandrogenism and insulin resistance (HAIR) and subsequently leads to placental insufficiency and fetal loss. We therefore hypothesized that maternal HAIR triggers ferroptosis in the uterus and placenta in association with fetal loss in pregnant rats. Compared with controls, we found that co-exposure to DHT and INS led to decreased levels of Gpx4 and glutathione (GSH), increased GSH+glutathione disulfide (GSSG) and malondialdehyde (MDA), aberrant expression of ferroptosis-associated genes (Acsl4, Tfrc, Slc7a11, and Gclc), increased iron deposition, and activated ERK/p38/JNK phosphorylation in the gravid uterus. However, in the placenta, DHT and INS exposure only partially altered the expression of ferroptosis-related markers (e.g., Gpx4, GSH+GSSG, MDA, Gls2 and Slc7a11 mRNAs, and phosphorylated p38 levels). In the uteri co-exposed to DHT and INS, we also observed shrunken mitochondria with electron-dense cristae, and increased Dpp4 mRNA expression. In contrast, in placentas co-exposed to DHT and INS we found decreased Dpp4 mRNA expression and increased Cisd1 mRNA expression. Further, DHT+INS-exposed pregnant rats exhibited decreased apoptosis in the uterus and increased necroptosis in the placenta. Our findings suggest that maternal HAIR causes the activation of ferroptosis in the gravid uterus and placenta, although this is mediated via different mechanisms operating at the molecular and cellular levels. Furthermore, our data suggest other cell death pathways may play a role in coordinating or compensating for HAIR-induced ferroptosis when the gravid uterus and placenta are dysfunctional.
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| 13. |
- Zhang, Yuehui, et al.
(författare)
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Hyperandrogenism and insulin resistance modulate gravid uterine and placental ferroptosis in PCOS-like rats.
- 2020
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Ingår i: Journal of Endocrinology. - : Bioscientifica. - 0022-0795 .- 1479-6805. ; 246:3, s. 247-263
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies in rats showed that maternal exposure to 5α-dihydrotestosterone (DHT) and insulin (INS) from gestational day 7.5 to 13.5 induces hyperandrogenism and insulin resistance (HAIR) and subsequently leads to placental insufficiency and fetal loss. We therefore hypothesized that maternal HAIR triggers ferroptosis in the uterus and placenta in association with fetal loss in pregnant rats. Compared with controls, we found that co-exposure to DHT and INS led to decreased levels of Gpx4 and glutathione (GSH), increased GSH+glutathione disulfide (GSSG) and malondialdehyde (MDA), aberrant expression of ferroptosis-associated genes (Acsl4, Tfrc, Slc7a11, and Gclc), increased iron deposition, and activated ERK/p38/JNK phosphorylation in the gravid uterus. However, in the placenta, DHT and INS exposure only partially altered the expression of ferroptosis-related markers (e.g., Gpx4, GSH+GSSG, MDA, Gls2 and Slc7a11 mRNAs, and phosphorylated p38 levels). In the uteri co-exposed to DHT and INS, we also observed shrunken mitochondria with electron-dense cristae, and increased Dpp4 mRNA expression. In contrast, in placentas co-exposed to DHT and INS we found decreased Dpp4 mRNA expression and increased Cisd1 mRNA expression. Further, DHT+INS-exposed pregnant rats exhibited decreased apoptosis in the uterus and increased necroptosis in the placenta. Our findings suggest that maternal HAIR causes the activation of ferroptosis in the gravid uterus and placenta, although this is mediated via different mechanisms operating at the molecular and cellular levels. Furthermore, our data suggest other cell death pathways may play a role in coordinating or compensating for HAIR-induced ferroptosis when the gravid uterus and placenta are dysfunctional.
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| 14. |
- Almquist, Ben, et al.
(författare)
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Outstanding Reviewers for Materials Horizons in 2019
- 2020
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Ingår i: Materials Horizons. - : ROYAL SOC CHEMISTRY. - 2051-6347 .- 2051-6355. ; 7:5, s. 1207-1207
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We would like to take this opportunity to highlight the Outstanding Reviewers for Materials Horizons in 2019, as selected by the editorial team for their significant contribution to the journal.
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| 15. |
- Chen, Mengying, et al.
(författare)
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Neonatal repetitive pain in rats leads to impaired spatial learning and dysregulated hypothalamic-pituitary-adrenal axis function in later life
- 2016
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- Preterm birth is a major health issue. As part of their life-saving care, most preterm infants require hospitalization and are inevitably exposed to repetitive skin-breaking procedures. The long-term effects of neonatal repetitive pain on cognitive and emotional behaviors involving hypothalamic-pituitary-adrenal (HPA) axis function in young and adult rats are unknown. From P8 to P85, mechanical hypersensitivity of the bilateral hindpaws was observed in the Needle group (P < 0.001). Compared with the Tactile group, the Needle group took longer to find the platform on P30 than on P29 (P = 0.03), with a decreased number of original platform site crossings during the probe trial of the Morris water maze test (P = 0.026). Moreover, the Needle group spent more time and took longer distances in the central area than the Tactile group in the Open-field test, both in prepubertal and adult rats (P < 0.05). The HPA axis function in the Needle group differed from the Tactile group (P < 0.05), with decreased stress responsiveness in prepuberty and puberty (P < 0.05) and increased stress responsiveness in adulthood (P < 0.05). This study indicates that repetitive pain that occurs during a critical period may cause severe consequences, with behavioral and neuroendocrine disturbances developing through prepuberty to adult life.
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| 16. |
- Cheng, Li-Peng, et al.
(författare)
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Efficient CsPbBr3 Perovskite Light-Emitting Diodes Enabled by Synergetic Morphology Control
- 2019
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Ingår i: Advanced Optical Materials. - : WILEY-V C H VERLAG GMBH. - 2162-7568 .- 2195-1071. ; 7:4
-
Tidskriftsartikel (refereegranskat)abstract
- The development of solution-processed inorganic metal halide perovskite light-emitting diodes (PeLEDs) is currently hindered by low emission efficiency due to morphological defects and severe non-radiative recombination in all-inorganic perovskite emitters. Herein, bright PeLEDs are demonstrated by synergetic morphology control over cesium lead bromide (CsPbBr3) perovskite films with the combination of two additives. The phenethylammonium bromide additive enables the formation of mixed-dimensional CsPbBr3 perovskites featuring the reduced grain size (amp;lt;15 nm) and efficient energy funneling, while the dielectric polyethyleneglycol additive promotes the formation of highly compact and pinhole-free perovskite films with defect passivation at grain boundaries. Consequently, green PeLEDs achieve a current efficiency of 37.14 cd A(-1) and an external quantum efficiency of 13.14% with the maximum brightness up to 45 990 cd m(-2) and high color purity. Furthermore, this method can be effectively extended to realize flexible PeLEDs on plastic substrates with a high efficiency of 31.0 cd A(-1).
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| 17. |
- Hu, Min, et al.
(författare)
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Hyperandrogenism and insulin resistance induce gravid uterine defects in association with mitochondrial dysfunction and aberrant ROS production.
- 2019
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Ingår i: American journal of physiology. Endocrinology and metabolism. - : American Physiological Society. - 1522-1555 .- 0193-1849. ; 316:5
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Tidskriftsartikel (refereegranskat)abstract
- Women with polycystic ovary syndrome (PCOS) are at increased risk of miscarriage, which often accompanies the hyperandrogenism and insulin resistance seen in these patients. However, neither the combinatorial interaction between these two PCOS-related etiological factors nor the mechanisms of their actions in the uterus during pregnancy are well understood. We hypothesised that hyperandrogensim and insulin resistance exert a causative role in miscarriage by inducing defects in uterine function that are accompanied by mitochondrial-mediated oxidative stress, inflammation and perturbed gene expression. Here we tested this hypothesis by studying the metabolic, endocrine and uterine abnormalities in pregnant rats after exposure to daily injection of 5α-dihydrotestosterone (DHT, 1.66 mg/kg body weight/day) and/or insulin (6.0 IU/day) from gestational day 7.5 to 13.5. We showed that while DHT-exposed and insulin-exposed pregnant rats presented impaired insulin sensitivity, DHT+insulin-exposed pregnant rats exhibited hyperandrogenism and peripheral insulin resistance, which mirrors pregnant PCOS patients. Compared to controls, hyperandrogenism and insulin resistance in the dam was associated with alterations in uterine morphology and aberrant expression of genes responsible for decidualization, placentation, angiogenesis and insulin signaling. Moreover, we observed changes in uterine mitochondrial function and homeostasis and suppression of both oxidative and antioxidative defenses in response to the hyperandrogenism and insulin resistance. These findings demonstrate that hyperandrogenism and insulin resistance induce mitochondria-mediated damage and a resulting imbalance between oxidative and antioxidative stress responses in the gravid uterus.
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| 18. |
- Hu, Min, et al.
(författare)
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Perturbed ovarian and uterine glucocorticoid receptor signaling accompanies the balanced regulation of mitochondrial function and NFκB-mediated inflammation under conditions of hyperandrogenism and insulin resistance.
- 2019
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Ingår i: Life sciences. - : Elsevier BV. - 1879-0631 .- 0024-3205. ; 232
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to determine whether glucocorticoid receptor (GR) signaling, mitochondrial function, and local inflammation in the ovary and uterus are intrinsically different in rats with hyperandrogenism and insulin resistance compared to controls.Female Sprague Dawley rats were exposed to daily injections of human chorionic gonadotropin and/or insulin.In both the ovary and the uterus, decreased expression of the two GR isoforms was concurrent with increased expression of Fkbp51 but not Fkbp52 mRNA in hCG+insulin-treated rats. However, these rats exhibited contrasting regulation of Hsd11b1 and Hsd11b2 mRNAs in the two tissues. Further, the expression of several oxidative phosphorylation-related proteins decreased in the ovary and uterus following hCG and insulin stimulation, in contrast to increased expression of many genes involved in mitochondrial function and homeostasis. Additionally, hCG+insulin-treated rats showed increased expression of ovarian and uterine NFκB signaling proteins and Tnfaip3 mRNA. The mRNA expression of Il1b, Il6, and Mmp2 was decreased in both tissues, while the mRNA expression of Tnfa, Ccl2, Ccl5, and Mmp3 was increased in the uterus. Ovaries and uteri from animals co-treated with hCG and insulin showed increased collagen deposition compared to controls.Our observations suggest that hyperandrogenism and insulin resistance disrupt ovarian and uterine GR activation and trigger compensatory or adaptive effects for mitochondrial homeostasis, allowing tissue-level maintenance of mitochondrial function in order to limit ovarian and uterine dysfunction. Our study also suggests that hyperandrogenism and insulin resistance activate NFκB signaling resulting in aberrant regulation of inflammation-related gene expression.
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| 19. |
- Kumawat, Naresh Kumar, et al.
(författare)
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Blue perovskite light-emitting diodes: progress, challenges and future directions
- 2019
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Ingår i: Nanoscale. - : ROYAL SOC CHEMISTRY. - 2040-3364 .- 2040-3372. ; 11:5, s. 2109-2120
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Forskningsöversikt (refereegranskat)abstract
- Metal halide perovskites have excellent optical and electrical properties and can be easily processed via low-cost solution-based techniques like blade-coating and inkjet printing, promising a bright future for various optoelectronic applications. Recently, encouraging progress has been made in perovskite light-emitting diodes (PeLEDs). Green, red, and near-infrared PeLEDs have achieved high external quantum efficiencies of more than 20%. However, as historically blue electroluminescence remains challenging in all previous LED technologies, we are witnessing a similar case with the development of blue PeLEDs, an essential part of displays and solid-state lighting, which lag far behind those of their counterparts. Herein, we review the recent progress of blue PeLEDs and discuss the main challenges including colour instability, poor photoluminescence efficiency and emission quenching by interlayers. Future directions are provided to facilitate the development of efficient blue PeLEDs.
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| 20. |
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| 21. |
- Liu, Xiaoke, et al.
(författare)
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Metal halide perovskites for light-emitting diodes
- 2021
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Ingår i: Nature Materials. - : NATURE PUBLISHING GROUP. - 1476-1122 .- 1476-4660. ; 20:1, s. 10-21
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Forskningsöversikt (refereegranskat)abstract
- The development of perovskite emitters, their use in light-emitting devices, and the challenges in enhancing the efficiency and stability, as well as reducing the potential toxicity of this technology are discussed in this Review. Metal halide perovskites have shown promising optoelectronic properties suitable for light-emitting applications. The development of perovskite light-emitting diodes (PeLEDs) has progressed rapidly over the past several years, reaching high external quantum efficiencies of over 20%. In this Review, we focus on the key requirements for high-performance PeLEDs, highlight recent advances on materials and devices, and emphasize the importance of reliable characterization of PeLEDs. We discuss possible approaches to improve the performance of blue and red PeLEDs, increase the long-term operational stability and reduce toxicity hazards. We also provide an overview of the application space made possible by recent developments in high-efficiency PeLEDs.
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| 22. |
- Liu, Xiaoke, et al.
(författare)
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Organic-Inorganic Hybrid Ruddlesden-Popper Perovskites: An Emerging Paradigm for High-Performance Light-Emitting Diodes
- 2018
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Ingår i: The Journal of Physical Chemistry Letters. - : AMER CHEMICAL SOC. - 1948-7185. ; 9:9, s. 2251-2258
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Tidskriftsartikel (refereegranskat)abstract
- Recently, lead halide perovskite materials have attracted extensive interest, in particular, in the research field of solar cells. These materials are fascinating "soft" materials with semiconducting properties comparable to the best inorganic semiconductors like silicon and gallium arsenide. As one of the most promising perovskite family members, organic-inorganic hybrid Ruddlesden-Popper perovskites (HRPPs) offer rich chemical and structural flexibility for exploring excellent properties for optoelectronic devices, such as solar cells and light-emitting diodes (LEDs). In this Perspective, we present an overview of HRPPs on their structural characteristics, synthesis of pure HRPP compounds and thin films, control of their preferential orientations, and investigations of heterogeneous HRPP thin films. Based on these recent advances, future directions and prospects have been proposed. HRPPs are promising to open up a new paradigm for high-performance LEDs.
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| 23. |
- Ponseca, Carlito, et al.
(författare)
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Pulsed Terahertz Emission from Solution-Processed Lead Iodide Perovskite Films
- 2019
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Ingår i: ACS Photonics. - : AMER CHEMICAL SOC. - 2330-4022. ; 6:5, s. 1175-1181
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Tidskriftsartikel (refereegranskat)abstract
- We report pulsed terahertz (THz) emission from solution-processed metal halide perovskite films with electric field 1 order of magnitude lower than p-InAs, an efficient THz emitter. Such emission is enabled by a unique combination of efficient charge separation, high carrier mobilities, and more importantly surface defects. The mechanism of generation was identified by investigating the dependence of the THz electric field amplitude on surface defect densities, excess charge carriers, excitation intensity and energy, temperature, and external electric field. We also show for the first time THz emission from a curved surface, which is not possible for any crystalline semiconductor and paves the way to focus high-intensity sources. These results represent a possible new direction for perovskite optoelectronics and for THz emission spectroscopy as a complementary tool in investigating surface defects on metal halide perovskites, of fundamental importance in the optimization of solar cells and light-emitting diodes.
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| 24. |
- Qin, Jiajun, et al.
(författare)
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Carrier Dynamics and Evaluation of Lasing Actions in Halide Perovskites
- 2021
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Ingår i: TRENDS IN CHEMISTRY. - : ELSEVIER. - 2589-5974. ; 3:1, s. 34-46
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Forskningsöversikt (refereegranskat)abstract
- Metal halide perovskites have shown rapid development in various fields such as photovoltaics, photodetectors, light-emitting diodes (LEDs), and optically pumped lasers owing to their superior optoelectronic properties. Here, we review the basic optoelectronic properties of halide perovskites from a photophysical perspective. We highlight that halide perovskites are promising in various optoelectronic devices functioning at a wide range of carrier densities. We discuss optically and electrically generated carrier density under two different excitation modes [continuous wave (CW) and pulsed] as well as the impact of carrier density on the optoelectronic behavior of perovskites. Moreover, we discuss lasing actions at high carrier densities and summarize key rules to evaluate the lasing actions. Last, we provide an outlook on perovskite-based electrically pumped lasers.
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| 25. |
- Qing, Jian, et al.
(författare)
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High-Quality Ruddlesden-Popper Perovskite Films Based on In Situ Formed Organic Spacer Cations
- 2019
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 31:41
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Tidskriftsartikel (refereegranskat)abstract
- Ruddlesden-Popper perovskites (RPPs), consisting of alternating organic spacer layers and inorganic layers, have emerged as a promising alternative to 3D perovskites for both photovoltaic and light-emitting applications. The organic spacer layers provide a wide range of new possibilities to tune the properties and even provide new functionalities for RPPs. However, the preparation of state-of-the-art RPPs requires organic ammonium halides as the starting materials, which need to be ex situ synthesized. A novel approach to prepare high-quality RPP films through in situ formation of organic spacer cations from amines is presented. Compared with control devices fabricated from organic ammonium halides, this new approach results in similar (and even better) device performance for both solar cells and light-emitting diodes. High-quality RPP films are fabricated based on different types of amines, demonstrating the universality of the approach. This approach not only represents a new pathway to fabricate efficient devices based on RPPs, but also provides an effective method to screen new organic spacers with further improved performance.
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| 26. |
- Qing, Jian, et al.
(författare)
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Spacer Cation Alloying in Ruddlesden-Popper Perovskites for Efficient Red Light-Emitting Diodes with Precisely Tunable Wavelengths
- 2021
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Ingår i: Advanced Materials. - : Wiley-V C H Verlag GMBH. - 0935-9648 .- 1521-4095. ; 33:49
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Tidskriftsartikel (refereegranskat)abstract
- Perovskite light-emitting diodes (PeLEDs) have recently shown significant progress with external quantum efficiencies (EQEs) exceeding 20%. However, PeLEDs with pure-red (620-660 nm) light emission, an essential part for full-color displays, remain a great challenge. Herein, a general approach of spacer cation alloying is employed in Ruddlesden-Popper perovskites (RPPs) for efficient red PeLEDs with precisely tunable wavelengths. By simply tuning the alloying ratio of dual spacer cations, the thickness distribution of quantum wells in the RPP films can be precisely modulated without deteriorating their charge-transport ability and energy funneling processes. Consequently, efficient PeLEDs with tunable emissions between pure red (626 nm) and deep red (671 nm) are achieved with peak EQEs up to 11.5%, representing the highest values among RPP-based pure-red PeLEDs. This work opens a new route for color tuning, which will spur future developments of pure-red or even pure-blue PeLEDs with high performance.
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| 27. |
- Qing, Jian, et al.
(författare)
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Spacer cation engineering in Ruddlesden-Popper perovskites for efficient red light-emitting diodes with recommendation 2020 color coordinates
- 2023
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Ingår i: Applied Surface Science. - : ELSEVIER. - 0169-4332 .- 1873-5584. ; 616
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Tidskriftsartikel (refereegranskat)abstract
- Ruddlesden-Popper perovskites (RPPs) have been demonstrated as a very promising approach for tuning the emission color of perovskite light-emitting diodes (PeLEDs). However, achieving high-performance red PeLEDs with recommendation 2020 color coordinates is still challenging due to the lack of reasonable control over the properties of RPP films. Here, we demonstrate that the judicious selection of spacer cations in RPPs affords a lever for engineering their film properties, including phase distribution, energy funneling process, trap density, and carrier mobility. Four structurally related spacer cations, benzylammonium (BZA), phenylethylammonium (PEA), 3-phenyl-1-propylammonium (PPA), and phenoxyethylammonium (POEA), are studied. Owing to narrow phase distribution, efficient energy funneling, and low trap density, the POEA-based RPP films enable efficient red PeLEDs with a peak external quantum efficiency of 10.3%, a maximum brightness of 1052 cd m- 2, and excellent spectral stability. Significantly, the electroluminescence spectrum represents CIE 1931 color coordinates of (0.71, 0.29), which meets the recommendation 2020 standard (0.708, 0.292). The findings provide useful guidelines for the rational design of new organic spacer cations for RPPs with high performance.
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| 28. |
- Ren, Luyao, et al.
(författare)
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Quartet DNA reference materials and datasets for comprehensively evaluating germline variant calling performance
- 2023
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Ingår i: Genome Biology. - : BioMed Central (BMC). - 1465-6906 .- 1474-760X. ; 24:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Genomic DNA reference materials are widely recognized as essential for ensuring data quality in omics research. However, relying solely on reference datasets to evaluate the accuracy of variant calling results is incomplete, as they are limited to benchmark regions. Therefore, it is important to develop DNA reference materials that enable the assessment of variant detection performance across the entire genome.RESULTS: We established a DNA reference material suite from four immortalized cell lines derived from a family of parents and monozygotic twins. Comprehensive reference datasets of 4.2 million small variants and 15,000 structural variants were integrated and certified for evaluating the reliability of germline variant calls inside the benchmark regions. Importantly, the genetic built-in-truth of the Quartet family design enables estimation of the precision of variant calls outside the benchmark regions. Using the Quartet reference materials along with study samples, batch effects are objectively monitored and alleviated by training a machine learning model with the Quartet reference datasets to remove potential artifact calls. Moreover, the matched RNA and protein reference materials and datasets from the Quartet project enables cross-omics validation of variant calls from multiomics data.CONCLUSIONS: The Quartet DNA reference materials and reference datasets provide a unique resource for objectively assessing the quality of germline variant calls throughout the whole-genome regions and improving the reliability of large-scale genomic profiling.
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| 29. |
- Wang, Feng, 1983-, et al.
(författare)
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Fundamentals of solar cells and light-emitting diodes
- 2019
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Ingår i: Advanced nanomaterials for solar cells and light emitting diodes. - Amsterdam : Elsevier. - 9780128136478 ; , s. 1-35
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter focuses on introducing basic concepts in solar cell and light-emitting diode (LED) devices. First, the fundamental knowledge about semiconductors and several important materials related to solar cells and LEDs is introduced to help the reader understand the working principle of devices. Second, we describe the working principle and basic terms involving solar cells, the energy loss processes, and several strategies for high-efficiency solar cell devices. Finally, we present the basic terms and the device structure of LEDs, as well as some approaches for high-efficiency white LEDs.
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| 30. |
- Wang, Heyong, et al.
(författare)
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Efficient Light-Emitting Diodes Based on In-Situ Self-Assembled Perovskite Nanocrystals
- 2018
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Ingår i: ORGANIC LIGHT EMITTING MATERIALS AND DEVICES XXII. - : SPIE-INT SOC OPTICAL ENGINEERING. - 9781510620445
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Konferensbidrag (refereegranskat)abstract
- We introduce a simple and low-cost approach -drop-coating method -for preparation of in-situ self-assembled perovskite nanocrystals for efficient light-emitting diodes. The PL spectrum of the self-assembled NFPI4 nanocrystals thin film prepared by the drop-coating method shows blue shift compared with that of the typical NFPI4 thin film prepared by spin-coating method. In addition, the PL spectra of these self-assembled nanocrystals are tuned from 765 nm to 725 nm by changing usage amounts of the perovskite precursor solution. More importantly, efficient light-emitting diodes with EQEs up to 6.8% are achieved based on these self-assembled NFPI4 nanocrystals.
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| 31. |
- Wang, Heyong, et al.
(författare)
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Efficient light-emitting diodes based on in-situ self-assembled perovskite nanocrystals
- 2018
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Ingår i: JOURNAL OF PHOTONICS FOR ENERGY. - : SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS. - 1947-7988. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- We introduce a simple and low-cost approach-drop-coating method-for preparation of in-situ self-assembled perovskite nanocrystals for efficient light-emitting diodes (LEDs). The photoluminescence (PL) spectrum of the self-assembled NFPI4 nanocrystals thin film prepared by the drop-coating method shows blue shift compared with that of the typical NFPI4 thin film prepared by the spin-coating method. In addition, the PL spectra of these self-assembled nanocrystals are tuned from 765 to 725 nm by changing usage amounts of the perovskite precursor solution. More importantly, efficient LEDs with external quantum efficiencies up to 6.8% are achieved based on these self-assembled NFPI4 nanocrystals. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)
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| 32. |
- Wang, Heyong, 1989-
(författare)
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High-Quality Perovskite Films for Efficient and Stable Light-Emitting Diodes
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Metal halide perovskites have attracted significant attention for light-emitting applications, because of their excellent properties, such as high photoluminescence quantum yields (PLQYs), good charge mobility, narrow emission bandwidth, readily tunable emission spectra ranging from ultraviolet to near-infrared, and solution processability. Since the first room-temperature perovskite-based light-emitting diodes (PeLEDs) reported in 2014, tremendous efforts have been made to promote the efficiencies of PeLEDs, including theoretical simulation, materials design, and device engineering. To reach the ultimate goal of commercialization, PeLEDs with both high-efficiency and long-term operational stability are desired. Achieving high-quality perovskite emissive films is key towards this goal. Centering around the high-quality perovskite films, in this thesis, we demonstrate effective synthesis strategies for the deposition of high-quality perovskite films (including both three-dimensional and mixed-dimensional perovskites) and investigate the effects of ion migration in the perovskite films on the performance of PeLEDs.Due to the fast crystallization nature of perovskites and the low formation energy of defects, controlling the crystallization processes of these films has proved to be an effective approach for achieving high-quality perovskite films. For three-dimensional (3D) perovskite films, we have controlled the formation of these films through the assistance of molecules with the amino group. Herein, we have chosen an electron-transport molecule with two amino groups, 4,4’-diaminodiphenyl sulfone (DDS), to control the crystallization process of perovskite films (Paper 1). The resulting perovskite films consists of in-situ formed high quality perovskite nanocrystals embedded in the electron-transport molecular matrix, resulting in improved PLQYs and structural stability. PeLEDs based on these perovskite films have exhibited both high efficiency and long operational stability.In addition, we have investigated the formation of mixed-dimensional perovskite films. Efficient PeLEDs based on mixed-dimensional perovskite films were fabricated with tin dioxide (SnO2) as an electron transport layer (Paper 3). We also note that the deposition methods have a significant impact on the morphology and optical properties of prepared mixed-dimensional perovskite films (Paper 4). In addition, we provide an effective method to extend the deposition of mixed-dimensional perovskite films, replacing organic ammonium halides with amines in the perovskite precursor solutions to form organic spacer cations through the in-situ protonation process of amines (Paper 2).In spite of these efforts, the performance of PeLEDs is still far from the commercialization standard, partially limited by ion migration. In Paper 5, we discuss impacts of mobile ions in the perovskite films on the performance of PeLEDs. We find that a dynamic redistribution of mobile ions can change current density of a device, leading to EQE/hysteresis during forward and reverse voltage scan and enhanced EQE under constant driving voltages. In addition, we have found that excess mobile ions in the perovskite layer can aggravate the hysteresis and shorten the operational stability of PeLEDs.In this thesis, we also discuss the remaining key challenges in the PeLED field, including the achievement of high-performance blue, white, and lead-free PeLEDs, as well as possible strategies to address these challenges. We hope that our research findings provide insights into the basic science behind the perovskite materials, and broadly benefit other optoelectronic communities, such as perovskite solar cells, flexible electronics, and so on.
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| 33. |
- Wang, Heyong, 1989-, et al.
(författare)
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Impacts of the Lattice Strain on Perovskite Light-Emitting Diodes
- 2023
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Ingår i: Advanced Energy Materials. - : Wiley-V C H Verlag GMBH. - 1614-6832 .- 1614-6840. ; 13:33
-
Tidskriftsartikel (refereegranskat)abstract
- The development of perovskite light-emitting diodes (PeLEDs) with both high efficiency and excellent stability remains challenging. Herein, a strong correlation between the lattice strain in perovskite films and the stability of resulting PeLEDs is revealed. Based on high-efficiency PeLEDs, the device lifetime is optimized by rationally tailoring the lattice strain in perovskite films. A PeLED with a high peak external quantum efficiency of 18.2% and a long lifetime of 151 h (T-70, under a current density of 20 mA cm(-2)) is realized with a minimized lattice strain in the perovskite film. In addition, an increase in the lattice strain is found during the long-time device stability test, indicating that the degradation of the local perovskite lattice structure could be one of the degradation mechanisms for long-term stable PeLEDs.
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| 34. |
- Wang, Kang, et al.
(författare)
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Luminescent metal-halide perovskites: fundamentals, synthesis, and light-emitting devices
- 2024
-
Ingår i: Science in China Series B. - : SCIENCE PRESS. - 1674-7291 .- 1869-1870. ; 67:6, s. 1776-1838
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Forskningsöversikt (refereegranskat)abstract
- Metal-halide perovskites have garnered considerable research attention as highly efficient light emitters in recent years due to their outstanding optoelectronic properties with remarkable tunability and excellent solution processabilities. Substantial advancements have been achieved in the development of novel halide perovskites, and the exploitations of these materials in light-emitting devices. This review comprehensively outlines recent breakthroughs in metal-halide perovskites, encompassing the rational design of perovskite materials with tunable light emission properties, the controllable growth of single crystal for a deeper understanding of their structure-property relationships, as well as the fundamental insights into the photophysics and carrier dynamics in perovskite systems. Additionally, it provides an overview of recent applications of perovskite materials in high-performance light-emitting diodes (LEDs) and lasers.
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| 35. |
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| 36. |
- Xu, Weidong, et al.
(författare)
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Precisely Controlling the Grain Sizes with an Ammonium Hypophosphite Additive for High-Performance Perovskite Solar Cells
- 2018
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Ingår i: Advanced Functional Materials. - : WILEY-V C H VERLAG GMBH. - 1616-301X .- 1616-3028. ; 28:33
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Tidskriftsartikel (refereegranskat)abstract
- A facile approach to precisely control the perovskite grain sizes is proposed and demonstrated for high-performance photovoltaic (PV) solar cells. With the introduction of various amounts of NH4H2PO2 (AHP) additives into the PbI2/CH3NH3I precursors, the grain scale of CH3NH3PbI3 films can be finely turned from hundreds of nanometer to micrometer scale, allowing evaluating the effects of crystalline grain boundary on trap densities, charge recombination, and PV device performance. The X-ray diffraction and X-ray photoelectron spectroscopy measurements indicate that the formation of intermediates plays a key role in assisting the perovskite crystal growth. The optimized devices show much larger open-circuit voltages (V-OC) up to 1.10 +/- 0.02 V and significantly enhance power conversion efficiencies (PCEs) of 16.5 +/- 0.7%, as compared to the control devices with PCE of 9.4 +/- 1.0% and V-OC of 1.00 +/- 0.03 V. Further investigations confirm that the boosted PV performance origins from the decreased defect densities due to enlarged grain sizes. It is also demonstrated that the approach is general and applicable to other perovskite systems, e.g., HC(NH2)(2)PbI3. The results suggest the promising application of AHP in achieving high-performance perovskite PV devices, and shed light on understanding the grain boundary effects on perovskite optoelectronics.
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| 37. |
- Yang, Fei, et al.
(författare)
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Efficient and Spectrally Stable Blue Perovskite Light-Emitting Diodes Based on Potassium Passivated Nanocrystals
- 2020
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Ingår i: Advanced Functional Materials. - : WILEY-V C H VERLAG GMBH. - 1616-301X .- 1616-3028. ; 30:10
-
Tidskriftsartikel (refereegranskat)abstract
- Metal halide perovskites have aroused tremendous interest in the past several years for their promising applications in display and lighting. However, the development of blue perovskite light-emitting diodes (PeLEDs) still lags far behind that of their green and red cousins due to the difficulty in obtaining high-quality blue perovskite emissive layers. In this study, a simple approach is conceived to improve the emission and electrical properties of blue perovskites. By introducing an alkali metal ion to occupy some sites of peripheral suspended organic ligands, the nonradiative recombination is suppressed, and, consequently, blue CsPb(Br/Cl)(3) nanocrystals with a high photoluminescence quantum efficiency of 38.4% are obtained. The introduced K+ acts as a new type of metal ligand, which not only suppresses nonradiative pathways but also improves the charge carrier transport of the perovskite nanocrystals. With further engineering of the device structure to balance the charge injection rate, a spectrally stable and efficient blue PeLED with a maximum external quantum efficiency of 1.96% at the emission peak of 477 nm is fabricated.
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| 38. |
- Yu, Hongling, et al.
(författare)
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Color-Stable Blue Light-Emitting Diodes Enabled by Effective Passivation of Mixed Halide Perovskites
- 2021
-
Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 12:26, s. 6041-6047
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Tidskriftsartikel (refereegranskat)abstract
- Bandgap tuning through mixing halide anions is one of the most attractive features for metal halide perovskites. However, mixed halide perovskites usually suffer from phase segregation under electrical biases. Herein, we obtain high-performance and color-stable blue perovskite LEDs (PeLEDs) based on mixed bromide/ chloride three-dimensional (3D) structures. We demonstrate that the color instability of CsPb(Br1-xClx)(3) PeLEDs results from surface defects at perovskite grain boundaries. By effective defect passivation, we achieve color-stable blue electroluminescence from CsPb(Br1-xClx)(3) PeLEDs, with maximum external quantum efficiencies of up to 4.5% and high luminance of up to 5351 cd m(-2) in the sky-blue region (489 nm). Our work provides new insights into the color instability issue of mixed halide perovskites and can spur new development of high-performance and color-stable blue PeLEDs.
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| 39. |
- Yu, Hongling, 1987-
(författare)
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Color Tuning for Perovskite Light-Emitting Diodes
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Metal halide perovskites (MHPs) are recognized as promising semiconductor materials for a variety of optical and electrical device applications due to their cost-effective and outstanding optoelectronic properties. As one of the most significant applications, perovskite light-emitting diodes (PeLEDs) hold promise for future lighting and display technologies, attributed to their high photoluminescence quantum yield (PLQY), high color purity, and tunable emission color. The emission colors of PeLEDs can be tuned by mixing the halide anions, adjusting the size of perovskite nanocrystals, or changing the dimensionality of perovskites. However, in practice, all these different approaches have their own advantages and challenges. This thesis centres around the color tunability of perovskites, aiming to develop PeLEDs with different colors using different approaches.We first demonstrate red and near-infrared PeLEDs using a straightforward approach – in situ solution-processed perovskite quantum dots (PQDs). PQDs prepared from colloidal approaches are widely reported and used in LEDs. In contrast, PQDs prepared from the in situ approaches are hardly reported, although they have advantages for device applications. By employing aromatic ammonium iodide (1-naphthylmethyl ammonium iodide, NMAI) as an agent into perovskite precursor solutions, together with annealing temperature modulation, we obtain in situ grown PQDs delivering high external quantum efficiencies (EQEs) of up to 11.0% with tunable electroluminescence (EL) spectra (667 - 790 nm). Our in situ generated PQDs based on pure-halogen perovskites can be easily obtained through a simple deposition process and free of phase segregation, making them a more promising approach for tuning the emission colors of perovskite LEDs.We then move to blue PeLEDs using cesium-based mixed-Br/Cl perovskites. Although mixed halides are a straightforward strategy to tune the emission color, PeLEDs based on this approach suffer from poor color stability, which is attributed to surface defects at grain boundaries. Under the condition of optical excitations, light density over a certain value (a threshold), oxygen, and surface defects at perovskite grain boundaries are found to be key factors inducing photoluminescence (PL) spectral instability of CsPb(Br1−xClx)3 perovskites. Upon electrical bias, defects at grain boundaries provide undesirable halide migration channels, responsible for EL spectral instability issues. Through effective defect passivation, the PL spectral resistance to oxygen is enhanced; moreover, high-performance and color-stable blue PeLEDs are achieved, delivering a maximum luminance of 5351 cd m–2 and a peak EQE of 4.55% with a peak emission wavelength at 489 nm. These findings provide new insights into the color instability issue of mixed halide blue perovskites, against which we also demonstrate an effective strategy.We finally realize single-emissive-layer (EML) white PeLEDs by employing a mixed halide perovskite film as the EML. In spite of high-performance monochromatic blue, green, and red colors, the development of white PeLEDs, especially for single-EML ones, remains a very big challenge. By effective modulation of the halide salt precursors, we achieve single-EML white PeLEDs with Commission Internationale de L’Eclairage (CIE) coordinates of (0.33, 0.33), close to those (0.3128, 0.3290) of the CIE standard illuminant D65. This work not only provides a successful demonstration of a single-EML white PeLED, but also provides useful guidelines for the future development of highperformance single-EML white PeLEDs.
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| 40. |
- Yu, Hongling, et al.
(författare)
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Efficient and Tunable Electroluminescence from In Situ Synthesized Perovskite Quantum Dots
- 2019
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Ingår i: Small. - : WILEY-V C H VERLAG GMBH. - 1613-6810 .- 1613-6829. ; 15:8
-
Tidskriftsartikel (refereegranskat)abstract
- Semiconductor quantum dots (QDs) are among the most promising next-generation optoelectronic materials. QDs are generally obtained through either epitaxial or colloidal growth and carry the promise for solution-processed high-performance optoelectronic devices such as light-emitting diodes (LEDs), solar cells, etc. Herein, a straightforward approach to synthesize perovskite QDs and demonstrate their applications in efficient LEDs is reported. The perovskite QDs with controllable crystal sizes and properties are in situ synthesized through one-step spin-coating from perovskite precursor solutions followed by thermal annealing. These perovskite QDs feature size-dependent quantum confinement effect (with readily tunable emissions) and radiative monomolecular recombination. Despite the substantial structural inhomogeneity, the in situ generated perovskite QDs films emit narrow-bandwidth emission and high color stability due to efficient energy transfer between nanostructures that sweeps away the unfavorable disorder effects. Based on these materials, efficient LEDs with external quantum efficiencies up to 11.0% are realized. This makes the technologically appealing in situ approach promising for further development of state-of-the-art LED systems and other optoelectronic devices.
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| 41. |
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| 42. |
- Zhang, Jiangbin, et al.
(författare)
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Efficient non-fullerene organic solar cells employing sequentially deposited donor-acceptor layers
- 2018
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Ingår i: Journal of Materials Chemistry A. - : ROYAL SOC CHEMISTRY. - 2050-7488 .- 2050-7496. ; 6:37, s. 18225-18233
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Tidskriftsartikel (refereegranskat)abstract
- Non-fullerene acceptors (NFAs) have recently outperformed their fullerene counterparts in binary bulk-heterojunction (BHJ) organic solar cells (OSCs). Further development of NFA OSCs may benefit other novel OSC device structures that alter or extend the standard BHJ concept. Here, we report such a new processing route that forms a BHJ-like morphology between sequentially processed polymer donor and NFA with high power conversion efficiencies in excess of 10%. Both devices show similar charge generation and recombination behaviours, supporting formation of similar BHJ active layers. We correlate the approximate to 30 meV smaller open-circuit voltage in sq-BHJ devices to more substantial non-radiative recombination by voltage loss analysis. We also determine the exciton diffusion length of benchmark polymer PBDB-T to be 10 +/- 3 nm. Our results demonstrate high-efficiency OSC devices using sequential deposition method and provide new opportunities to further improve performance of state-of-the-art OSCs.
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| 43. |
- Zhang, Jia, et al.
(författare)
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Transport Layer Engineering Toward Lower Threshold for Perovskite Lasers
- 2023
-
Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 35:30
-
Tidskriftsartikel (refereegranskat)abstract
- Charge-transport layers are essential for achieving electrically pumped perovskite lasers. However, their role in perovskite lasing is not fully understood. Here, the role of charge-transport layers on the lasing actions of perovskite films is explored by investigating the amplified spontaneous emission (ASE) thresholds. A largely reduced ASE threshold and enhanced ASE intensity is demonstrated by introducing an additional hole transport layer poly(triaryl amine) (PTAA). It is shown that the key role of the PTAA layer is to accelerate the hot-carrier cooling process by extracting holes in perovskites. With reduced hot holes, the Auger recombination loss is largely suppressed, resulting in decreased ASE threshold. This argument is further supported by the fact that the ASE threshold can be further reduced from 25.7 to 7.2 mu J cm(-2) upon switching the pumping wavelength from 400 to 500 nm to directly avoid excess hot-hole generation. This work exemplifies how to further reduce the ASE threshold with transport layer engineering through hot-hole manipulation. This is critical to maintaining the excellent gain properties of perovskites when integrating them into electrical devices, paving the way for electrically pumped perovskite lasers.
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| 44. |
- Zhang, Liangdong, et al.
(författare)
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Bright Free Exciton Electroluminescence from Mn-Doped Two-Dimensional Layered Perovskites
- 2019
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Ingår i: The Journal of Physical Chemistry Letters. - : AMER CHEMICAL SOC. - 1948-7185. ; 10:11, s. 3171-3175
-
Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional (2D) perovskites incorporating hydrophobic organic spacer cations show improved film stability and morphology compared to their three-dimensional (3D) counterparts. However, 2D perovskites usually exhibit low photoluminescence quantum efficiency (PLQE) owing to strong exciton-phonon interaction at room temperature, which limits their efficiency in light-emitting diodes (LEDs). Here, we demonstrate that the device performance of 2D perovskite LEDs can be significantly enhanced by doping Mn(2+)in (benzimidazolium)(2)PbI4 2D perovskite films to suppress the exciton-phonon interaction. The distorted [PbI6](4-) octahedra by Mn-doping and the rigid benzimidazolium (BIZ) ring without branched chains in the 2D perovskite structure lead to improved crystallinity and rigidity of the perovskites, resulting in suppressed phonon-exciton interaction and enhanced PLQE. On the basis of this strategy, for the first time, we report yellow electroluminescence from free excitons in 2D (n = 1) perovskites with a maximum brightness of 225 cd m(-2) and a peak EQE of 0.045%.
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