| 1. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Fan, Qunping, et al.
(författare)
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Unidirectional Sidechain Engineering to Construct Dual-Asymmetric Acceptors for 19.23 % Efficiency Organic Solar Cells with Low Energy Loss and Efficient Charge Transfer
- 2023
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Ingår i: Angewandte Chemie International Edition. - : WILEY-V C H VERLAG GMBH. - 1433-7851 .- 1521-3773. ; 62:36
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Tidskriftsartikel (refereegranskat)abstract
- Achieving both high open-circuit voltage (V-oc) and short-circuit current density (J(sc)) to boost power-conversion efficiency (PCE) is a major challenge for organic solar cells (OSCs), wherein high energy loss (E-loss) and inefficient charge transfer usually take place. Here, three new Y-series acceptors of mono-asymmetric asy-YC11 and dual-asymmetric bi-asy-YC9 and bi-asy-YC12 are developed. They share the same asymmetric D(1)AD(2) (D-1=thieno[3,2-b]thiophene and D-2=selenopheno[3,2-b]thiophene) fused-core but have different unidirectional sidechain on D-1 side, allowing fine-tuned molecular properties, such as intermolecular interaction, packing pattern, and crystallinity. Among the binary blends, the PM6 : bi-asy-YC12 one has better morphology with appropriate phase separation and higher order packing than the PM6 : asy-YC9 and PM6 : bi-asy-YC11 ones. Therefore, the PM6 : bi-asy-YC12-based OSCs offer a higher PCE of 17.16 % with both high V-oc and J(sc), due to the reduced E-loss and efficient charge transfer properties. Inspired by the high V-oc and strong NIR-absorption, bi-asy-YC12 is introduced into efficient binary PM6 : L8-BO to construct ternary OSCs. Thanks to the broadened absorption, optimized morphology, and furtherly minimized E-loss, the PM6 : L8-BO : bi-asy-YC12-based OSCs achieve a champion PCE of 19.23 %, which is one of the highest efficiencies among these annealing-free devices. Our developed unidirectional sidechain engineering for constructing bi-asymmetric Y-series acceptors provides an approach to boost PCE of OSCs.
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| 3. |
- Ji, Fuxiang, 1991-
(författare)
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Bandgap Engineering of Lead-Free Halide Double Perovskites
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lead-free halide double perovskites (HDPs, A2BIBIIIX6) with attractive optical and electronic features are regarded as one of the most promising alternatives to overcome the toxicity and stability issues of lead halide perovskites. They provide a wide range of possible combinations and rich substitutional chemistry with interesting properties for various optoelectronic devices. However, the performance of state-of-the-art lead-free HDPs is not yet comparable to that of lead halide perovskites, especially in the photovoltaic field. One of the main reasons for this is that HDPs usually have large and/or indirect bandgaps, which limit their optical and optoelectronic properties in the visible and infrared region. In this thesis, we attempt to modify the bandgap and optical properties of HDPs using metal doping/alloying and crystallization control, as well as provide detailed understanding of the alloying at the atomic level. We also observe significant changes of the bandgap of HDPs at different temperatures (i.e., thermochromism) and uncover the reasons behind it. We first adopt the metal doping/alloying strategy to alter the absorption properties of benchmark HDPs Cs2AgBiBr6. By introducing Cu as the dopant in Cs2AgBiBr6, we significantly broaden the absorption edge from around 610 nm to around 860 nm. Systematic characterizations indicate that Cu doping introduces defect states (sub-bandgap states) in the bandgap, without changing the bandgap of Cs2AgBiBr6. Interestingly, these sub-bandgaps can generate considerable amount of band carriers upon optical excitation, making these double perovskites promising for near-infrared light detection. In parallel with the material modification using the metal doping/alloying strategy, the fundamental understanding of these doped/alloyed double perovskite is also of critical importance. In the second paper, we reveal the atomic-level structure of alloyed double perovskites by presenting a series of double perovskite alloys with the chemical formula Cs2AgIn1-xFexCl6 (x = 0-1) showing tunable bandgaps in the range of 2.8-1.6 eV. Our results show that Fe3+ substitutes In3+ in the lattice with the formation of [FeCl6]3−·[AgCl6]5− domains, which grow larger gradually as the Fe3+ concentration increases. It is noted that these domains could be further connected to form microscopically segregated Fe3+-rich phases in the double perovskite alloys. To narrow the bandgap of Cs2AgBiBr6, we also develop a crystallization control approach, where high temperature is employed to assist the single crystal growth. By simply increasing the crystal growth temperature from 60 oC to 150 oC, the bandgap of Cs2AgBiBr6 crystals can be reduced from 1.98 eV to 1.72 eV, which is the lowest reported bandgap for Cs2AgBiBr6 at ambient conditions. The underlying reason is hypothesized to be related to the increased level of Ag–Bi disorder in the crystal structure. Lastly, we observe an interesting reversible thermochromic behavior in HDPs Cs2NaFeCl6. Specifically, the optical bandgap of Cs2NaFeCl6 is reduced from 2.06 eV to 1.86 eV when the temperature increases from RT to 150 oC and turns back to its original value after cooling. Meanwhile, we observe lattice expansion during the heating/ cooling process without phase transition. Our first-principles calculation indicates that the underlying mechanism for the thermochromic phenomenon in Cs2NaFeCl6 is mainly related to the electron-phonon coupling. Although the development of HDPs is in its early stages, we believe that HDPs with impressive optical and electronic properties and rich substitutional chemistry have a bright future in optoelectronic and multifunctional applications. Our findings shed new light to the absorption and bandgap modulation of HDPs and provide new insights into the atomic-level structures of DPAs, which can help to develop efficient optoelectronic devices.
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| 4. |
- Ji, Fuxiang, 1991-, et al.
(författare)
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Challenges and Progress in Lead-Free Halide Double Perovskite Solar Cells
- 2023
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Ingår i: Solar RRL. - : John Wiley & Sons. - 2367-198X. ; 7:6
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Tidskriftsartikel (refereegranskat)abstract
- Lead-free halide double perovskites (HDPs) with a chemical formula of A(2)B(+)B(3+)X(6) are booming as attractive alternatives to solve the toxicity issue of lead-based halide perovskites (APbX(3)). HDPs show excellent stability, a wide range of possible combinations, and attractive optoelectronic features. Although a number of novel HDPs have been studied, the power conversion efficiency of the state-of-the-art double perovskite solar cell is still far inferior to that of the dominant Pb-based ones. Understanding the fundamental challenges is essential for further increasing device efficiency. In this review, HDPs with attractive electronic and optical properties are focused on, and current challenges in material properties and device fabrication that limit high-efficiency photovoltaics are analyzed. Finally, the promising approaches and views to overcome these bottlenecks are highlighted.
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| 5. |
- Ji, Fuxiang, 1991-, et al.
(författare)
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Remarkable Thermochromism in the Double Perovskite Cs2NaFeCl6
- 2023
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Ingår i: Advanced Optical Materials. - : Wiley-Blackwell. - 2162-7568 .- 2195-1071.
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Tidskriftsartikel (refereegranskat)abstract
- Lead-free halide double perovskites (HDPs) have emerged as a new generation of thermochromic materials. However, further materials development and mechanistic understanding are required. Here, a highly stable HDP Cs2NaFeCl6 single crystal is synthesized, and its remarkable and fully reversible thermochromism with a wide color variation from light-yellow to black over a temperature range of 10 to 423 K is investigated. First-principles, density functional theory (DFT)-based calculations indicate that the thermochromism in Cs2NaFeCl6 is an effect of electron–phonon coupling. The temperature sensitivity of the bandgap in Cs2NaFeCl6 is up to 2.52 meVK−1 based on the Varshni equation, which is significantly higher than that of lead halide perovskites and many conventional group-IV, III–V semiconductors. Meanwhile, this material shows excellent environmental, thermal, and thermochromic cycle stability. This work provides valuable insights into HDPs' thermochromism and sheds new light on developing efficient thermochromic materials.
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| 6. |
- Ji, Fuxiang, 1991-, et al.
(författare)
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Remarkable Thermochromism in the Double Perovskite Cs2NaFeCl6
- 2024
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Ingår i: Advanced Optical Materials. - : John Wiley & Sons. - 2162-7568 .- 2195-1071. ; 12:8
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Tidskriftsartikel (refereegranskat)abstract
- Lead-free halide double perovskites (HDPs) have emerged as a new generation of thermochromic materials. However, further materials development and mechanistic understanding are required. Here, a highly stable HDP Cs2NaFeCl6 single crystal is synthesized, and its remarkable and fully reversible thermochromism with a wide color variation from light-yellow to black over a temperature range of 10 to 423 K is investigated. First-principles, density functional theory (DFT)-based calculations indicate that the thermochromism in Cs2NaFeCl6 is an effect of electron-phonon coupling. The temperature sensitivity of the bandgap in Cs2NaFeCl6 is up to 2.52 meVK(-1) based on the Varshni equation, which is significantly higher than that of lead halide perovskites and many conventional group-IV, III-V semiconductors. Meanwhile, this material shows excellent environmental, thermal, and thermochromic cycle stability. This work provides valuable insights into HDPs' thermochromism and sheds new light on developing efficient thermochromic materials.
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| 7. |
- Ma, Ruijie, et al.
(författare)
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All-polymer solar cells with over 16% efficiency and enhanced stability enabled by compatible solvent and polymer additives
- 2022
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Ingår i: Aggregate. - : Wiley. - 2692-4560 .- 2766-8541. ; 3:3
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Tidskriftsartikel (refereegranskat)abstract
- Considering the robust and stable nature of the active layers, advancing the power conversion efficiency (PCE) has long been the priority for all-polymer solar cells (all-PSCs). Despite the recent surge of PCE, the photovoltaic parameters of the state-of-the-art all-PSC still lag those of the polymer:small molecule-based devices. To compete with the counterparts, judicious modulation of the morphology and thus the device electrical properties are needed. It is difficult to improve all the parameters concurrently for the all-PSCs with advanced efficiency, and one increase is typically accompanied by the drop of the other(s). In this work, with the aids of the solvent additive (1-chloronaphthalene) and the n-type polymer additive (N2200), we can fine-tune the morphology of the active layer and demonstrate a 16.04% efficient all-PSC based on the PM6:PY-IT active layer. The grazing incidence wide-angle X-ray scattering measurements show that the shape of the crystallites can be altered, and the reshaped crystallites lead to enhanced and more balanced charge transport, reduced recombination, and suppressed energy loss, which lead to concurrently improved and device efficiency and stability.
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| 8. |
- Wang, Feng, et al.
(författare)
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Defects engineering for high-performance perovskite solar cells
- 2018
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Ingår i: npj Flexible Electronics. - : Nature Publishing Group. - 2397-4621. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- Metal halide perovskites have achieved great success in photovoltaic applications during the last few years. The solar to electrical power conversion efficiency (PCE) of perovskite solar cells has been rapidly improved from 3.9% to certified 22.7% due to the extensive efforts on film deposition methods, composition and device engineering. Further investigation on eliminating the defect states in perovskite absorbers is necessary to push forward the PCE of perovskite solar cells approaching the Shockley-Queisser limit. In this review, we summarize the defect properties in perovskite films and present methodologies to control the defects density, including the growth of large size crystals, photo-curing method, grain boundary and surface passivation, and modification of the substrates. We also discuss the defects-related stability and hysteresis issues and highlight the current challenges and opportunities in defects control of perovskite films.
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| 9. |
- 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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| 10. |
- 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
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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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| 11. |
- Argillander, Joakim, et al.
(författare)
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Quantum random number generation based on a perovskite light emitting diode
- 2023
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Ingår i: Communications Physics. - : NATURE PORTFOLIO. - 2399-3650. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- True random number generation is not thought to be possible using a classical approach but by instead exploiting quantum mechanics genuine randomness can be achieved. Here, the authors demonstrate a certified quantum random number generation using a metal-halide perovskite light emitting diode as a source of weak coherent polarisation states randomly producing an output of either 0 or 1. The recent development of perovskite light emitting diodes (PeLEDs) has the potential to revolutionize the fields of optical communication and lighting devices, due to their simplicity of fabrication and outstanding optical properties. Here we demonstrate that PeLEDs can also be used in the field of quantum technologies by implementing a highly-secure quantum random number generator (QRNG). Modern QRNGs that certify their privacy are posed to replace classical random number generators in applications such as encryption and gambling, and therefore need to be cheap, fast and with integration capabilities. Using a compact metal-halide PeLED source, we generate random numbers, which are certified to be secure against an eavesdropper, following the quantum measurement-device-independent scenario. The obtained generation rate of more than 10 Mbit s(-1), which is already comparable to commercial devices, shows that PeLEDs can work as high-quality light sources for quantum information tasks, thus opening up future applications in quantum technologies.
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| 12. |
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| 13. |
- Bao, Qinye, et al.
(författare)
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Regular Energetics at Conjugated Electrolyte/Electrode Modifier for Organic Electronics and Their Implications of Design Rules
- 2015
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Ingår i: Advanced Materials Interfaces. - : John Wiley & Sons. - 2196-7350. ; 2:12, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- Regular energetics at a conjugated electrolyte/electrode modifier are found and controlled by equilibration of the Fermi level and an additional interface double dipole step induced by ionic functionality. Based on the results, design rules for conjugated electrolyte/electrode modifiers to achieve the smallest charge injection/exaction barrier and break through the current thickness limitation are proposed.
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| 14. |
- Bian, Qingzhen, 1988-
(författare)
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Excitonic and charge carrier transport in organic materials and device applications
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the potential for future commercial use, organic electronics have been intensively studied for the last few decades. To exploit the next generation of high-performance devices, detailed study of the underlying physics is essential. Excitonic and charge carrier transport plays a critical role in device performance and related studies have attracted a lot of attention in recent decades. This thesis particularly focused on excitonic and charge carrier transport in organic materials and related device applications.In natural light harvesting systems, such as the reaction centers of purple bacteria, quantum coherence has been proposed to be present as a contributor to the related charge and energy transport processes, and almost 100% charge conversion is present in these efficient biological systems. This high energy conversion efficiency inspires the idea that if a similar strategy was used in artificial energy conversion devices such as organic photovoltaics, etc., this could significantly enhance the device’s performance. In the first study, the charge separation process in some donor/acceptor blends was investigated. The contribution of quantum coherence to device performance was studied in detail using several steady state and ultrafast transient techniques. In one efficient donor/acceptor blend, a pronounced coherence of charge separation was identified, which contributed to the enhancement of the photocurrent generation, which finally resulted in efficient device performance.For the light emitting diodes, triplet excitons harvesting plays a critical role in device performance. In the thermally activated delayed fluorescence (TADF) materials, due to an efficient reverse intersystem process from triplet excitons to singlet excitons, the losses due to triplet excitons were suppressed. As a result, a desired high quantum yield has been achieved. To enhance device efficiency, the detailed study of the upconversion physics between triplet and singlet is needed. Previous studies have proposed some physical models to explain this efficient upconversion process, while the nature of this physical process is still under debate and unclear. In my second work, we studied the exciton kinetics in two different TADF materials. These TADF materials were inserted in a protein fibril host, and the resulting protein scaffold was able to modify the geometric configuration of the related TADF molecule. As a result, an enhancement of the photoluminescence quantum yield was achieved.To achieve efficient device performance in organic electronics, the physical processes at the metal/material interface and charge carrier injection/extraction, also play a critical role. Efficient charge injection can be achieved by Ohmic contact, and charge injection/extraction of metal/organic materials has been intensively studied in the last few decades. In my third study, an efficient hole transport material based on the biopolymer DNA was introduced. A hole doping process was found in the hybrid materials and contributes to the Ohmic contacts. The hybrid material can be used in different organic electronics devices, such as field effect transistors, light emitting diodes and solar cells, and thus demonstrates a general application capability.In organic photovoltaics, the loss from the open circuit photovoltages has been an Achilles’ heel for further enhancement of device performance. The voltage loss includes the radiative and non-radiative value, and intensive studies have focused on how to suppress losses from the non-radiative channel. In my fourth study, the non-radiative voltage loss was studied in a series of terpolymer blends and ternary blends. Compared to the ternary blends, a decreased nonradiative loss was found in the terpolymer blends.
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| 15. |
- Cai, Weidong, 1991-, et al.
(författare)
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Chirality Induced Crystal Structural Difference in Metal Halide Composites
- 2022
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Ingår i: Advanced Optical Materials. - : Wiley-V C H Verlag GMBH. - 2162-7568 .- 2195-1071. ; 10:16
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Tidskriftsartikel (refereegranskat)abstract
- Incorporating chiral organic compounds into metal halide frames is a common and useful method to introduce chirality in metal halide composites. The structures of resulting racemic and chiral composites are usually considered to be nearly identical owing to similar chemical bonding. In this work, by incorporating chiral MBABr (bromide methylbenzylamine) into an inorganic frame, a significant crystallization difference between the resulting racemic and chiral metal halide composites is observed, as confirmed by both structural and spectroscopic measurements. In addition, the structural transformation in the chiral composites can also be induced by moisture, ascribed to the asymmetric hydrogen bonding in chiral materials. These results provide new insights for the future synthesis of chiral materials and open up new possibilities to advance the materials functionalities.
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| 16. |
- Cai, Weidong, 1991-
(författare)
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Tunning Multicolor Light Emission in Lead-free Materials
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Perovskites are a class of compounds with the general formula ABX3 and becoming increasingly attractive recently. Because this kind of material possesses various advantages such as abundant raw materials, easy synthesis, excellent photoelectric properties, and short production process. As one of the applications for lead-based perovskites, the perovskite solar cells have quickly enhanced their PCE from 3.8% in 2009 to over 25% within a short period. However, the problems, such as instability of the ionic crystal nature and toxicity of lead, largely hinder the lead-based perovskites towards commercialization. Therefore, it is necessary to develop new lead-free materials as alternative to lead-based perovskites, where similar structures can be formed to inherit the excellent optoelectronic properties. Moreover, new properties can be achieved due to more abundant metal candidates in lead-free materials. Based on this, we develop different kinds of perovskite-structure-like lead-free materials such as organic inorganic hybrid materials, chiral materials and double perovskites. In addition to physical and chemical properties like photoluminescence, absorption, structure, etc., we further demonstrate their potential applications according to their unique properties such as multicolor light emission.We incorporate chiral MBA (methylbenzylamine) in inorganic metal system to obtain chiral lead-free organic inorganic hybrid materials, where significant crystallization difference is observed between rac and chiral halide compounds for the first time. Such difference is confirmed by spectrum and structural results. What’s more, we find that moisture can cause the structural transfer in chiral compounds, attributed to the asymmetric hydrogen bonding of chiral compounds. Our achievements open up new chance to improve our material property and provide new horizon for synthesis of chiral materials in the future.Then, we obtained blue emission center in Mn-based organic and inorganic compounds by choosing organic molecule MBA. The method has basic difference with the emissions in Mn based compounds. The coexisting two emission centers of our Mn based samples is verified by spectral results. Because two emission centers can induce different PL excitation responses, so that the excitation wavelengths are capable of manipulating the emission color. Specifically, we achieve CIE coordinates of (0.33, 0.35) with a white emission. The potential of our materials in anti-counterfeiting and multicolor lighting technology are further demonstrated. Our accomplishments explore a new approach for multicolor emission in Mn based materials.We finally obtained Sb3+/Cu+ co-doped Cs2NaInCl6 (CNIC) double perovskite by hydrothermal reaction which exhibits tunable dual emissions with PL quantum efficiency (PLQE) of 78%. Depending on different photoluminescence excitation (PLE) spectra between two emissions, multiple emission colors can be got by manipulating excitation wavelength. Interestingly, emission color gamut can be further tuned through manipulating the feeding ratio of CuI dopant, where warm color and cool color can be achieved separately. We further illustrated the application potential of our co-doped materials in the fileds of multicolor lighting devices and anti-counterfeiting. Our achievements open up a brand-new strategy for wider spectral luminescence of double perovskites and pace up the road for a series of new applications.
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| 17. |
- Chen, Desui, et al.
(författare)
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Shelf-Stable Quantum-Dot Light-Emitting Diodes with High Operational Performance
- 2020
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Ingår i: Advanced Materials. - : Wiley-VCH Verlagsgesellschaft. - 0935-9648 .- 1521-4095. ; 32
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Tidskriftsartikel (refereegranskat)abstract
- Quantum-dot light-emitting diodes (QLEDs) promise a new generation of high-performance, large-area, and cost-effective electroluminescent devices for both display and solid-state lighting technologies. However, a positive ageing process is generally required to improve device performance for state-of-the-art QLEDs. Here, it is revealed that the in situ reactions induced by organic acids in the commonly used encapsulation acrylic resin lead to positive ageing and, most importantly, the progression of in situ reactions inevitably results in negative ageing, i.e., deterioration of device performance after long-term shelf storage. In-depth mechanism studies focusing on the correlations between the in situ chemical reactions and the shelf-ageing behaviors of QLEDs inspire the design of an electron-transporting bilayer, which delivers both improved electrical conductivity and suppressed interfacial exciton quenching. This material innovation enables red QLEDs exhibiting neglectable changes of external quantum efficiency (>20.0%) and ultralong operational lifetime (T-95: 5500 h at 1000 nits) after storage for 180 days. This work provides design principles for oxide electron-transporting layers to realize shelf-stable and high-operational-performance QLEDs, representing a new starting point for both fundamental studies and practical applications.
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| 18. |
- Chen, Haoran, et al.
(författare)
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Decoupling engineering of formamidinium-cesium perovskites for efficient photovoltaics
- 2022
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Ingår i: National Science Review. - : Oxford University Press. - 2095-5138 .- 2053-714X. ; 9:10
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Tidskriftsartikel (refereegranskat)abstract
- Sequential Cs incorporation strategy is developed to decouple crystallization of FACs perovskite with reduced electron-phonon coupling, resulting in highly stable FACs tri-iodide perovskite photovoltaics with record efficiency. Although pure formamidinium iodide perovskite (FAPbI(3)) possesses an optimal gap for photovoltaics, their poor phase stability limits the long-term operational stability of the devices. A promising approach to enhance their phase stability is to incorporate cesium into FAPbI(3). However, state-of-the-art formamidinium-cesium (FA-Cs) iodide perovskites demonstrate much worse efficiency compared with FAPbI(3), limited by the different crystallization dynamics of formamidinium and cesium, which result in poor composition homogeneity and high trap densities. We develop a novel strategy of crystallization decoupling processes of formamidinium and cesium via a sequential cesium incorporation approach. As such, we obtain highly reproducible, highly efficient and stable solar cells based on FA(1)(-)(x)Cs(x)PbI(3) (x = 0.05-0.16) films with uniform composition distribution in the nanoscale and low defect densities. We also revealed a new stabilization mechanism for Cs doping to stabilize FAPbI(3), i.e. the incorporation of Cs into FAPbI(3) significantly reduces the electron-phonon coupling strength to suppress ionic migration, thereby improving the stability of FA-Cs-based devices.
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| 19. |
- 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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| 20. |
- Cui, Yong, et al.
(författare)
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Accurate photovoltaic measurement of organic cells for indoor applications
- 2021
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Ingår i: Joule. - : CELL PRESS. - 2542-4351. ; 5:5, s. 1016-1023
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Photovoltaic (PV) cells offer a convenient energy source to drive micropower electronic devices for indoor applications. However, it is challenging to measure the power conversion efficiency (PCE) of PV cells under indoor lighting and the PV community lacks a feasible and accurate measurement protocol. Here, we start with the fundamental parameters which determine the PCE, and carefully design a series of experiments to examine the origins which might cause measurement errors for organic PV measurements under indoor lighting. We demonstrate the critical importance of: 1, temporal stability and spatial homogeneity of the light sources, 2, calibration of the spectral irradiance and illuminations of the light sources, 3, the area of the cells (1 cm2 or large cells are preferred), 4, the aperture of the mask (an aperture slightly smaller than the cell area is preferred), and 5, stray lights from the measurement environment. Based on these careful investigations, we suggest a feasible measurement method, by which accurate measurement of the indoor PV efficiency is made possible. Our study will promote the healthy development of indoor PV technology for practical applications.
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| 21. |
- Fan, Qunping, 1989, et al.
(författare)
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High-performance all-polymer solar cells enabled by a novel low bandgap non-fully conjugated polymer acceptor
- 2021
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Ingår i: Science in China Series B. - : Springer Nature. - 1674-7291 .- 1869-1870. ; 64, s. 1380-1388
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Tidskriftsartikel (refereegranskat)abstract
- Anon-fully conjugated polymer as a new class of acceptor materials has shown some advantages over its small molecular counterpart when used in photoactive layers for all-polymer solar cells (all-PSCs), despite a low power conversion efficiency (PCE) caused by its narrow absorption spectra. Herein, a novel non-fully conjugated polymer acceptor PFY-2TS with a low bandgap of similar to 1.40 eV was developed, via polymerizing a large pi-fused small molecule acceptor (SMA) building block (namely YBO) with a non-conjugated thioalkyl linkage. Compared with its precursor YBO, PFY-2TS retains a similar low bandgap but a higher LUMO level. Moreover, compared with the structural analog of YBO-based fully conjugated polymer acceptor PFY-DTC, PFY-2TS shows similar absorption spectrum and electron mobility, but significantly different molecular crystallinity and aggregation properties, which results in optimal blend morphology with a polymer donor PBDB-T and better device physical processes in all-PSCs. As a result, PFY-2TS-based all-PSCs achieved a PCE of 12.31% with a small energy loss of 0.56 eV enabled by the reduced non-radiative energy loss (0.24 eV), which is better than that of 11.08% for the PFY-DTC-based ones. Our work clearly demonstrated that non-fully conjugated polymers as a new class of acceptor materials are very promising for the development of high-performance all-PSCs.
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| 22. |
- Gao, Jingfang, 1966-, et al.
(författare)
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Association of NFKBIA polymorphism with colorectal cancer risk and prognosis in Swedish and Chinese populations
- 2007
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Ingår i: Scandinavian Journal of Gastroenterology. - : Informa UK Limited. - 0036-5521 .- 1502-7708. ; 42:3, s. 345-350
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Tidskriftsartikel (refereegranskat)abstract
- Objective. The inhibitory proteins, IκBs, regulate the activity of nuclear factor kappa-beta (NF-κB), which is implicated in tumorigenesis by regulating expression of a variety of genes involved in cellular transformation, proliferation, invasion, angiogenesis and metastasis. Variants in the genes encoding IκBs may be involved in cancer development through the activation of NF-κB. The objective of this study was to investigate the susceptibility of an A to G variation (rs696) in the 3′ UTR of NFKBIA (encoding IκBα) to colorectal cancer (CRC) and the association of this polymorphism with clinicopathologic variables in CRC patients. Material and methods. A case-control study was carried out on a Swedish (155 CRCs, 438 controls) and a Chinese population (199 CRCs, 577 controls). The genotype of NFKBIA was determined by PCR-restriction fragment length polymorphism. Results. The frequency of the AG genotype was increased in the Chinese patients ≥50 years of age compared with the Chinese controls (odds ratio (OR) = 3.06, 95% confidence interval (CI) = 1.55-6.02, p=0.001), even when adjusted for age (OR = 3.20, 95% CI = 1.61-6.38, p=0.001). The GG genotype of NFKBIA was related to a poorer survival rate in the Swedish patients, independent of gender, age, tumour location, Dukes' stage and differentiation (hazard ratio = 3.10, 95% Cl = 1.28-7.60, p=0.01). Conclusions. Chinese individuals ≥50 years of age carrying the AG genotype of NFKBIA may be at an increased risk of developing CRC, and the GG genotype of NFKBIA may be considered as a prognostic factor for Swedish CRC patients. © 2007 Taylor & Francis.
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| 23. |
- Hou, Jianhui, et al.
(författare)
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Organic solar cells based on non-fullerene acceptors
- 2018
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Ingår i: Nature Materials. - : Nature Publishing Group. - 1476-1122 .- 1476-4660. ; 17:2, s. 119-128
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Forskningsöversikt (refereegranskat)abstract
- Organic solar cells (OSCs) have been dominated by donor: acceptor blends based on fullerene acceptors for over two decades. This situation has changed recently, with non-fullerene (NF) OSCs developing very quickly. The power conversion efficiencies of NF OSCs have now reached a value of over 13%, which is higher than the best fullerene-based OSCs. NF acceptors show great tunability in absorption spectra and electron energy levels, providing a wide range of new opportunities. The coexistence of low voltage losses and high current generation indicates that new regimes of device physics and photophysics are reached in these systems. This Review highlights these opportunities made possible by NF acceptors, and also discuss the challenges facing the development of NF OSCs for practical applications.
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| 24. |
- Huang, Yuting, et al.
(författare)
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Host-Guest Strategy Enabling Nonhalogenated Solvent Processing for High-Performance All-Polymer Hosted Solar Cells
- 2023
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Ingår i: Chinese journal of chemistry. - : WILEY-V C H VERLAG GMBH. - 1001-604X .- 1614-7065. ; 41:9, s. 1066-1074
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Tidskriftsartikel (refereegranskat)abstract
- The power conversion efficiencies (PCEs) of all-polymer solar cells (all-PSCs), usually processed from low-boiling-point and toxic solvents, have reached high values of 18%. However, poor miscibility and uncontrollable crystallinity in polymer blends lead to a notable drop in the PCEs when using green solvents, limiting the practical development of all-PSCs. Herein, a third component (guest) BTO was employed to optimize the miscibility and enhance the crystallinity of PM6/PY2Se-F host film processed from green solvent toluene (TL), which can effectively suppress the excessive aggregation of PY2Se-F and facilitate a nano-scale interpenetrating network morphology for exciton dissociation and charge transport. As a result, TL-processed all-polymer hosted solar cells (all-PHSCs) exhibited an impressive PCE of 17.01%. Moreover, the strong molecular interaction between the host and guest molecules also enhances the thermal stability of the devices. Our host-guest strategy provides a unique approach to developing high-efficiency and stable all-PHSCs processed from green solvents, paving the way for the industrial development of all-PHSCs.
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| 25. |
- Joffrin, E., et al.
(författare)
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Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall
- 2019
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:11
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Forskningsöversikt (refereegranskat)abstract
- For the past several years, the JET scientific programme (Pamela et al 2007 Fusion Eng. Des. 82 590) has been engaged in a multi-campaign effort, including experiments in D, H and T, leading up to 2020 and the first experiments with 50%/50% D-T mixtures since 1997 and the first ever D-T plasmas with the ITER mix of plasma-facing component materials. For this purpose, a concerted physics and technology programme was launched with a view to prepare the D-T campaign (DTE2). This paper addresses the key elements developed by the JET programme directly contributing to the D-T preparation. This intense preparation includes the review of the physics basis for the D-T operational scenarios, including the fusion power predictions through first principle and integrated modelling, and the impact of isotopes in the operation and physics of D-T plasmas (thermal and particle transport, high confinement mode (H-mode) access, Be and W erosion, fuel recovery, etc). This effort also requires improving several aspects of plasma operation for DTE2, such as real time control schemes, heat load control, disruption avoidance and a mitigation system (including the installation of a new shattered pellet injector), novel ion cyclotron resonance heating schemes (such as the three-ions scheme), new diagnostics (neutron camera and spectrometer, active Alfven eigenmode antennas, neutral gauges, radiation hard imaging systems...) and the calibration of the JET neutron diagnostics at 14 MeV for accurate fusion power measurement. The active preparation of JET for the 2020 D-T campaign provides an incomparable source of information and a basis for the future D-T operation of ITER, and it is also foreseen that a large number of key physics issues will be addressed in support of burning plasmas.
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