| 1. |
- Guo, Yuwei, et al.
(författare)
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Phenylalkylammonium passivation enables perovskite light emitting diodes with record high-radiance operational lifetime: the chain length matters
- 2021
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Ingår i: Nature Communications. - : Nature Research. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Perovskite light emitting diodes suffer from poor operational stability, exhibiting a rapid decay of external quantum efficiency within minutes to hours after turn-on. To address this issue, we explore surface treatment of perovskite films with phenylalkylammonium iodide molecules of varying alkyl chain lengths. Combining experimental characterization and theoretical modelling, we show that these molecules stabilize the perovskite through suppression of iodide ion migration. The stabilization effect is enhanced with increasing chain length due to the stronger binding of the molecules with the perovskite surface, as well as the increased steric hindrance to reconfiguration for accommodating ion migration. The passivation also reduces the surface defects, resulting in a high radiance and delayed roll-off of external quantum efficiency. Using the optimized passivation molecule, phenylpropylammonium iodide, we achieve devices with an efficiency of 17.5%, a radiance of 1282.8 W sr(-1) m(-2) and a record T-50 half-lifetime of 130h under 100mAcm(-2). Perovskite light emitting diodes suffer from operational stability, showing rapid decay of performance within minutes to hours after turn-on. Here, the authors investigate how the steric and Coulomb interaction of ammonium passivation molecules with varying alkyl chain length can improve device stability by suppressing iodide ion migration.
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| 2. |
- Ji, Fuxiang, et al.
(författare)
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Lead-Free Halide Double Perovskite Cs2AgBiBr6 with Decreased Band Gap
- 2020
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Ingår i: Angewandte Chemie International Edition. - : Wiley-VCH Verlag. - 1433-7851 .- 1521-3773. ; 59:35, s. 15191-15194
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Tidskriftsartikel (refereegranskat)abstract
- Environmentally friendly halide double perovskites with improved stability are regarded as a promising alternative to lead halide perovskites. The benchmark double perovskite, Cs2AgBiBr6, shows attractive optical and electronic features, making it promising for high-efficiency optoelectronic devices. However, the large band gap limits its further applications, especially for photovoltaics. Herein, we develop a novel crystal-engineering strategy to significantly decrease the band gap by approximately 0.26 eV, reaching the smallest reported band gap of 1.72 eV for Cs2AgBiBr6 under ambient conditions. The band-gap narrowing is confirmed by both absorption and photoluminescence measurements. Our first-principles calculations indicate that enhanced Ag/Bi disorder has a large impact on the band structure and decreases the band gap, providing a possible explanation of the observed band-gap narrowing effect. This work provides new insights for achieving lead-free double perovskites with suitable band gaps for optoelectronic applications.
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| 3. |
- Ji, Fuxiang, et al.
(författare)
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Near-Infrared Light-Responsive Cu-Doped Cs2AgBiBr6
- 2020
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Ingår i: Advanced Functional Materials. - : WILEY-V C H VERLAG GMBH. - 1616-301X .- 1616-3028. ; 30:51
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Tidskriftsartikel (refereegranskat)abstract
- Lead-free halide double perovskites (A(2)B(I)B(III)X(6)) with attractive optical and electronic features are considered to be a promising candidate to overcome the toxicity and stability issues of lead halide perovskites (APbX(3)). However, their poor absorption profiles limit device performance. Here the absorption band edge of Cs(2)AgBiBr(6)double perovskite to the near-infrared range is significantly broadened by developing doped double perovskites, Cs-2(Ag:Cu)BiBr6. The partial replacement of Ag ions by Cu ions in the crystal lattice is confirmed by the X-ray photoelectron spectroscopy (XPS) and solid-state nuclear magnetic resonance (ssNMR) measurements. Cu doping barely affects the bandgap of Cs2AgBiBr6; instead it introduces subbandgap states with strong absorption to the near-infrared range. More interestingly, the near-infrared absorption can generate band carriers upon excitation, as indicated by the photoconductivity measurement. This work sheds new light on the absorption modulation of halide double perovskites for future efficient optoelectronic devices.
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| 4. |
- Kuang, Chaoyang, et al.
(författare)
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Critical role of additive-induced molecular interaction on the operational stability of perovskite light-emitting diodes
- 2021
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Ingår i: Joule. - : Cell Press. - 2542-4351. ; 5:3, s. 618-630
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Tidskriftsartikel (refereegranskat)abstract
- Despite rapid improvements in efficiency and brightness of perovskite light-emitting diodes (PeLEDs), the poor operational stability remains a critical challenge hindering their practical applications. Here, we demonstrate greatly improved operational stability of high-efficiency PeLEDs, enabled by incorporating dicarboxylic acids into the precursor for perovskite depositions. We reveal that the dicarboxylic acids efficiently eliminate reactive organic ingredients in perovskite emissive layers through an in situ amidation process, which is catalyzed by the alkaline zinc oxide substrate. The formed stable amides prohibit detrimental reactions between the perovskites and the charge injection layer underneath, stabilizing the perovskites and the interfacial contacts and ensuring the excellent operational stability of the resulting PeLEDs. Through rationally optimizing the amidation reaction in the perovskite emissive layers, we achieve efficient PeLEDs with a peak external quantum efficiency of 18.6% and a long half-life time of 682 h at 20 mA cm(-2), presenting an important breakthrough in PeLEDs.
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| 5. |
- Luo, Xiyu, et al.
(författare)
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Effects of local compositional heterogeneity in mixed halide perovskites on blue electroluminescence
- 2024
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Ingår i: Matter. - 2590-2393. ; 7:3, s. 1054-1070
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Tidskriftsartikel (refereegranskat)abstract
- Compositional heterogeneity is commonly observed in mixed bromide/iodide perovskite photoabsorbers, typically with minimal effects on charge carrier recombination and photovoltaic performance. Consistently, it has so far received very limited attention in bromide/chloride-mixed perovskites, which hold particular significance for blue light-emitting diodes. Here, we uncover that even a minor degree of localized halide heterogeneity leads to severe non-radiative losses in mixed bromide/chloride blue perovskite emitters, presenting a stark contrast to general observations in photovoltaics. We not only provide a visualization of the heterogeneity landscape spanning from micro-to sub-microscale but also identify that this issue mainly arises from the initially formed chloride-rich clusters during perovskite nucleation. Our work sheds light on a long-term neglected factor impeding the advancement of blue light-emitting diodes using mixed halide perovskites and provides a practical strategy to mitigate this issue.
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| 6. |
- 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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| 7. |
- Teng, Pengpeng, et al.
(författare)
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Degradation and self-repairing in perovskite light-emitting diodes
- 2021
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Ingår i: Matter. - : Elsevier. - 2590-2393 .- 2590-2385. ; 4:11, s. 3710-3724
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Tidskriftsartikel (refereegranskat)abstract
- One of the most critical challenges in perovskite light-emitting diodes (PeLEDs) lies in poor operational stability. Although field dependent ion migration is believed to play an important role in the operation of perovskite optoelectronic devices, a complete understanding of how it affects the stability of PeLEDs is still missing. Here, we report a unique self-repairing behavior that the electroluminescence of moderately degraded PeLEDs can almost completely restore to their initial performance after resting. We find that the accumulated halides within the hole transport layer undergo back diffusion toward the surface of the perovskite layer during resting, repairing the vacancies and thus resulting in electroluminescence recovery. These findings indicate that one of the dominant degradation pathways in PeLEDs is the generation of halide vacancies at perovskite/hole transport layer interface during operation. We thus further passivate this key interface, which results in a high external quantum efficiency of 22.8% and obviously improved operational stability.
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| 8. |
- Yu, Hongling, et al.
(författare)
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Color-Stable Blue Light-Emitting Diodes Enabled by Effective Passivation of Mixed Halide Perovskites
- 2021
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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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| 9. |
- Yu, Hongling, 1987-, et al.
(författare)
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Single-emissive-layer all-perovskite white light-emitting diodes employing segregated mixed halide perovskite crystals
- 2020
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Ingår i: Chemical Science. - : Royal Society of Chemistry. - 2041-6520 .- 2041-6539. ; 11:41, s. 11338-11343
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Tidskriftsartikel (refereegranskat)abstract
- Metal halide perovskites have demonstrated impressive properties for achieving efficient monochromatic light-emitting diodes. However, the development of white perovskite light-emitting diodes (PeLEDs) remains a big challenge. Here, we demonstrate a single-emissive-layer all-perovskite white PeLED using a mixed halide perovskite film as the emissive layer. The perovskite film consists of separated mixed halide perovskite phases with blue and red emissions, which are beneficial for suppressing halide anion exchange and preventing charge transfer. As a result, the white PeLED shows balanced white light emission with Commission Internationale de L'Eclairage coordinates of (0.33, 0.33). In addition, we find that the achievement of white light emission from mixed halide perovskites strongly depends on effective modulation of the halide salt precursors, especially lead bromide and benzamidine hydrochloride in our case. Our work provides very useful guidelines for realizing single-emissive-layer all-perovskite white PeLEDs based on mixed halide perovskites, which will spur the development of high-performance white PeLEDs.
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| 10. |
- Zhang, Jibin, et al.
(författare)
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Highly Luminescent and Stable CsPbI3 Perovskite Nanocrystals with Sodium Dodecyl Sulfate Ligand Passivation for Red-Light-Emitting Diodes
- 2021
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Ingår i: The Journal of Physical Chemistry Letters. - : AMER CHEMICAL SOC. - 1948-7185. ; 12:9, s. 2437-2443
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Tidskriftsartikel (refereegranskat)abstract
- CsPbI3 perovskite nanocrystals (NCs) have recently emerged as promising materials for optoelectronic devices because of their superior properties. However, the poor stability of the CsPbI3 NCs induced by easy ligand desorption represents a key issue limiting their practical applications. Herein, we report stable and highly luminescent black-phase CsPbI3 NCs passivated by novel ligands of sodium dodecyl sulfate (SDS). Theoretical calculation results reveal a stronger adsorption energy of SDS molecules at the CsPbI3 surface than that of commonly used oleic acid. As a result, the defect formation caused by the ligand loss during the purification process is greatly suppressed. The optimized SDS- CsPbI3 NCs exhibit significantly reduced surface defects, much enhanced stability, and superior photoluminescence efficiency. The red perovskite light-emitting diodes based on the SDS-CsPbI3 NCs demonstrate an external quantum efficiency of 8.4%, which shows a 4-fold improvement compared to the devices based on the oleic acid-modified CsPbI3 NCs.
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| 11. |
- Zhang, Jibin, et al.
(författare)
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Ligand-Induced Cation-p Interactions Enable High-Efficiency, Bright, and Spectrally Stable Rec. 2020 Pure-Red Perovskite Light-Emitting Diodes
- 2023
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095.
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Tidskriftsartikel (refereegranskat)abstract
- Achieving high-performance perovskite light-emitting diodes (PeLEDs) with pure-red electroluminescence for practical applications remains a critical challenge because of the problematic luminescence property and spectral instability of existing emitters. Herein, high-efficiency Rec. 2020 pure-red PeLEDs, simultaneously exhibiting exceptional brightness and spectral stability, based on CsPb(Br/I)(3) perovskite nanocrystals (NCs) capping with aromatic amino acid ligands featuring cation-pi interactions, are reported. It is proven that strong cation-pi interactions between the PbI6-octahedra of perovskite units and the electron-rich indole ring of tryptophan (TRP) molecules not only chemically polish the imperfect surface sites, but also markedly increase the binding affinity of the ligand molecules, leading to high photoluminescence quantum yields and greatly enhanced spectral stability of the CsPb(Br/I)(3) NCs. Moreover, the incorporation of small-size aromatic TRP ligands ensures superior charge-transport properties of the assembled emissive layers. The resultant devices emitting at around 635 nm demonstrate a champion external quantum efficiency of 22.8%, a max luminance of 12 910 cd m(-2), and outstanding spectral stability, representing one of the best-performing Rec. 2020 pure-red PeLEDs achieved so far.
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| 12. |
- Zhao, Haifeng, et al.
(författare)
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High-Brightness Perovskite Light-Emitting Diodes Based on FAPbBr(3) Nanocrystals with Rationally Designed Aromatic Ligands
- 2021
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Ingår i: ACS Energy Letters. - : AMER CHEMICAL SOC. - 2380-8195. ; 6:7, s. 2395-2403
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Tidskriftsartikel (refereegranskat)abstract
- Despite rapid developments of light-emitting diodes (LEDs) based on emerging perovskite nanocrystals (PeNCs), it remains challenging to achieve devices with integrated high efficiencies and high brightness because of the insulating long-chain ligands used for the PeNCs. Herein, we develop highly luminescent and stable formamidinium lead bromide PeNCs capped with rationally designed short aromatic ligands of 2-naphthalenesulfonic acid (NSA) for LEDs. Compared with commonly used oleic acid ligands, the NSA molecules not only preserve the surface properties of the PeNCs during the purification but also notably improve the electrical properties of the assembled emissive layers, ensuring efficient charge injection/transport in the devices. The resulting champion LED with electroluminescence approaching the Rec. 2020 green primary color demonstrates a high brightness of 67 115 cd cm(-2) and a peak external quantum efficiency of 19.2%. More impressively, the device shows negligibly decreased efficiency at an elevated brightness of 20 000 cd cm(-2) and a well-retained efficiency of over 10% at around 65 000 cd cm(-2), presenting a breakthrough in LEDs based on PeNCs.
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