High Curvature PEDOT:PSS Transport Layer Toward Enhanced Perovskite Light-Emitting Diodes.

The rapidly developed metal halide perovskite light-emitting diodes (PeLEDs) are considered as a promising candidate for next-generation display and illumination, but the unbalanced charge transport is still a hard-treat case to restrict its efficiency and operational stability. Here, a high curvature PEDOT:PSS transport layer is demonstrated via the self-assembly island-like structures by the incorporation of alkali metal salts. Benefiting from the dielectric confinement effect of the high curvature surface, the modified CsPbBr3 -based PeLEDs present a 2.1 times peak external quantum efficiency (EQE) from 6.75% to 14.23% and a 3.3 times half lifetime (T50 ) from 3.96 to 13.01 h. Besides, the PeLEDs show high luminance up to 44834 cd m-2 . Evidently, this work may provide a deep insight into the structure-activity relationship between the micro-structures at the PEDOT:PSS/perovskite interface and the performance of PeLEDs, and crack the codes for ameliorating the performance of PeLEDs via interfacial micro-structured regulation.

Unraveling the role of hydrogen bromide in the growth of cesium lead bromide perovskite nanocrystals.

Hydrogen bromide (HBr) could substantially improve the quality of cesium lead bromide perovskite (CsPbBr3) nanocrystals (NCs) and greatly enhance their optoelectronic performance. However, clarifying the role of HBr in the growth of CsPbBr3 NCs has been a substantial challenge thus far. Herein, we design an in situ cryogenic photoluminescence system using liquid nitrogen to unravel the role played by HBr in the growth of CsPbBr3 NCs. Compared with no HBr (∼40 s), HBr improves the nucleation rate of CsPbBr3 NCs about two times (∼20 s), and its emission peak also exhibits a redshift of âˆ¼30 nm. Thus, we conclude that HBr accelerates the nucleation rate of CsPbBr3 NCs and extends their growth stage, affording the generation of large grains. Perovskite light-emitting diodes based on CsPbBr3 NCs with added HBr also exhibit an outstanding performance. These outcomes provide new insights into the role of HBr in CsPbBr3 NCs and help prepare high-quality CsPbBr3 NCs for use in the fabrication of efficient CsPbBr3 NC-based optoelectronic devices.

Structurally Tolerance-Factor-Tuned Metal Halide Nanocrystals for Environmentally Stable and Efficient Red Light-Emitting Diodes.

Black phase CsPbI3, naturally possessing the superiority of high radiative recombination efficiency and narrow emission line width, shows promise for commercial applications of red perovskite light-emitting diodes (PeLEDs). However, the metastable black phase CsPbI3 with a marginal tolerance factor (t) of 0.81 would easily convert to the nonoptical yellow phase. Herein, we demonstrate the strategy of partial substitution of larger dimethylammonium cation (DMA+) for Cs+ to achieve the stable tolerance factor of 0.903 for greatly improved Cs0.7DMA0.3PbI3 nanocrystals. These NCs present a superior ultraviolet (UV) irradiation stability by retaining 80% of the initial photoluminescence intensity after 5 h, which is much better than that of its counterparts (retaining 30%). Based on this, the as-developed red PeLEDs demonstrate remarkable luminance of 1258 cd/m2 and external quantum efficiency of 3.39%, which are almost 6 times and 3 times that of its counterparts, respectively (203 cd/m2 and 1.28%). This strategy may pave the way to improving the stability and efficiency of PeLEDs.

The metal doping strategy in all inorganic lead halide perovskites: synthesis, physicochemical properties, and optoelectronic applications.

All inorganic perovskites CsPbX3 (X = Cl, Br, I), rising stars of optical materials, have shown promising application prospects in optoelectronic and photovoltaic fields. However, some open issues still exist in these perovskites, like poor long-term stability, inevitable intrinsic defects and much nonradiative recombination, which greatly weakens their optical capability and seriously hinders their further development. The metal doping strategy, through the partial substitution of foreign ions for native ions, has gradually become an effective method for significantly enhancing the comprehensive properties of CsPbX3. Whereas some previous studies have reported the impressive properties of metal-doped CsPbX3, there is still a lack of a comprehensive review on the influences of metal doping on CsPbX3. In this review, we aim to provide a systematic review of the latest achievements in metal-doped CsPbX3, which focuses on their synthetic methods and the positive effects of metal doping on structure, optical properties, morphology control, carrier behavior and related optoelectronic and photovoltaic devices. Finally, we put forward a few opportunities and challenges about the further investigation of metal-doped perovskites, which may help researchers explore new research directions.

Thermodynamics-Induced Injection Enhanced Deep-Blue Perovskite Quantum Dot LEDs.

Precisely tuning emission spectra through the component control of mixed halides has been proved to be an efficient method for procuring deep-blue perovskite LEDs (PeLEDs). However, the inferior color instability and lifetime attenuation, originated from vacancy- and trap-mediated mechanisms under an external field, remain an uninterruptedly formidable challenge for the commercial development of PeLEDs. Here, an ultrafast thermodynamics-induced injection enhancement strategy was employed to promote efficient carrier recombination within perovskite quantum dots (QDs), accompanied by less inefficient charge accumulation and trap generation, enabling deep-blue PeLEDs with improved thermal and spectral stability. The resultant PeLEDs feature an external quantum efficiency (EQE) of 3.66%, a max luminance of 2100 cd/m2 at the electroluminescence (EL) of 460 nm, and a halftime of 288 s. This work provides a general platform for promoting the EL performances and a deep insight into unraveling the degradation mechanism of blue PeLEDs.