All-inorganic perovskites have been considered next-generation color converters in the backlit due to their shining optical properties. However, structural instability severely limits their pragmatic applications. Here, CsPbBr 3 /Cs 4 PbBr 6 microcrystals (MCs) were successfully embedded in polydimethylsiloxane (PDMS) films by a facile two-step method. As-prepared PDMS films containing CsPbBr 3 /Cs 4 PbBr 6 MCs (CsPbBr 3 /Cs 4 PbBr 6 @PDMS) obtain high brightness and excellent stability. Meaningfully, the PDMS films not only serve as a double protective matrix that can be used to improve the stability of CsPbBr 3 /Cs 4 PbBr 6 MCs, but also a flexible substrate with high transparency that allows the CsPbBr 3 /Cs 4 PbBr 6 @PDMS films to be used as color conversion materials for backlit displays. To our surprise, when PDMS is coated with CsPbBr 3 /Cs 4 PbBr 6 MCs, the water, thermal and photostability are greatly improved, while the photoluminescence intensity only lost by 10%. Furthermore, by mixing CsPbBr 3 /Cs 4 PbBr 6 MCs with K 2 SiF 6 :Mn 4+ phosphors in PDMS, a monolithic film with high performance was obtained. Its color gamut can reach 127% of the NTSC 1953 standard and 95% of the REC. 2020 standard, exhibiting the bright prospects in the backlit display field.
Qi Wang,Wenzhi Wu,Ruirui Wu,Sen Yang,Yunxia Wang,Jixiang Wang,Zhijun Chai,Qiuju Han
Here, Cs 4 PbBr 6 microcrystals (MCs) are synthesized using a two-phase liquid-liquid immiscible method. In order to unravel the bright green photoluminescence (PL) mechanism for in-situ Cs 4 PbBr 6 MCs, the thermal stability of PL spectra for the supernatant and precipitate of reactants is investigated comparatively. Exciton binding energy, exciton-phonon (EP) coefficient and PL lifetime all indicate that the PL of the precipitate has similar temperature dependence as that of the supernatant. It is found that, according to its structural and optical characteristics , the supernatant of the reactants is CsPbBr 3 nanocrystals (NCs). We also find that the bright green PL from the precipitate of the reactants is due to CsPbBr 3 NCs embedded into Cs 4 PbBr 6 MCs. Experimental results further reveal the size of CsPbBr 3 NCs embedded into Cs 4 PbBr 6 MCs is larger than that of CsPbBr 3 NCs in the supernatant. The surface passivation of the composites can thus help to suppress the thermal quenching of PL for CsPbBr 3 NCs, which opens a new avenue for enhancing the thermal stability of PL for perovskite NCs.
Tao Song,Bo Ma,Hao Wang,Xiao-Dong Zhang,Min Zhao,Pei-Zhu Zheng,Fei Gao,Qiang Wang,Hao-Li Zhang
One ancient recipe to produce rocky candies has found new applications in synthesizing Cs 4 PbBr 6 microcrystals, one 0D perovskite with [PbBr 6 ] 4− octahedra isolated by Cs + bridges that enable quantum confinement and high exciton binding energy favorable for photoluminescence (PL). Herein, various threads are used as seeds to grow perovskites microcrystals, in a way similar to rocky candy production recorded in ancient Chinese recipes. The Cs 4 PbBr 6 growth is an exothermic enthalpy driving process, with the surface energy differentiation determining the formation of rhombohedra shape. The synthesized Cs 4 PbBr 6 microcrystals show a large PL quantum yield (PLQY) of 31.5% and are used to fabricate white and green light-emitting diodes with high performance. Learning from history, this work provides one controllable and generally applicable avenue of fabricating high-quality perovskite crystals with promising applications in photonic and optoelectronic devices, and the elucidation of the growth mechanism offers useful guidance for critical factors directing crystal fabrications in future work.
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