Ultrastable EVA film-protected Cs4PbBr6 solid powder for wide color gamut backlight display and upconversion emission

In recent years, perovskite nanocrystals (NCs) have been considered novel and potentially valuable optical gain materials that can generate relatively low thresholds and stable stimulated emissions in various external environments. Here, for the first time, an ethylene vinyl acetate copolymer (EVA) film-protected metal halide perovskite (Cs 4 PbBr 6 ) solid powder was successfully synthesized, and its photoluminescence quantum yield (PLQY) value was as high as 61%. In addition, because the Cs 4 PbBr 6 @EVA composite film has excellent optical gain performance, this work explored the optical gain of the Cs 4 PbBr 6 @EVA composite film under 800 nm femtosecond (fs) laser excitation. The experimental results show that the Cs 4 PbBr 6 @EVA composite film has a low threshold (0.89 mJ/cm 2 ) and stable stimulated emission and generates amplified spontaneous emissions (ASEs) at 544 nm. In addition, the application of Cs 4 PbBr 6 @EVA composite film in the field of white light-emitting diodes (WLEDs) has also been studied. The color gamut of this Cs 4 PbBr 6 @EVA composite film is as high as 124.7% of the National Television Standards Committee (NTSC) 1953 standard color gamut and covers 92.8% of the Rec. 2020 standard color gamut. This work proposes a simple method to solve the problem of the poor stability of perovskite solid powder, and the prepared Cs 4 PbBr 6 @EVA composite film shows significant promise in WLED and laser applications.