Organic-inorganic hybrid perovskite as a self-sacrificing template towards high-quality Cs4PbBr6 green emitters

Driven by the urgent need for narrow-band green emitters to address the color gamut deficiency in current white light-emitting diodes (WLEDs), in this work we develop a novel precursor-mediated strategy for the controlled synthesis of high-efficiency Cs 4 PbBr 6 perovskite crystals. Unlike conventional methods that often yield mixed phases, we utilize a judiciously designed organic-inorganic hybrid perovskite crystal, (HDA)Cs 2 Pb 3 Br 10 (HDA = 1,6-hexanediamine), as a self-sacrificing template for the synthsis of high purity Cs 4 PbBr 6 crystals. By precisely adjusting the solvent composition (HBr/DMF(N,N-Dimethylformamide) ratio) during the dissolution-recrystallization process, selective and controllable phase conversion of the hybrid perovskite to Cs 4 PbBr 6 or CsPbBr 3 was achieved. Specifically, the resulting high-quality Cs 4 PbBr 6 crystals exhibit a high photoluminescence quantum yield (PLQY) of up to 94 %. The phase transition mechanism systematically investigated through combined spectroscopic methods unravels that the transformation into all-inorganic perovskites benefits from the stripping of the HDA 2+ organic interlayer by the DMF solvent, while the formation of high-quality Cs 4 PbBr 6 crystals is attributed to the Pb-deficient environment provided by HBr and DMABr (Dimethylammonium bromide). Furthermore, a prototype WLED device fabricated with the obtained Cs 4 PbBr 6 crystals and commercial K 2 SiF 6 :Mn 4+ phosphor demonstrated a high luminous efficiency of 98.04 lm/W and an extensive color gamut covering 136 % of National Television System Committee (NTSC) and 101.6 % of Rec.2020 (derived from the photoluminescence spectra after passing RGB optical filters). These results highlight the potential of the Cs 4 PbBr 6 crystals for application in advanced wide-color-gamut displays.