Synthesizing Bright CsPbBr3 Perovskite Nanocrystals with High Purification Yields and Their Composites with In Situ-Polymerized Styrene for Light-Emitting Diode Applications

The room-temperature ligand-assisted reprecipitation (LARP) technique has been established as a facile and large-scale method for synthesizing lead halide perovskite nanocrystals (PNCs). However, it is difficult to purify these PNCs through precipitation/redispersion processes, arising from their fragile crystal structure and low PNC concentration. In this paper, we proposed to apply anisole as the reaction solvent, which has slightly increased polarity relative to the often used toluene. As a result, the as-synthesized CsPbBr3 PNCs can be easily isolated from the crude solution through direct centrifugation without adding antisolvents. The obtained purified CsPbBr3 (OA/OAm-CsPbBr3) PNCs capped with oleic acid (OA) and oleylamine (OAm) had a 50-fold improvement in molar production yields. Meanwhile, they showed a relatively high photoluminescence quantum yield (PLQY) of 64%. This method is also feasible for more fragile red-emitting PNCs. The obtained CsPbBrI2 PNCs with an emission maximum at 629 nm had a PLQY of 65% and a 7-fold improvement in molar production yields. Furthermore, when bromide-rich ligands i.e., cetyltrimethylammonium bromide (CTAB) were used, the PLQY of the purified CsPbBr3 (CTAB-CsPbBr3) PNCs can further increase to around 90%. Subsequently, for facile coating PNCs with polystyrene (PS), a mild polymerization method was established by adopting a low-temperature initiator. The fabricated CTAB-CsPbBr3@PS composite had a higher PLQY (77% vs 21%) and enhanced stability against water and heat, compared to that of the OA/OAm-CsPbBr3@PS composite. Finally, the CTAB-CsPbBr3@PS composite was demonstrated to produce super-wide color gamut (130% NTSC) backlights with a luminous efficacy of 71.1 lm/W.