Efficiently Improved Photoluminescence in Cesium Lead Halide Perovskite Nanocrystals by Using Bis(trifluoromethane)sulfonimide.

Cesium lead halide perovskite (CsPbX 3 , X = Cl, Br, and I) nanocrystals (NCs) have attracted enormous attention because of their great potential for optoelectronic applications, such as light-emitting diodes (LEDs). However, the photoluminescence and surface ligands of CsPbX 3 NCs have a great impact on their device applications. Herein, we report a molecular superacid of bis(trifluoromethane)sulfonimide (TFSI), which could boost the photoluminescence in the metal halide perovskite nanocrystals. In particular, the photoluminescence quantum yield (PLQY) of CsPbI 3 nanocrystals could be greatly improved from 28.6% to near 100% with the superacid treatment. The improved PLQY in CsPbX 3 nanocrystals is mainly contributed from the surface passivation based on the characterizations. The CsPbX 3 nanocrystals were further modified with PMMA, which could greatly improve their stability while preserving high photoluminescence and good dispersion. The use of superacid combined with a polymer for improving the photoluminescence and stability in CsPbX 3 provides an alternative strategy for optoelectronics.