Revival of Degraded CsPbI 3 Nanocrystals by Diselenide Ligand and Nanocrystal Self-Assembly on Nanofibrilar Ligand Template.

Among the lead halide perovskite (LHP) family, CsPbI 3 is known to be significantly vulnerable to moisture, which hinders its use in real device applications. It is reported that chalcogen-based ligands can better stabilize CsPbI 3 and revive nanocrystals (NCs). Here, diphenyl diselenide (DPhDSe) ligand is used to revive the degraded CsPbI 3 NCs through a post-synthetic treatment of adding a small amount of DPhDSe in the degraded NC dispersion. DPhDSe in the dispersion formed nanofibrillar crystals at a low temperature through the π-π stacking of the phenyl ring. The nanofibrils played as a template on which the NCs self-assembled and they are attached side-by-side to form microfibers. The microfiber powder containing the NCs is optically stable at ambient conditions and morphologically self-healable by mild thermal annealing due to the dynamic Se─Se bond. The mechanism of the structural changes, optical transitions, and chemical changes has been systematically characterized through electron microscopy, diffraction, spectroscopy, and elemental analysis.