Spectroscopic Insight into Customized Iodine Ligands Passivated Red‐Emitting CsPb(Br,I)3 Perovskite Nanocrystals via Time‐Resolved Photoluminescence

Abstract Molecular engineering toward the structure of a passivation ligand is essential to improve the photoluminescence (PL) efficiency of perovskite nanocrystals (PNCs). To establish the surface recovery mechanism of red‐emitting CsPb(Br,I) 3 NCs with PbI 2 additives in the presence of a tightly bound passivation layer, time‐resolved photoluminescence (TRPL) measurements and their chemometric analysis are employed. Two quaternary alkylammonium ligands, didodecyldimethylammonium iodide (DDAI) and tridodecylmethylammonium iodide (TDAI), are used to form a passivation layer, and then their role in the surface defects recovery is investigated by varying the amount of PbI 2 additives. It is found that the structural difference between DDAI and TDAI can affect the accessibility of PbI 2 additives to surface defects. The TRPL spectra analysis reveals that the ligand passivation with DDAI does not induce discernible lifetime enhancement with using PbI 2 additives, but only a non‐radiative pathway is gradually accelerated with increasing the amount of them. The TDAI ligand, however, shows the opposite behavior to give the best PL performance with a distinct molar ratio of TDAI:PbI 2 , even though the passivation itself gives a lower PL performance. It is argued that the intrinsic structural properties of the TDAI ligand are responsible for the effective surface recovery with the additives.