Enhancement of photostability in perovskite nanocrystals and mechanism elucidation via fine structural design of the adsorption head group in zwitterionic ligand

Abstract

Perovskite nanocrystals (PeNCs) are regarded as promising next-generation photoluminescent materials for displays. However, it has been suffering from significant stability issues, particularly under photoirradiation. Previous studies have reported that zwitterionic ligands can enhance photostability via a chelate effect derived from specific substituents. However, the mechanism by which zwitterionic ligands improve photostability remains unclear.

Therefore, we investigated the substituent spacing in zwitterionic ligands to elucidate how they improve the photostability of PeNCs. We found that the key factor is the proportion of zwitterionic ligands on the PeNC surface, acted by the chelate effect. SB3, the ligand bearing three carbon atoms between its substituents, achieved 87.4% surface coverage- significantly higher than that of ligands with other substituent spacings. Consequently, this high coverage critically enhanced the photostability, enabling PeNCs@SB3 to maintain their photoluminescence quantum yield (PLQY) for 30 hours under photoirradiation. We propose a novel perspective on ligand engineering strategies that focuses on the ligand proportions on the surface of PeNCs to improve their photostability.