Improving the Stability of Lead-Free CsSnBr₃ Halide Perovskite by DDAB-Assisted Postpassivation Surface Engineering

Lead-based halide perovskites (HPs) have become a center of attention in the field of optoelectronics; however, the toxic nature of lead is a bottleneck in their long-term commercial exploration. The Sn-based HPs are being considered as potential substitutes; however, their poor stability under ambient conditions is a major challenge. To address this, we have attempted postpassivation of CsSnBr₃ with didodecyldimethylammonium (DDAB), a biexchange ligand. This ligand replaces the weak surface capping of OAm with DDA⁺ and also fills the halide (Br) vacancies on the HP surface, thereby increasing the stability of the lead-free CsSnBr₃ HPs. In addition to improved stability, the DDAB-functionalized CsSnBr₃ HPs show ∼5.5 times enhancement in the PL intensity. The DDAB-functionalized CsSnBr₃ HPs with shorter chain lengths of DDAB (which might result in improved carrier current), prolonged stability, and improved PL behavior could be a better choice for optoelectronic applications.