Impact of ultrafast carrier cooling on the open-circuit voltage in a Ag/Bi co-doped CsPbBr3 NC based photodetector

Precise control of the hot carrier (HC) relaxation dynamics in halide perovskites is crucial for optimizing the performance of optoelectronic applications requiring efficient energy harvesting and charge transport. Herein, we investigate the effects of Bi, Ag, and Ag/Bi co-doping on HC relaxation in CsPbBr 3 nanocrystals (NCs) using femtosecond transient absorption spectroscopy (TAS) and assess their impact on self-powered photodetectors (PDs). Temperature-dependent photoluminescence (PL) and HC energy loss rate analysis reveal an almost twofold reduction in the coupling strength and a threefold enhancement in the longitudinal optical (LO) phonon lifetimes after doping/co-doping. The extended LO phonon lifetime and suppressed coupling strength after Ag and Ag/Bi co-doping enhance the hot phonon bottleneck effect and prolong the HC relaxation process. These findings and improved self-powered PD performance provide a practical strategy for tailoring the HC dynamics in perovskite NCs, paving the way for designing high-efficiency photodetectors and solar cells.