Role of Inter‐Particle Connectivity in the Photo‐Carrier Cooling Dynamics in Perovskite Quantum Dot Solids

Abstract Intraband carrier relaxation in quantum dots (QDs) has been a subject of extensive spectroscopic investigation for several decades, and have been used to optimize the efficiency of opto‐electronic processes. In the past few years, metal halide perovskites‐based QDs have been shown to exhibit slow hot‐carrier cooling characteristics that are desirable for photo‐energy harvesting technologies. While several mechanisms are proposed to rationalize the retardation of the cooling dynamics, including hot‐phonon bottleneck and polaronic effects, the role of inter‐particle connectivity in these dynamics is largely ignored. Here, an in‐depth study of photo‐excitation dynamics and carrier cooling on perovskite QD solids with varying degrees of inter‐dot coupling is presented. It is observed that inter‐particle connectivity has deterministic effects on the many‐body interactions that are relevant for carrier cooling. These include carrier–carrier interactions that result in Auger‐reheating of the carriers, and lattice characteristics that subsequently affect the phonon‐assisted cooling dynamics. This spectroscopic study of ultrafast carrier dynamics in perovskite QD solids establishes inter‐dot separation as a critical material design parameter for the optimization of photo‐generated carrier temperature, which fundamentally determines the luminescence characteristics and thus the opto‐electronic quality of the material.