Carrier Transport Limited by Trap State in Cs₂AgBiBr₆ Double Perovskites

Understanding the photoinduced carrier dynamics in Cs₂AgBiBr₆ double perovskites is essential for their application in optoelectronic devices. Herein, we report an investigation on the temperature-dependent carrier dynamics in a Cs₂AgBiBr₆ single crystal (SC). The time-resolved photoluminescence (TRPL) measurement indicates that the majority of carriers (>99%) decay through a fast trapping process at room temperature, and as the temperature decreases to 123 K, the population of carriers with a slow fundamental decay kinetics rises to ∼50%. We show that the carrier diffusion coefficient (theoretical diffusion length) varies from 0.020 ± 0.003 cm² s^-1 (0.70 μm) at 298 K to 0.11 ± 0.010 cm² s^-1 (2.44 μm) at 123 K. However, in spite of the long diffusion length, the population of carriers that can perform long-distance transport is restricted by the trap state, which is likely a key reason limiting the performance of Cs₂AgBiBr₆ optoelectronic devices.