Ultrafast Excited-State Transport and Decay Dynamics in Cesium Lead Mixed Halide Perovskites

While significant research efforts directed toward characterizing the excited-state dynamics of lead halide perovskites have enabled promising advances in photovoltaic, light-emitting diode, and laser technologies, a detailed correlation between composition and functionality in this promising class of materials remains unestablished. We use pump–probe microscopy to characterize both transport and relaxation dynamics in individual crystals of CsPbI 2 Br, a mixed halide, all-inorganic analogue to the well-studied organic–inorganic hybrid perovskites. In contrast to the methylammonium lead tri-iodide perovskite, we find excited-state dynamics that decay primarily via first-order and Auger mechanisms. By global fitting of power-dependent kinetics collected from individual domains, we find a range of Auger rate constants between 3.3 × 10 –30 and 1.5 × 10 –28 cm 6 /s, with negligible contributions from second-order (bimolecular) processes. Direct imaging of the excited-state spatial evolution reveals an average diffusion constant of 0.27 cm 2 /s, a value that is nearly an order of magnitude smaller than that of single-crystal, organic–inorganic analogues.