Exciton and Charge Transport in Halide Perovskites

The movement of excitons – bound electron-hole pairs – and free charge carriers in semiconductors is central to the operation of optoelectronic devices. Recently, time-resolved optical microscopy has emerged as a powerful experimental technique for studying the spatiotemporal dynamics of charges and excitons in emerging semiconductor materials under a variety of experimental conditions. In this talk, I will present recent progress using time-resolved photoluminescence microscopy to understand charge and exciton transport in halide perovskite materials. I will introduce the technique and its history, review successes and failures, and efforts to benchmark time-resolved microscopy data against other techniques (e.g. Hall effect, FET mobility). Finally, I will present our findings in halide perovskites, including 1) temperature-dependent transition between free carrier and exciton-dominated transport in bulk halide perovskite crystals, 2) effect of A-site cation and grain boundaries, 3) anomalous exciton transport phenomena at cryogenic temperature, and 4) exciton transport in perovskite nanocrystal solids and nanocrystal superlattices.