Temperature and Phase Dependence of Carrier Diffusion in Single Crystal MAPbI₃ Perovskite Microstructures

Understanding and improving carrier transport in photovoltaic materials is crucial to developing high quality solar energy harvesting devices. Here, we have investigated carrier diffusion lengths in single crystal methylammonium lead iodide (MAPbI₃) microstuctures via scanning photocurrent microscopy. Carrier diffusion lengths were found to increase abruptly once below the transition temperature from the tetragonal to the orthorhombic phase and reached 200 ± 50 μm at 80 K. Enormous mobility values of 3 x 10⁴ cm² / V s were extracted at 80 K using these long diffusion lengths in combination with transient photocurrent lifetime measurements. We attributed the increased diffusion lengths to the emergence of an excitonic nature to the transport in the orthorhombic phase. Our findings provide significant fundamental insights on the temperature and phase-dependent charge transport properties of halide perovskites.