Electronic-Ionic Transport in MAPbBr₃ Single Crystal: The Evidence of Super-Linear Power Law in AC Conductivity

Abstract

Hybrid halide perovskites recently emerged as promising semiconductor materials for high-mobility field-effect transistors and detectors due to their unique optoelectronic properties. However, iontronics in these materials play a significant role in charge carrier dynamics. In addition, the impact of grain boundaries and trap density on the dielectric properties and the alternate current (AC) ionic conductivity has been one of the most debated topics. In this work, we have studied the electro-ionic dynamics in perovskite single crystals (SCs) using temperature-dependent impedance spectroscopy and the transient photovoltage (TPV) technique. The device capacitances are temperature-independent, revealing that the temperature is only accelerating the migration of ions (MA+ and Br–) but not increasing the number of ion migrations in single crystals. Moreover, the ions in perovskite single crystals are not trapped at the grain boundaries, and hence all of the ions participate in the conduction; this leads to a higher increase in conductivity resulting in the super-linear power law (SPL) region at a higher frequency. Furthermore, TPV measurements also confirmed the temperature independence recombination lifetime in these materials. The maximum values of responsivity (R), detectivity (D), and external quantum efficiency (EQE) are 12.35 mA/W, 5.89 × 109 Jones, and 38.8%, respectively. This work will be beneficial for understanding charge carrier dynamics in single-crystal field-effect transistors (FETs) and detectors.