Precursor purity effects on solution-based growth of MAPbBr3 single crystals towards efficient radiation sensing

Abstract

Organometallic halide perovskite (OMHPs) single crystals have recently gained attention for high-energy radiation detection due to their low trap state densities, high bulk resistivities, excellent stopping power and cost-effective solution growth. An integral focus for radiation sensing materials is the reduction of trap states to enhance charge transport properties. In this perspective, we investigate the use of high and low purity precursors for growth to understand impurity inclusion, as well as effects on structural properties due to impurities. Using both high purity and low purity precursors, we report minimal effects on impurity inclusion observed via Raman, ToF-SIMS and X-ray diffraction. Through SEM analysis, we observe that the particle size in the grown single crystal increased on average by a factor of two to five, when using high purity precursors. The microstructural changes affect the recombination mechanisms, promoting longer charge carrier lifetimes (τ_avg), where time-resolved photoluminescence shows a large increase from τ_avg = 1.26 × 10⁻⁶ s (low purity) to τ_avg = 1.18 × 10⁻⁴ s (high purity). We further investigate the purity effects with alpha radiation detection, demonstrating charge collection efficiency and observing an increase in charge collection by 32 ± 30% using the higher purity precursors. The microstructural differences in growth are herein proposed to be caused by nucleation from the impurities present in the solution, thereby adversely affecting the electronic properties of the MAPbBr₃ single crystals. In this perspective, we provide a deeper understanding of the effects of precursor purity on solution-based single crystal growth of OMHPs towards development of efficient radiation sensors and optoelectronic devices.