Ionic Field Screening in MAPbBr3 Crystals Revealed from Remnant Sensitivity in X-ray Detection

Research on metal halide perovskites as absorbers for X-ray detection is an attractive subject due to the optimal optoelectronic properties of these materials for high-sensitivity applications. However, the contact degradation and the long-term instability of the current limit the performance of the devices, in close causality with the dual electronic-ionic conductivity of these perovskites. Herein, millimeter-thick methylammonium-lead bromide (MAPbBr(3)) single and polycrystalline samples are approached by characterizing their long-term dark current and photocurrent under X-ray incidence. It is shown how both the dark current and the sensitivity of the detectors follow similar trends at short-circuit (V = 0 V) after biasing. By performing drift-diffusion numerical simulations, it is revealed how large ionic-related built-in fields not only produce relaxations to equilibrium lasting up to tens of hours but also continue to affect the charge kinetics under homogeneous low photogeneration rates. Furthermore, a method is suggested for estimating the ionic mobility and concentration by analyzing the initial current at short-circuit and the characteristic diffusion times.

Automated summary

Research on metal halide perovskites as absorbers for X-ray detection is important due to their optimal optoelectronic properties. However, the contact degradation and long-term instability of the current limit device performance, which is related to the dual electronic-ionic conductivity of perovskites. The study characterizes the long-term dark current and photocurrent of methylammonium-lead bromide (MAPbBr(3)) samples under X-ray incidence, revealing the influence of large ionic-related built-in fields on charge kinetics and suggesting a method to estimate ionic mobility and concentration.