Ionic Field Screening in MAPbBr 3 Crystals Revealed from Remnant Sensitivity in X-ray Detection

• Published in: ACS Physical Chemistry Au 2023-07, Vol.3 (4), p.386-393
• Main Authors: Alvarez, Agustin O, Lédée, Ferdinand, García-Batlle, Marisé, López-Varo, Pilar, Gros-Daillon, Eric, Guillén, Javier Mayén, Verilhac, Jean-Marie, Lemercier, Thibault, Zaccaro, Julien, Marsal, Lluis F, Garcia-Belmonte, Germà, Almora, Osbel
• Format: Article
• Language: English
• ISSN: 2694-2445; 2694-2445
• DOI: 10.1021/acsphyschemau.3c00002

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 ) 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 ( = 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.