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

• Published in: ACS Physical Chemistry Au Vol. 3; no. 4; pp. 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: Journal Article
• Language: English
• Published: American Chemical Society 26.07.2023
• Subjects: Condensed Matter; Materials Science; Physics; X-ray detectors; ion diffusion; ion migration; sensitivity; metal halide perovskites
• DOI: 10.1021/acsphyschemau.3c00002
• ISSN: 2694-2445

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 (MAPbBr3) 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.