Grain and stoichiometry engineering for ultra-sensitive perovskite X-ray detectors

Abstract

High sensitivity and a low detection limit are key figures-of-merit for high-energy radiation detectors. Previously, it was found that hot pressing is an effective method to fabricate large, thick compact pellets for highly sensitive X-ray detectors. Herein, we further studied the formation mechanism of a compact pellet and the impacts of the crystal size and stoichiometry of the perovskite pellet on the X-ray detection performance, which has rarely been investigated. It has been found that both heat and pressure are necessary for the formation of a compact pellet and the stoichiometry should be well controlled during the heat treatment. The impacts of temperature are two-fold: facilitating the growth of crystal grains and softening the grains. Pressure will induce the softened grains to form a compact pellet. The crystal grain size will be enlarged with the increase of temperature; however, as the temperature exceeds 150 °C, the atomic ratio of I to Pb will decrease with temperature, which will weaken the X-ray response of the pellet. Furthermore, by adjusting the I to Pb ratio by adding more CH₃NH₃I (MAI), the X-ray response will be improved, achieving a high sensitivity of 4.2 × 10⁵ μC Gy_air⁻¹ cm⁻² at a field of 6.58 V mm⁻¹. These findings provide insights into the use of grain engineering and composition engineering to design effective materials for high-performance X-ray detection.