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The effective detection of X-ray radiation with low threshold is essential to many medical and industrial applications. Three-dimensional (3D) organolead trihalide and double perovskites have been shown to be suitable for direct X-ray detection. However, the sensitivity and stability of 3D perovskite X-ray detectors are limited by ion motion, and there remains a demand to develop green and stable X-ray detectors with high sensitivity and low detection limit. The emerging low-dimensional perovskites have shown promising optoelectronic properties, featuring good intrinsic stability and reduced ion migration. Inspired by this, we show that our 2D layered perovskite-like (NH4)3Bi2I9 device provides unique anisotropic X-ray detecting performance with different crystal directions, effective suppression of ion migration and a low detection limit of 55 nGyair s−1. These results will motivate new strategies to achieve a high-performance X-ray detector by utilizing 2D layered perovskite or perovskite-like materials, without requiring toxic elements. Perovskite-like materials enable different X-ray detection performance along different crystal directions. A low detection limit of 55 nGyair s−1 is demonstrated.

This paper reports the dynamic characteristics of sequential energy transfer up-conversion processes in Yb3+/Er3+:SrMoO4 crystal. A general method based on the emission intensity has been developed to calculate the nonradiative decay rate. A new macroscopic theory has been developed to calculate the energy transfer parameters based on the crystal structure. According to both new calculating methods, the spectral parameters of Yb3+/Er3+:SrMoO4 crystal were calculated, such as up-conversion luminescent quantum efficiencies and threshold pump powers. Both calculating methods may be applied to calculate the spectral parameters of the laser crystal materials.