Stability of Cesium-Based Lead Halide Perovskites under UV Radiation.

Lead halide perovskites have been extensively studied for their potential applications, including photodetectors, solar cells, and high-energy radiation detection. These applications are possible because of their unique optoelectronic properties, such as tunable band gap, high optical absorption coefficient, and unique defect self-healing properties, which result in high defect tolerance. Despite these advantages, the long-term stability remains a critical issue that could hinder commercial applications of these materials. Reports on the stability of lead halide perovskites for optoelectronic applications have normally focused on methylammonium (MA)/formamidinium (FA), with very limited information for other systems, in particular, Cs-containing perovskites. In this paper, we report the stability of thick CsPbBr3-x Cl x polycrystalline thin films (∼8 µm) with several halide Br-Cl ratios after exposure to deep UV radiation. The chemical, crystal structure, optical, and electrical properties are analyzed, and the results are used to propose a degradation mechanism. The chemical analysis on the surface and bulk of the films indicates the formation of cesium oxide after UV exposure, with no significant change in the crystalline structure. The proposed mechanism explains the formation of cesium oxides during UV exposure. The I-V characteristics of diode structures also showed significant degradation after UV exposure, primarily at lower diode rectification ratios. The mechanism proposed in this paper can contribute to developing strategies to enhance the long-term stability of inorganic lead halide perovskites under UV exposure.

Solid-State Neutron Detection Based on Methylammonium Lead Bromide Perovskite Single Crystals.

Perovskite-based semiconductors, such as methylammonium and cesium lead halides (MPbX3: M = CH3NH3+ or Cs+; X = I-, Br-, or Cl-), have attracted immense attention for several applications, including radiation detection, due to their excellent electronic and optical properties.1,2,3,4,5,6 In addition, the combination of perovskites with other materials enables unique device structures. For example, robust and reliable diodes result when combined with metal oxide semiconductors. This device can be used for detection of nonionizing and ionizing radiation. In this paper, we report a unique perovskite single-crystal-based neutron detector using a heterojunction diode based on single-crystal MAPbBr3 and gallium oxide (Ga2O3) thin film. The MAPbBr3/Ga2O3 diodes demonstrate a leakage current of ∼7 × 10-10 A/mm2, an on/off ratio of ∼102, an ideality factor of 1.41, and minimal hysteresis that enables alpha particle, gamma-ray, and neutron detection at a bias as low as (-5 V). Gamma discrimination is further improved by 85% by optimizing the thickness of the perovskite single crystal. The MAPbBr3/Ga2O3 diodes also demonstrate a neutron detection efficiency of ∼3.92% when combined with a 10B neutron conversion layer.