Alam Aftab, Aslam M
Department of Physics, Indian Institute of Technology Bombay, Mumbai, India.
J Chem Phys. 2023 Aug 28;159(8). doi: 10.1063/5.0154047.
In this work, we studied the impact of environmental constituents such as oxygen (O2) and moisture on halide double perovskite (HDP) films. The transport measurements indicate that an increment in O2 concentration enhances the resistivity of a Cs2AgBiBr6 film by two orders of magnitude. The adsorption of O2 on the film's surface helps in passivation of defects (∼50% reduction in defect density on O2 exposure), which inhibits ion migration and results in an increased resistivity of the film. The process of adsorption and desorption of O2 on the film surface is found to be fully reversible. In contrast, the resistivity of double perovskite films decreases by an order of magnitude in the presence of moisture. This is attributed to the generation of free protons as a result of the dissociation of water molecules at the films' surface, hence exhibiting an increase in current under external bias. The HDP films possess high resistivity (for T < 100 °C) due to the desorption of physisorbed water layers from the surface, which gradually decreases with an increase in the operating temperature. This work demonstrates that O2 and moisture are a good combination for defect passivation in any HDPs, in general.
在这项工作中，我们研究了诸如氧气（O₂）和水分等环境成分对卤化物双钙钛矿（HDP）薄膜的影响。输运测量表明，O₂浓度的增加会使Cs₂AgBiBr₆薄膜的电阻率提高两个数量级。O₂在薄膜表面的吸附有助于缺陷钝化（暴露于O₂时缺陷密度降低约50%），这抑制了离子迁移并导致薄膜电阻率增加。发现O₂在薄膜表面的吸附和解吸过程是完全可逆的。相比之下，在有水分的情况下，双钙钛矿薄膜的电阻率降低一个数量级。这归因于薄膜表面水分子解离产生自由质子，因此在外部偏压下电流增加。由于表面物理吸附水层的解吸，HDP薄膜具有高电阻率（对于T < 100 °C），其随着工作温度的升高而逐渐降低。总体而言，这项工作表明O₂和水分是任何HDP中缺陷钝化的良好组合。
