Ozone Gas-Sensing Based on Specular Reflectance Changes in Smoorth, Highly-Reflecting, PVP-Stabilized, All-Inorganic Perovskite Thin Films

When gas molecules adsorb onto the surface of a semiconducting layer of the right bandgap and electrical/chemical properties, such films can provide state-of-the-art performance for detecting gases via changes in electrical conductivity or other optoelectronic properties. Recently, metal-halide perovskite materials, which have been extensively studied for applications in light-harvesting and light-emission, have drawn interest as sensing components due to their ability of exhibit reversable changes in electrical conductivity when exposed to gases like ozone, CH₄, H₂, and others [1]. Numerous studies have demonstrated the use of metal halide perovskites in detecting various air contaminants [2]. Despite this research, the instability and roughness of the films still inhibit the commercialization of perovskite-based sensors. Here, we report the fabrication of thin films of CsPbI_xBr_3-x(x=3,2,1.5,1,0) perovskites for gas-sensing applications that are stable, homogenous, and smooth. To make such films, we used added polyvinylpyrrolidone (PVP) in the precursor solutions. The polymer helps to grow homogeneous films and it stabilizes the photoluminescent phase of CsPbI_xBr_3-x in ambient conditions. We studied the effect of PVP on the structure and vibrational modes using Powder-XRD and Raman. We observed that the resultant films are optically smooth, and strongly reflect light. The as-fabricated thin film of the perovskites shows remarkable sensitivity to ozone. When exposed to ozone, the PVP-stablized perovskite films show a remarkable change in reflection, which is mostly reversable and definitely reusable, depending on the Bromide/Iodide ratio. Future gas sensing devices based on the bright phases of CsPbI_xBr_3-x stabilized with PVP could be made easy and cost-effective with high sensitivity due to their straightforward fabrication procedure.<br/><br/><b>References:</b><br/>1. Chen C, Cai Q, Luo F, Dong N, Guo L, Qiu B, Lin Z, Sensitive Fluorescent Sensor for Hydrogen Sulfide in Rat Brain Microdialysis via CsPbBr₃ Quantum Dots. <i>Anal Chem</i>, (2019); <b>91</b> (24), 15915–15921.<br/>2. Zhu Z, Sun Q, Zhang Q, Dai J, Xing G, Li S, Huang X, Huang W, Metal halide perovskites: stability and sensing-ability. <i>J Mater Chem C Mater</i>. (2018); <b>6</b> (38), 10121–10137.