Understanding interactions between halide perovskite surfaces and atmospheric/VOC gas molecules: an ab initio investigation

Halide perovskite materials have scored great successes in a number of optoelectronic devices such as solar cells. The industrial sector requires an inevitable possibility of contacts between the halide perovskite materials and a number of atmospheric gases and volatile organic compounds (VOCs), which could strongly influence the stability and charge transfer properties of perovskite-based optoelectronic devices. Understanding the interactions between various gas molecules and the perovskite layer could thus be of utmost importance to further optimize perovskite solar cells from an industrial perspective. Surprisingly, a systematic study of the interactions between gas molecules highlighting atmospheric and VOCs and the prototypical CH3NH3PbI3 surfaces is unavailable at the moment. Aiming to bridge the gap, we perform first principles and molecular dynamic calculations to investigate the interactions between CH3NH3PbI3 surfaces and gas molecules, employing CO, CO2, H-2, H2S, NH3, NO, NO2, O-2, and SO2 gas molecules as the adsorbates. Our study suggests that the NH3 gas molecules exhibit detrimental effects on the structural and optical properties of the perovskite material; consequently, halide perovskite solar cells should be strongly protected against these gases. However, the influences of gas molecules on the perovskite layer is not always undesirable, since NH3 molecules can strongly adsorb onto the perovskite surface, increasing the conductivity and initiating optical bleaching in the perovskite underlayer, leading to the viability of the halide perovskite materials as an effective gas sensor. The structure-property relationships of the molecule/perovskite systems investigated in this study could initiate the design protocol of halide perovskite materials toward different applications. This study provides a foundation for the convergence to a fundamental understanding of designing different halide perovskite-based optoelectronic devices.