Enhancing gas-quenching method for fabrication of perovskite-based photovoltaics

The fabrication of gas-quenched perovskite solar cells is analyzed and optimized by using different inert gases. The performance and the stability of the perovskite photovoltaic device are related to the perovskite crystallization properties, such as grain size and grain interspacing distance, as well as its impurity content and defect density. A suitable morphology of a solution-processed perovskite layer can be achieved by different routes. A promising, low cost, and large area compatible way of creating proper crystallization of the perovskite layer is gas quenching. Nitrogen gas is usually used for this purpose to flush the perovskite wet film during coating and control its nucleation stage. It is so far not clear in the literature if there is any relationship between the molecular weight of the quenching gas and the perovskite film morphology. We analyzed the crystallization properties, grain size, surface roughness, and defect density of the perovskite film and the related electrical performance and the stability of the solar cell devices, using nitrogen, helium, and argon as quenching gases. We found that the grain size of the perovskite layer can be tuned by using gases with different molecular weights. Perovskite layers quenched with helium and argon have bigger grain sizes and they are very stable under operational conditions compared to the less stable solar cell device processed by nitrogen gas with a smaller grain size.