Various halide perovskite crystals based on CH₃NH₃PbI₃ (abbreviated MAPbI₃) are expected to become next-generation solar cell materials and are currently undergoing research and development worldwide. However, despite its high photoelectric conversion efficiency, MAPbI₃ has an unstable structure due to the presence of CH₃NH₃ (MA) organic molecules, and the decomposition of CH₃NH₃ from CH₃NH₃PbI₃ in the atmosphere results in the formation of PbI₂. The expensive 2,2',7,7'-tetrakis (N,N-di-p-methoxyphenylamino)-9,9'-spirobifluorene (spiro-OMeTAD) is widely used throughout the world as a hole transport material in perovskite solar cells. To enhance hole transport, spiro-OMeTAD needs dopants such as lithium bis(trifluoromethane sulfonyl) imide and 4-tert-butylpyridine, which are highly hygroscopic and accelerate degradation of the perovskite layer when moisture is absorbed. Therefore, it is necessary to find alternative hole transport materials. In this study, decaphenylcyclopentasilane (DPPS) was selected as a material to modify the perovskite surface, and fabrication of perovskite photovoltaic devices in air and under unsealed conditions was attempted. DPPS is stable in air at temperatures up to 300°C and has the potential to suppress MA desorption; additionally,high-temperature heat treatment can form dense cubic perovskite, which is a stable phase at high temperatures. Polysilane has also been reported to function as a hole transport material, and is also expected to improve photoelectric conversion properties by using the DPPS as a hole transport layer. The fabrication of perovskite photovoltaic devices with DPPS by the air blow method in air could greatly simplify the manufacturing process without using a glove box and stabilize the solar cell characteristics.