Predominant Stable MAPbI₃ Films Deposited via Chemical Vapor Deposition: Stability Studies in Illuminated and Darkened States Coupled with Temperature under an Open-Air Atmosphere

Although the use of perovskite materials in solar cells has drawn a tremendous amount of attention because of rewarding power-conversion efficiency of 22.1%, concerns persist that poor stability will hinder the commercial viability of perovskite-based photovoltaic devices. Chemical vapor deposition (CVD) is the most suitable technology for commercialization and could potentially provide a future perspective for stable and efficient perovskite-based electronic devices. Until now, systematic investigation has addressed neither the preparation nor the intrinsic stability of these materials under both dark and illuminated conditions given the high humidity of perovskite films deposited by CVD. In the present study, we investigated the stability of perovskite films under dark and illuminated conditions coupled with temperature under an open-air atmosphere via the tuning of various deposition parameters. CVD-deposited MAPbI3 films with no additives showed structural and optical properties at a predominant level of stability for ∼2000 h in dark and ∼1000 h under ambient room lighting, which achieved a significantly higher level of stability than that of either solution-processed perovskite films with or without additives, or for composites with polymers. The outstanding stability of CVD-deposited MAPbI3 films is attributed to their large grain sizes with high levels of crystalline quality and chemical purity.