Structural and photophysical investigation of single-source evaporation of CsFAPbI₃ and FAPbI₃ perovskite thin films

Thermal vacuum deposition is a stimulating technique for upscaling perovskite solar cells. However, the operational complexity of multisource vapor deposition (MSVD) and achieving stoichiometric perovskite layers may impede its implementation. The single-source vapor deposition (SSVD) method has recently emerged as an alternative for MSVD due to its inherent functionality and ease of operation. Here, for the first time, we demonstrate a successful SSVD approach for fabricating pure CsFAPbI₃ and FAPbI₃ thin films from pre-synthesized perovskite powders. We carried out structural and photophysical investigations to optimize the phase purity and shelf-life of the deposited thin films. Furthermore, we probed the perovskite layer compatibility with various underlayers; we noted that MeO-2PACz, an organic underlayer, displayed superiority over other organic underlayers such as Spiro-OMeTAD and TaTm, and the SnO₂ metal oxide layer, which might indicate that this method is more suitable for p-i-n solar cell fabrication. Our approach presents a straightforward methodology and avoids the use of multiple thermal sources to deposit CsFAPbI₃ and can further ease the vacuum deposition methodology.