Single-Source Vapor-Deposition of MA_1–xFA_xPbI₃ Perovskite Absorbers for Solar Cells

Vapor deposition of halide perovskites presents high potential for scalability and industrial processing of perovskite solar cells. It prevents the use of toxic solvents, allows thickness control, and yields conformal and uniform coating over large areas. However, the distinct volatility of the perovskite organic and inorganic components currently requires the use of multiple thermal sources or two-step deposition to achieve the perovskite phase. In this work, single-source, single-step MA_1–xFA_xPbI₃ thin film deposition with tunable stoichiometry by pulsed laser deposition is demostrated. By controlling the laser ablation of a solid target containing adjustable MAI:FAI:PbI₂ ratios, the room temperature formation of cubic α-phase MA_1–xFA_xPbI₃ thin films is demonstrated. The target-to-film transfer of the ablated species, including the integrity of the organic molecules and the desired MA⁺:FA⁺ ratio, is confirmed by x-ray photoelectron spectroscopy and solid-state NMR. Photoluminescence analysis further confirms the shift of the bandgap with varying the MA⁺:FA⁺ ratio. Finally, proof-of-concept n-i-p solar cells with 14% efficiency are demonstrated with as-deposited non-passivated pulsed laser deposition (PLD)-MA_1–xFA_xPbI₃. This study opens the path for future developments in industry-compatible vapor-deposition methods for perovskite solar cells.