We report the preparation of MASnxPb1−xI3 (0 ≤ x ≤ 1) thin films by three-source vapor deposition and provide the first systematic investigation of the full compositional range fabricated under identical processing conditions, enabling direct comparison across the series. Mixed perovskite formation is confirmed across all compositions, with the absorption edge red-shifting as Sn content increases. In contrast to solution-processed systems, the bandgap shows no pronounced bowing, reaching ∼1.38 eV at low Sn compositions. Solar cells fabricated for each composition exhibit a nearly linear decrease in performance with increasing Sn fraction. Radiative-limit analysis reveals open-circuit voltage losses exceeding those expected from bandgap narrowing alone, indicating strong non-radiative recombination. Photoelectron spectroscopy reveals that Sn incorporation induces progressive p-type doping, therefore suggesting Sn oxidation in the tin-containing films. Targeted defect-control strategies and refined growth optimization during vapor deposition are therefore needed to unlock the potential of evaporated, narrow-bandgap Sn-based perovskites.
Martínez‐Goyeneche et al. (Mon,) studied this question.