Single‐source evaporation of CH ₃ NH ₃ SnI ₃ for Pb‐free perovskite solar cells

Abstract

Summary Sn‐based perovskite is the most promising candidate as environmentally benign and Pb‐free perovskite; however, the nonuniform morphology of Sn‐based perovskite thin films caused by rapid crystallization is a major issue. We demonstrate how pure CH3NH3SnI3 (CH3NH3 = methylammonium, MA) thin films can be uniformly deposited by the single‐source evaporation of presynthesized MASnI3 crystals. The perovskite crystals are synthesized by cooling crystallization under an ambient atmosphere and sublimed without decomposition by controlling the heating rate. The evaporated thin films were postannealed at various temperatures and times, which resulted in a pinhole‐free microstructure with an average grain size of 423 nm. The average power conversion efficiency (PCE) of planar‐type solar cells based on the optimized perovskite thin films was 1.7% ± 0.1%.

Origins and Suppression of Sn(II)/Sn(IV) Oxidation in Tin Halide Perovskite Solar Cells

“…Ultimately, the TPSCs obtained a certified PCE of 14%. [118] In summary, optimization of the deposition process of tin perovskite films can effectively avoid Sn(II)/Sn(IV) oxidation by: i) avoiding the Sn(II) transfer process; [109] ii) prioritizing the preparation of single crystals to avoid the adverse effects of direct formation of perovskite films from halides; [112,119] iii) avoiding the participation of intermediates (solvents, additives, etc.) during the tin perovskite formation process; [110,113,114] iv) regulating the crystallization of tin perovskite films to achieve dense films to prevent water and oxygen intrusion.…”

“…However, some processes and devices' structure applicable to LPSCs are not suitable for TPSCs, such as the preparation of tin perovskite by evaporation and solution post-treatment with IPA as solvent. [119,123] Because of the chemical differences between Sn and Pb, these preparation methods could destroy tin perovskite and induce oxidation. At present, reports on the unique preparation technology and device structure of TPSCs are very limited.…”

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

“…27 In recent work single-source evaporation of CH 3 NH 3 SnI 3 for Pb-free PSCs reached a PCE of 1.7%. 28…”