All‐Vacuum‐Processing for Fabrication of Efficient, Large‐Scale, and Flexible Inverted Perovskite Solar Cells

Vacuum deposition of transporting layers, especially the hole‐transporting layer (HTL), is still a big challenge for the fabrication of large‐area perovskite solar cells (PSCs). In this work, efficient and large‐area PSCs are fabricated by thermal evaporation of all the layers. Poly(bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine) (PTAA) is used as the HTL, and a compact layer of PTAA with low thickness (2–10 nm) is successfully deposited using thermal evaporation. The optical and ultraviolet photoelectron spectroscopy (UPS) measurements prove that the evaporated PTAA has a great match with the single A‐cation methylammonium triiodide perovskite film in terms of quenching effect and band alignment. After fabrication of the inverted architecture using all‐vacuum‐processing, PSCs with power conversion of efficiencies (PCEs) of 19.4% for small area (0.054 cm²) and 18.1% for large area (1 cm²) are achieved, which are higher than those of solution‐based devices. A flexible PSC with PCE of 17.27% is also fabricated using this approach. Moreover, the fabricated PSCs, using the vacuum technique, show negligible hysteresis and good stability, better than the devices fabricated on spin‐coated PTAA. This work highlights the potential of vacuum deposition for scale‐up and commercialization of PSCs.