Abstract 

Vacuum-compatible fabrication routes for perovskite solar cells (PSCs) are attractive for scalable and reproducible manufacturing, yet their performance remains limited by insufficient control over crystallization and defect formation in vacuum-processed precursors. Here, we demonstrate a PbCl2-mediated chloride-retention strategy by co-evaporating a trace amount of PbCl2 with PbI2 and CsI to form an inorganic precursor, followed by solution infiltration of organic ammonium halides. Precise control of the PbCl2 deposition rate regulates precursor microstructure, facilitates more homogeneous organic-halide infiltration and conversion, and promotes vertically continuous perovskite growth. Cross-sectional scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy analysis shows that chloride-containing species remain detectable after solution conversion and thermal annealing, with the detected Cl content increasing with PbCl2 deposition rate. Structural and photophysical characterizations further reveal that optimized PbCl2 introduction enhances film crystallinity, enlarges grain size, prolongs carrier lifetime, and suppresses defect-assisted nonradiative recombination. Consequently, PSCs fabricated through this hybrid vacuum–solution process exhibit improved charge extraction, partially mitigated hysteresis, and enhanced device-to-device reproducibility. Under 1000 lux TL-84 fluorescent illumination, the optimized devices achieve a power conversion efficiency of 45.71% and retain approximately 90% of their initial efficiency after 1500 h of dark storage in ambient air. These results establish a controllable vacuum-compatible approach for regulating precursor microstructure and preserving chloride-containing species during hybrid perovskite conversion, offering a promising route toward efficient low-light photovoltaics.