Excellent Intrinsic Thermally Stable Coevaporated LiF:C ₆₀ Layers Mitigate Interface Defects and Charge Losses in Fully Vacuum‐Processed Perovskite Solar Cells

Despite being one of the most promising candidates for emerging market opportunities, all‐vacuum‐deposited perovskite solar cells (PSCs) still suffer from significant efficiency limitations, primarily due to open‐circuit voltage ( V _OC ) losses caused by interfacial defects at the top surface of the perovskite layer. In this work, we demonstrate PSCs fabricated via a simple, sandwich‐type all‐vacuum thermal evaporation process, incorporating an ultrathin (6 nm) MS‐OC (spiro[fluorene‐9,9′‐phenanthrene‐10′‐one] incorporated with o ‐phenylcarbazole) hole transport layer (HTL) as a growth template for hybrid metal–halide perovskites. To mitigate V _OC losses and better understand the interfacial charge dynamics, we systematically investigate various electron transport materials (ETMs), with a particular focus on C ₆₀ , LiF, and coevaporated C ₆₀ :LiF (1:1). Our results reveal that the C ₆₀ :LiF (1:1) coevaporation strategy not only suppresses fullerene aggregation but also effectively passivates the perovskite surface, thereby reducing nonradiative recombination and enhancing V _OC by 23.37%. As a result, the power conversion efficiency (PCE) of the PSCs improved by 29.34%, reaching a PCE of 13.4% with low nonradiative loss (~135 mV). More importantly, this composite passivation approach significantly enhanced the device's environmental stability, maintaining 90% of its initial efficiency after 600 h of operation.