UV‐Assisted Interfacial Oxygen Desorption for High‐Performance Hole‐Conductor‐Free, Printable Mesoscopic Sn‐Pb Perovskite Solar Cells

Integrating tin‐lead (Sn‐Pb) perovskites, with their high hole conductivity and ideal bandgap, into fully printable, hole‐conductor‐free mesoscopic perovskite solar cells (p‐MPSCs) using carbon electrodes offers a promising potential toward high‐efficiency, low‐cost photovoltaics. However, the mesoporous TiO 2 (m‐TiO 2 ) electron transport layer within this architecture readily chemisorbs oxygen molecules, generating reactive species that aggressively oxidize Sn 2+ to Sn 4+ and degrade device performance. Herein, we propose a UV‐assisted O 2 desorption strategy to deactivate the m‐TiO 2 surface. Under a nitrogen atmosphere, UV irradiation effectively triggers the desorption of adsorbed oxygen species, resetting the interface to a chemically inert state. Comprehensive electron paramagnetic resonance and X‐ray photoelectron spectroscopy analyses systematically validate this “surface cleansing” effect. The treatment suppresses Sn 2+ oxidation by surface‐adsorbed oxygen, preserves the Sn‐Pb lattice integrity, suppresses non‐radiative recombination, and optimizes carrier dynamics at the modulated TiO 2 /perovskite interface. Consequently, the devices achieve a champion power conversion efficiency of 10.55%, the first demonstration of Sn‐Pb p‐MPSCs, obviously outperforming control devices (9.38%). Moreover, inhibiting interfacial oxidation yields prolonged storage longevity, with unencapsulated cells retaining 93% of their initial efficiency after 1250 h in the N 2 atmosphere.