UV-Assisted Interfacial Oxygen Desorption for High-Performance Hole-Conductor-Free, Printable Mesoscopic Sn-Pb...

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 TiO₂ (m-TiO₂) electron transport layer within this architecture readily chemisorbs oxygen molecules, generating reactive species that aggressively oxidize Sn²⁺ to Sn⁴⁺ and degrade device performance. Herein, we propose a UV-assisted O₂ desorption strategy to deactivate the m-TiO₂ 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 Sn²⁺ oxidation by surface-adsorbed oxygen, preserves the Sn-Pb lattice integrity, suppresses non-radiative recombination, and optimizes carrier dynamics at the modulated TiO₂/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 N₂ atmosphere.