Multifunctional interface engineering enables high efficiency of semi-transparent CsPbBr3 solar cells

All-inorganic semi-transparent perovskite solar cells fabricated via vapor deposition techniques exhibit enormous commercial potential. However, high-temperature solid-state reactions induce abundant defects on CsPbBr 3 surfaces, and electron-beam-deposited NiO X further impairs perovskite surface integrity, rendering the perovskite/NiO X interface highly susceptible to redox reactions and severely limiting photovoltaic performance. Herein, we propose a multifunctional interfacial engineering strategy: spray-coating a potassium bromodifluoroacetate (KBDFA) layer on the perovskite surface to form an interfacial network. This isolates the perovskite/NiO X interface and mitigates perovskite damage during electron beam evaporation. Furthermore, KBDFA's acetate groups coordinate with coordinatively unsaturated Pb 2+ ions, while K + stabilizes Br − ; halogen species also fill Br − vacancies, achieving synergistic defect passivation. Meanwhile, the high electronegativity of fluorine increases the Ni ≥3+ content in NiO X , thereby enhancing the conductivity of the hole transport layer. KBDFA modification also optimizes interfacial energy level alignment, enabling efficient hole extraction. The optimized device achieved a 7.78% power conversion efficiency (PCE) and maintained an average transmittance (AVT)of 52.63%—a state-of-the-art benchmark for vapor-deposited semi-transparent CsPbBr 3 solar cells—with excellent humidity and light stability. The corresponding 10 cm × 10 cm module (with an active area of 64 cm 2 ) delivers a respectable PCE of 3.92%.