Ga Doping Enables (110) Facet Control and Surface Passivation of SnO2 for Efficient and Stable Inverted Perovskite Solar Cells.

Perovskite solar cells (pero-SCs) with inverted (p-i-n) architecture have advanced rapidly, yet combining high efficiency with long-term operational stability remains challenging, mainly due to commonly used organic cathode buffer layer (CBL) (between C60 electron transporting layer and metal cathode) such as bathocuproine (BCP) with photo-thermal instability. Here, Ga-doped SnO2 (Ga:SnO2) is introduced as an inorganic CBL to replace BCP. Mechanistically, Ga incorporation promotes the preferential growth of the (110) facet of SnO2 nanoparticles, which markedly enhances electrical conductivity and electron mobility of the CBL. It further suppresses non-radiative recombination by passivating surface defects and reducing the interfacial trap density. The improved energy-level alignment at the interface facilitates efficient electron extraction. These synergistic effects-validated by a suite of characterizations-enable inverted pero-SCs with a champion power conversion efficiency of 27.06% (certified 26.77%) and robust stability, retaining 88% of initial efficiency after 1500 h of operation at 85°C. This work demonstrates a viable and scalable pathway to high-performance and long-term stable pero-SCs.