Efficient, ambient-air-processed perovskite solar cells achieved through synergistic defect passivation at the SnO2/Perovskite interface with guanidinium sulfamate

The buried interface in perovskite solar cells (PSCs) plays a pivotal role in charge transfer and device stability, simultaneously influencing perovskite film growth. Here, we employ guanidine sulfamate (GAS) as a multifunctional passivator to simultaneously modify the SnO 2 electron transport layer (ETL) and perovskite bottom surface, significantly enhancing the performance of n-i-p structured PSCs. Computational results indicate that GAS molecules effectively bind to defect sites and significantly increase the energy barriers for defect formation, thereby suppressing the generation of V I , Pb I , and Pb i defects. Experimentally, we demonstrate that this binding mechanism involves the sulfonate groups (-SO 3 H) of GAS forming stable coordination bonds with undercoordinated Sn 4+ sites and oxygen vacancies in the SnO 2 ETL. This effectively passivates these defects and reduces their concentration within the SnO 2 lattice. Concurrently, the guanidinium cations (-NH 2 ) establish strong coordination bonds with uncoordinated Pb 2+ or I − ions in the perovskite layer, decreasing defect states at grain boundaries and interfaces, thereby suppressing non-radiative recombination. As a result, GAS-modified perovskite devices from ambient-air-process achieve a high open-circuit voltage ( V OC ) of 1.157 V and a power conversion efficiency (PCE) of nearly 24.00 %. Furthermore, compared to control devices, GAS-based PSCs exhibit superior ambient stability.