Minimizing open-circuit voltage loss in perovskite solar cells through synergistic energy-level grading and lattice matching
MAPbI3 perovskite solar cells (PSCs) exhibit a theoretical open-circuit voltage (VOC) of approximately 1.3 V, yet practical devices suffer from substantial VOC loss due to interfacial charge recombination and energy-level misalignment. This study introduces SrTiO3 nanocubes as an interfacial layer between the TiO2 electron transport layer (ETL) and MAPbI3 absorber to synergistically address these losses. The SrTiO3 interlayer facilitates optimal energy-level alignment with the MAPbI3 conduction band, reducing charge carrier energy loss and enhancing electron extraction. Additionally, the minimal lattice mismatch between SrTiO3 and MAPbI3 promotes the growth of high-quality perovskite films with reduced defect density. Time-resolved photoluminescence (TRPL) measurements reveal that the SrTiO3-modified sample exhibits a prolonged slow decay lifetime of 54 ns and an average carrier lifetime of 60.72 ns, compared to 45.20 ns for the control. Consequently, the VOC of MAPbI3 PSCs increases to 1.17 V, and the power conversion efficiency (PCE) reaches 22.19%, up from 19.95% for the control. Stability tests under 25% relative humidity and 25 °C show that unencapsulated SrTiO3-based PSCs retain approximately 92% of their initial PCE after 500 h, whereas control devices degrade to 74%. This work demonstrates that synergistic energy-level grading and lattice matching via SrTiO3 interface engineering effectively minimizes VOC loss and enhances both efficiency and stability of MAPbI3 PSCs.