Iminodiacetic Acid-Modified TiO2 Electron Transport Layers for Efficient and Stable All-Inorganic CsPbIxBr3-x Perovskite Solar Cells

The electron transport layer (ETL) plays a decisive role in governing the photovoltaic performance of perovskite solar cells (PSCs). This study demonstrates a facile yet effective strategy of incorporating iminodiacetic acid (IDA) as a low-cost, multifunctional dopant into hydrothermally synthesized titanium dioxide (TiO2) ETLs. This modification enables multidimensional defect passivation at the TiO2 bulk, the surface, and the TiO2/perovskite interface, significantly boosting device performance. Specifically, the dicarboxyl groups in the IDA molecule coordinate with Ti ions and oxygen vacancies on the TiO2 surface, effectively passivating deep-level traps and enhancing electron mobility. Simultaneously, the imino groups facilitate the formation of a dense, high-crystallinity CsPbIxBr3-x perovskite layer through coordination with uncoordinated Pb 2+ ions. Consequently, the optimized device (5 mg/mL IDA) delivers a champion power conversion efficiency (PCE) of 12.16%, representing a significant absolute enhancement of 3.38% over the unmodified control (8.78%). Furthermore, the modified devices exhibit markedly reduced hysteresis (from 0.024 to 0.011) and superior stability, retaining over 82% of their initial efficiency after 1000 h of continuous simulated sunlight irradiation. This work provides a cost-effective and industrialization-compatible technical avenue for fabricating high-performance all-inorganic PSCs via molecular interface engineering.