Multifunctional buried interface modification for efficient and stable SnO2-based perovskite solar cells

Multifunctional buried interface modification is key to boost the performance of perovskite solar cells (PSCs). Herein, a multifunctional passivator, N-(2-hydroxyethyl) ethylene diamine triacetic acid trisodium salt (HEDTA-3Na), is employed to modify an SnO2 electron transport layer (ETL) for fabricating efficient and stable PSCs. It is found that the addition of HEDTA-3Na not only reduces defect state density by passivating uncoordinated Sn4+ and Pb2+ defects in an ETL/perovskite interface, but also forms appropriate energy band alignment, facilitating electron extraction, and improves the quality of the perovskite film with enlarged grain sizes. In addition, the Na+ ions can diffuse into the perovskite layer to passivate iodine vacancy defects and inhibit ion migration. As a result, the PSC with HEDTA-3Na modification achieves a champion PCE of 23.11% with enhanced VOC and FF compared to the control device (20.82%). Moreover, the unencapsulated HEDTA-3Na-modified PSC retains 90% of its initial efficiency after 1600 hours at 25 degrees C and 20-25% relative humidity under ambient conditions. This work offers a simple and effective approach to synergistically improve the performance of PSCs with a single multifunctional molecule.