Tailoring Electronic Properties of SnO₂ Quantum Dots via Aluminum Addition for High-Efficiency Perovskite Solar Cells

Owing to its splendid electrical and optical properties, tin oxide (SnO₂) has been proven to be an effective electron transport layer (ETL) material for high-efficiency perovskite solar cells (PSCs). However, the surface coverage, conductivity, and energy loss at the SnO₂/perovskite interface still have room for improvement. Herein, a facile method by mixing a SnO₂ QD solution with an aluminum (Al) chloride precursor solution at room temperature to achieve the addition of Al into the SnO₂ QD (Al: SnO₂) precursor is proposed. Based on this strategy, conductivity, electron mobility, and band alignment with the perovskite layer have been significantly improved. Besides, the introduction of Al also increases the coverage of the SnO₂ film, consequently contribute to improving the capability to block the charge transfer from FTO to the ETL. Furthermore, fewer defect states are also demonstrated for the perovskite films deposited on Al: SnO₂ films than the control samples. With the optimized addition ratio of 5%, the devices exhibit an average efficiency (PCE) of 17.01%, which is superior to that of the control device of 15.80%. The champion device using Al: SnO₂ ETL delivers an impressive PCE of 18.20%. This research indicates that the low-temperature solution-processed Al: SnO₂ is a promising ETL for high-efficiency PSCs.