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.

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It is well known that electron transport layer (ETL) plays an indispensable role in the planar heterojunction perovskite solar cells (PSCs). TiO2 is widely used as an ETL material due to its excellent transport properties, however, the presence of defects in the TiO2 layer diminishes the power conversion efficiency (PCE) of the devices. Herein, we introduce a method of low-temperature TiCl4 treatment to deposit a TiOx layer on the surface of TiO2 film, which can effectively passivate trap states at the TiO2 surface. Moreover, the treating process is optimized to be 30[Formula: see text]min using a 40[Formula: see text]mM TiCl4 aqueous solution. Benefiting from this, we obtain the champion device with the highest PCE of 18.47%, which is mainly due to the reduction of surface defects and the deposition of the well-crystallized perovskite films. Besides, the modified PSCs exhibit an average PCE of 17.59%, which is much better than the control devices.