Acid molecule-assisted high-quality SnO2 transport layer for perovskite solar cells

The SnO2 electron transport layer (ETL) serves a critical role in perovskite solar cells. However, the oxygen vacancy defects and excess hydroxyl (–OH) groups in SnO2 always lead to degradation of device performance. Herein, we introduce iminodiacetic acid (IDA) to modify the SnO2 ETL, yielding three key advantages: (1) IDA can neutralize excess –OH groups and passivate the defects in SnO2, diminishing the decomposition of perovskite layer; (2) the IDA-modified SnO2 exhibits superior electron conductivity and film quality, while providing improved energy level alignment with the perovskite layer; and (3) the IDA-modified SnO2 owns superior surface wetting properties that facilitates a more effective perovskite crystallization. Ultimately, the devices based on IDA-modified SnO2 obtain a champion efficiency of 24.02% and enhanced stability.