Facilitating the formation of SnO2 film via HfO2-modified FTO electrode for efficient perovskite solar cells

Fabricating a dense and crystalline SnO2 film has been an important step for efficient SnO2-based perovskite solar cells (PSCs). Herein, a wide bandgap material, HfO2, was deposited on the surface of FTO to facilitate the formation of an SnO2 film. It was found that the HfO2 modification on FTO could significantly improve the crystallization of the upper SnO2 film and passivate the trap states within the SnO2 layer. Moreover, the high conduction band level of HfO2 can block the backflow of electrons and suppress the nonradiative recombination of carriers. Eventually, the best PSC with HfO2 interlayer presented a power conversion efficiency (PCE) of 21.13% with a VOC of 1.13 V, which are higher than those of the reference device. This study provides a meaningful strategy for ETL optimization to further increase the efficiency of the SnO2-based PSCs.