Synergic passivation of the interface between TiO2 and perovskite by multifunctional small molecules

Titanium dioxide (TiO2) is widely employed as an electron transport layer in perovskite solar cells due to its low manufacturing cost and favorable energy-level alignment. However, the suboptimal quality of TiO2 films and the presence of multiple defects at the TiO2/perovskite interface, such as uncoordinated Pb2+ and oxygen vacancy defects, significantly compromise both device efficiency and stability. This study proposes a synergistic passivation strategy through the introduction of an acetylamino-functionalized interlayer between the perovskite and TiO2. The acetylamino groups within the passivation layer establish strong interactions with uncoordinated Pb2+ in the perovskite, thereby enhancing interface stability. Acetylamino groups can also interact with the TiO2 layer by bonding with Ti4+ and reducing oxygen vacancy defects, thereby enhancing the electron transport potential of the TiO2 layer. The enhanced hydrophobicity of the TiO2 film, induced by the passivation layer, further promotes perovskite crystallization by minimizing surface tension effects during film growth. Therefore, the device efficiency significantly increased from 16.49% to 19.26%. The lifetime of the unencapsulated device was evaluated under environmental conditions (relative humidity: 30% ± 5%, temperature: 25 ± 5 °C). The efficiency of the unmodified device decreased to 75.3% after 800 h, whereas the modified device maintained 90.1% of its initial efficiency, demonstrating higher stability.