Interfacial chemical bridge constructed by l-cysteine for highly efficient perovskite solar cells

The layered structure of perovskite solar cells determines the importance of interfaces. However, the differences in compositions and energy level always cause the undesired interface contact and defects fatally, especially for the SnO2/perovskite interface. These poor contacts and defects can influence the interface electron transfer and recombination dynamics. Therefore, modifying the SnO2/perovskite interface is necessary. Herein, we incorporate the L-cysteine as the interfacial chemical bridge between SnO2 and perovskite. The higher electron concentration at -COOH of L-cysteine depends it can link to -OH on SnO2 preferentially, and then the outward facing -NH2 and -SH can coordinate with Pb, realizing the tight connection between SnO2 and perovskite and accelerating the interface charge extraction. Besides, the coordination between L-cysteine and Pb depends that L-cysteine modification can regulate the crystallization and growth dynamics of perovskite and reduce the interface Pb defects. The performance parameters suggest that L-cysteine modification can promote the device performances.