Amidine thiourea as a multifunctional modifier of buried interface for effective perovskite solar cells with reduced lead leakage

Abstract

The defects at buried SnO 2 /perovskite interface can influence the performances of perovskite solar cells by causing the poor perovskite crystallinity, bad interface connection, undesired interfacial recombination and electron transfer efficiency. Now, multifunctional amidine thiourea is used to modify the buried SnO 2 /perovskite interface. The amidine thiourea can passivate the interface defects by the electron donation roles of N and S atoms, improve the electron transfer efficiency by enhancing the interface connection and regulating the interface energy level matching, reduce lead leakage and reinforce the structural stability of device by the coordination and hydrogen bond interaction. The perovskite solar cells with the amidine thiourea modification exhibit an enhanced power conversion efficiency (20.48%) and stability, outperforming than that of control device (18.65%). Modifying the buried interface with small organic molecule is a feasible and efficient method to improve the performances of PSCs. The amidine thiourea interface chemical bridge can accelerate the interface charge extraction by realizing the tight connection and regulating the energy level matching of SnO 2 /perovskite interface. Besides, amidine thiourea can passivate the oxygen vacancy defects on SnO 2 and the uncoordinated Pb defects on perovskite. In addition, the strong chemical interaction between ADT and Pb can reduce the lead leakage in device. After modifying the SnO 2 /perovskite interface with amidine thiourea, the power conversion efficiency and stability of device are all improved. • Amidine thiourea (ADT) is used to modify the buried SnO 2 /perovskite interface. • ADT can passivate the buried oxygen vacancy defects and uncoordinated Pb 2+ defect. • ADT can enhance connection and regulate energy level matching at buried interface. • ADT can reduce lead leakage through strong chemical interactions. • ADT-modified devices exhibit enhanced power conversion efficiency and stability.