Lead and Iodide Fixation by Thiol Copper(II) Porphyrin for Stable and Environmental-Friendly Perovskite Solar Cells

Abstract

The formation of undersaturated lead or iodide ions and I2 on the perovskite surface can decrease the performance and stability of perovskite solar cells (PSCs). Additionally, the leakage of noxious lead limits the application of PSCs. Here, we develop a strategy for molecular modulation of a perovskite surface using thiol copper(II) porphyrin (CuP) to post-treat the perovskite film. The Raman spectra reveal that the CuP molecules anchor on the perovskite surface by a coordination interaction between the thiol-terminal of CuP and Pb ion in perovskite. DFT calculations demonstrate that the porphyrin core in CuP has a strong fixing effect on I− and I2 by the induction force and electrostatic attraction. Such a fixation was demonstrated by the shift of the UV absorption peak of I2 in solution with the addition of CuP and the decreased defects density in the CuP-treated perovskite film. Finally, the modified PSCs exhibit an improved cell performance with the best efficiency up to 21.76% (certified 20.97%). The modified PSCs acquired significantly improved stability. In addition, there is almost no lead leakage from the treated film immersed in water. This work provides a surface modulation strategy by thiol CuP treatment to fabricate efficient, stable, and environmental-friendly PSCs.