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 I-2 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 I-2 by the induction force and electrostatic attraction. Such a fixation was demonstrated by the shift of the UV absorption peak of I-2 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.