Interfacial defect passivation by chenodeoxycholic acid for efficient and stable perovskite solar cells

Passivating the surface defects of perovskite has become one of the important strategies to suppress non-radiative recombination and improve the photovoltaic performance and stability of perovskite solar cells (PVSCs). Herein, we introduce chenodeoxycholic acid (CDCA) on the surface of perovskite layer. The infrared spectra and nuclear magnetic resonance (1H NMR) spectra prove the carboxyl (–COOH) group on CDCA combination with the formamidinium (FA+) ions on perovskite. The water-contact angle measurement indicates that the long alkyl chain of CDCA covers the surface of perovskite film. The photoelectrical characterization demonstrates that the surface defects of the perovskite layer are passivated and carrier non-radiative combinations are suppressed. Under an optimized CDCA concentration of 0.2 mg⋅ml−1, the CDCA passivated PVSC achieves an average power conversion efficiency (PCE) of 20.41%, as compared with the pristine PVSC with an average PCE of 18.18%.