Optical properties of CsFAMA-based perovskite film and its application in the inverted solar cells with poly(methyl methacrylate) passivation layer

We reported the basic optical properties of a triple cation CsFAMA perovskite film and its application in the inverted p-i-n solar cells. The exciton binding energy of 42 meV and the refractive index of 2.4 is obtained from the temperature-dependent photoluminescence spectra and spectroscopic ellipsometry measurement, respectively. The results indicate that CsFAMA lead halide perovskite is an excellent light-absorbing material. The inverted p-i-n CsFAMA perovskite solar cells with PMMA passivation layer are studied, and the optimized PCE can be increased to 16.90% with a negligible hysteresis effect. The long-term and thermal stabilities of CsFAMA perovskite solar cells can be improved after PMMA passivation, which maintains 81% (40% relative humidity, 25 °C, 720 h) and 91% (50% relative humidity, 100 °C, 6 h) of initial efficiencies, respectively. This work provides a promising method for stable and low-cost inverted perovskite solar cells.