Stable and Efficient Graded MA_0.83Cs_0.17Pb(I_0.83Br_0.17)₃ Alloy Thin Film-Based Inverted-Type Perovskite Solar Cells

The surface morphologies, crystallinities, and excitonic characteristics of MA_xCs_1−xPb(I_xBr_1−x)₃ thin films deposited on top of the P3CT-Na/ITO/glass substrates are investigated by using the atomic-force microscopic images, absorbance spectra, grazing incidence X-ray diffraction patterns, photoluminescence (PL) spectra, and Raman scattering spectra. The P3CT-Na-based perovskite solar cell shows a stable and efficient maximum power density curve due to the formation of a graded MA_0.83Cs_0.17Pb(I_0.83Br_0.17)₃ alloy thin film which is confirmed by using the surface-sensitive PL and Raman scattering spectra. The highest power conversion efficiency (PCE) of the P3CT-Na-based MA_0.83Cs_0.17Pb(I_0.83Br_0.17)₃ solar cells is 15.93% mainly due to the high fill factor of 79.4%. Besides, the PCE of the nonencapsulated solar cell slowly decreases to a moderate value (10.48%) within 157 days under an uncontrolled environment (55–60 relative humidity%) at room temperatures (22–25 °C).