Optoelectronic Properties of Mixed Sn/Pb Perovskite Solar Cells: The Study of Compressive Strain by Raman Modes

Mixed Sn/Pb perovskite solar cells offer a suitable alternative pathway to reduce lead toxicity and regulate optical band gap and therefore have significant potential for the development of clean and renewable energy technologies. In this study, the optical and electrical properties of CH3NH3SnxPb1-xI3 [0 <= x <= 1] solar cells under dark conditions were investigated. The compressive strain values of perovskite layers were measured and reported by analyzing the shift of their active Raman modes. Electrical characterizations under dark conditions showed that the values of the threshold voltage (V-th) and inverse saturation current (I-0) of the cells decrease and increase with increasing Sn concentration, respectively. Examination of the behavior of the space charge limited current (SCLC) of cells showed that the presence of Sn atoms increases the ability of the electrical carrier mobility (mu) of cells. Based on the results and calculations, the charge transport mechanism indices including the ideality factor (n), trap-filled limit voltage (V-TFL), trap-state density (n(trap)), and the lifetime of minor carriers (tau(n)) in each of the samples were characterized and reported.