Modeling and Performance Improvement of Organic Tandem Solar Cells Using SCAPS-1D Simulator

This study presents a simulation-based optimization of a two-terminal (2 T) all-polymer tandem solar cell using SCAPS-1D. The structure incorporates PM7:PIDT as the top sub-cell and PM6:PY-IT as the bottom sub-cell. Two key optimization strategies were investigated to enhance device performance. The first involved adjusting the top absorber’s thickness and defect concentration, with optimal values of 200 nm and 10 11 cm −3 , respectively. This configuration yielded a Jsc of 15.1 mA cm −2 , Voc of 2.11 V, FF of 76.7%, and a PCE of 24.5%. The second strategy focused on interfacial engineering by replacing the electron transport layers: TiO 2 was used in the bottom cell and PDINN in the top cell, resulting in Jsc = 11.77 mA cm −2 , Voc = 2.34 V, FF = 83.0%, and PCE = 22.8%. Both approaches outperformed the unoptimized reference device (PCE = 17.2%) and surpassed reported experimental benchmarks (∼17.6%). The thickness-defect optimization alone led to a PCE gain of nearly 9%, underlining the importance of finely tuning material parameters and structure. These findings demonstrate the strong potential of all-polymer tandem solar cells for future flexible and lightweight photovoltaic applications, while offering valuable design guidelines for experimental implementation.