High-efficiency design and optimization of 2 T monolithic polymer/polymer tandem solar cells using SCAPS-1D simulations

Abstract In this study, we present a novel 2 T monolithic polymer/polymer tandem solar cell (TSC) model based on experimentally validated sub-cell designs composed entirely of OSC/OSC polymers. The individual sub-cells have been calibrated against experimental data, resulting in power conversion efficiencies (PCE) of 10.33% for the front cell and 21.72% for the back cell. The lower cell contains a PM6:Y6 active layer in an ITO/Cu2O/PM6:Y6/SnO2/Ag configuration, while the upper polymer cell is designed with a conventional ITO/PEDOT:PSS/PM7:PIDT/PDINN/Ag structure, with PM7:PIDT as the absorber layer. Simulations were performed using the 1D SCAPS tool to individually optimize the performance of each sub-cell. Extensive investigation was carried out on band alignment, defect density, active layer thickness and the selection of electron and hole transport layers (ETLs and HTLs). The effects of temperature, shunt resistance and series resistance on the two sub-cells were also analyzed to improve stability and performance. The resulting tandem structure exhibited a short circuit current density (J SC ) of 11.685 mA cm −2 , an open circuit voltage (V OC ) of 2.0721 V, a fill factor of 82.823% and a PCE of 20.054%, positioning it as a promising candidate for flexible, green and highly efficient tandem solar cells. These results highlight the potential of our design to advance the performance benchmarks of organic tandem solar cells.