Simulation and optimization of perovskite solar cells with multifunctional polymer interlayers at the perovskite/HTM interface

Abstract Perovskite solar cells (PSCs) are currently of great interest due to their high efficiencies and low costs. Despite the progress made, there remain opportunities for further improvement. The use of semiconducting polymer intermediate layers (IL) is a valuable strategy to enhance both the efficiency and stability of these cells. Aiming to optimize the devices for maximum efficiency, this work presents numerical simulations using SCAPS of solar cells with the structure: FTO / c-TiO2 / m-TiO2 / CH3NH3PbI3 / IL / Spiro-OMeTAD / Au. In these cells, the ILs are P3HT and PTB7-Th polymer monolayers, as well as a PTB7-Th/P3HT bilayer, placed between the perovskite absorber (CH3NH3PbI3) and the hole transport layer (Spiro-OMeTAD). The theoretical models were calibrated against experimental results. The effects of various parameters (absorber thickness, interlayer thickness, hole transport layer thickness, absorber defect density, and anode work function) on the output characteristics (Jsc, Voc, FF, and efficiency) of the cells were examined. In the optimized devices, the polymer type used in the interlayer had little effect on Jsc and Voc but significantly influenced the FF (79.45%, 81.58%, and 84.52% for cells with PTB7-Th/P3HT, PTB7-Th, and P3HT interlayers, respectively). The highest efficiency obtained in this study (25.31%) was achieved with the P3HT interlayer solar cell, using thicknesses of 1400 nm, 100 nm, and 15 nm of CH3NH3PbI3, Spiro-OMeTAD and P3HT layers, respectively, with a low defect density in the absorber (1010 cm-3) and an anode work function of 5.1 eV. This work provides valuable insights into the role of polymer interlayers in optimized devices, identifies the most efficient structure, and offers a way to develop high-efficiency solar cells while keeping costs low.