Simulation of a High‐Efficiency MASnI 3 /SWCNT Tandem Solar Cell Using SCAPS‐1D

The performance of perovskite solar cells (PSCs) is strongly related to their ability to absorb and utilize incident sunlight. In this work, we design and simulate a MASnI 3 /single‐walled carbon nanotube (SWCNT) tandem solar cell. Unlike conventional configurations using Si‐based bottom cells, the proposed lead‐free MASnI 3 /SWCNT architecture employs SWCNT as a carbon‐based bottom absorber to enhance utilization of long‐wavelength photons transmitted through the MASnI 3 top sub‐cell. The simulations were performed using the Solar Cell Capacitance Simulator in one dimension (SCAPS‐1D), where the top and bottom sub‐cells were modeled separately and treated as two series‐connected diodes under current‐matching conditions. The top sub‐cell adopts an FTO/TiO 2 /MASnI 3 /Au structure without a hole transport layer, while the bottom sub‐cell uses an ITO/ZrS 2 /SWCNT/Au structure. Key parameters, including electron transport layer properties, absorber thickness, defect density, and doping concentration, were optimized. Under the optimized configuration, with a 400 nm MASnI 3 layer and a 2 µm SWCNT layer with a 1.0 eV bandgap, the tandem cell achieves a of 1.69 V, a of 22.13 mA cm − 2 , an FF of 84.68%, and a PCE of 31.67%. These results suggest that the MASnI 3 /SWCNT architecture provides a promising numerical design strategy for high‐efficiency lead‐free tandem photovoltaic devices.