Interface engineering with single-walled carbon nanotubes for high-efficiency (> 29%) lead-free BaSnS₃ perovskite solar cells: insights from numerical simulation

Abstract The search for efficient, lead-free perovskite solar cells motivates the exploration of stable chalcogenide absorbers like BaSnS₃. To address the need for systematic interface engineering in these devices, this SCAPS-1D simulation study investigates the integration of a single-walled carbon nanotube (SWCNT) interlayer. We first optimize an FTO/TiO₂/BaSnS₃/P3HT/Ag baseline cell, achieving a power conversion efficiency (PCE) of 26.05%. By introducing and optimizing a SWCNT layer, the PCE is boosted to 29.15%—an absolute gain of 3.10% points. Our analysis deconvolutes this enhancement, attributing it to improved charge extraction (increased fill factor to 86.19%), a higher built-in potential, and extended near-infrared absorption. A sensitivity analysis confirms the robustness of this gain even with more realistic SWCNT parameters. The study provides clear design rules and quantifies the theoretical performance ceiling for SWCNT-engineered interfaces, offering a valuable guide for experimental development of high-efficiency, lead-free chalcogenide perovskite photovoltaics.