High-Efficiency Novel Cu ₃ InSnS ₅ Quantum Dot Photovoltaics: From Quantum Confinement Modeling to Tandem Cell Optimization for Dual Indoor/Outdoor Energy Harvesting

This study presents a comprehensive numerical optimization of single and tandem photovoltaic cells utilizing novel Cu 3 InSnS 5 colloidal quantum dots (CQDs) as absorbers. These quaternary CQDs have emerged as a compelling class of low-dimensional materials due to their tunable optoelectronic properties and compliance with the Restriction of Hazardous Substances (RoHS) directive. A multi-scale simulation framework is employed, combining the envelope function approximation to predict size-dependent quantum confinement effects, Rigorous Coupled-Wave Analysis (RCWA) for optical modeling, and the Solar Cell Capacitance Simulator (SCAPS-1D) for device-level electrical optimization. By systematically tuning the CQD radius, buffer layer, and absorber thickness, the optimized single-junction cell achieves a power conversion efficiency of 11.53% under standard AM1.5G illumination, significantly surpassing the current experimental benchmark of <0.1%. Furthermore, a tandem architecture is designed to minimize thermalization losses, yielding an impressive efficiency of 31.97% under AM1.5G. Under indoor LED illumination (1250 lx), the single and tandem cells attain efficiencies of 12.13% and 22.21%, respectively. These findings underscore the immense potential of Cu 3 InSnS 5 CQDs for dual indoor/outdoor energy harvesting, particularly for powering low-light Internet of Things (IoT) devices.