A novel graded approach for improving the efficiency of Lead-Free perovskite solar cells

Abstract

Methylammonium tin iodide (MASnI3) is the most commonly used lead-free perovskite absorber material to resolve the issues related to toxic lead (Pb)-based MAPbI3 perovskite. However, conversion efficiency for MASnI3-based perovskite solar cells (PSCs) are still struggling to compete with lead-based PSCs. Therefore, this study provides a roadmap to achieving 22.3 % conversion efficiency for MASnI3-based PSCs through extensive device modeling. The work utilizes the graded active layer approach to attain higher excitons inside the active layer. The opto-electrical model's combined effort is considered an excellent light trapping mechanism by matching precise bandgaps 1.3 eV/1.3 eV for a higher generation of excitons. Detailed investigation and optimization of single, double, and triple graded perovskite absorber layer (PAL) have been done in terms of absorber layer thickness, temperature, back contact materials, and bulk defect density to achieve a conversion efficiency of 22.3 %. Results revealed that double-graded perovskite outperforms compared to single and triple-graded material and delivered excellent photovoltaic (PV) parameters such as short circuit current density (JSC) of 33.51 mAcm−2, open-circuit voltage (VOC) of 875 mV and fill factor (FF) of 75.93 %. This paper provides a smooth pathway for futuristic development and further optimization of the device lead-free MASnI3-based PSCs.