Monolithic all-perovskite tandem solar cells: advancing sustainable energy options

Abstract

This paper discusses the results of a simulation-based study on lead-free perovskite tandem devices. Wide bandgap (1.8 eV) perovskite materials Cs2AgBi0.75Sb0.25Br6 as the top cell and narrow bandgap (1.3 eV) perovskite materials CsSnI3 as the bottom cell make up the simulated tandem cell device, respectively. The optimisation process involves individually fine-tuning both cells under standard solar radiation conditions of 100 W/m2. The tandem cells necessitate precise current matching between the two sub-cells. The current matching condition manifests at Jsc of 16 mA cm−2 when the top and bottom cells reach an optimised thickness of 700 nm and 65 nm, respectively. The optimised tandem cell achieves a 24.47% power conversion efficiency (PCE), a high Voc of 1.7278 V, and a high fill factor of 83.72%. Furthermore, tandem solar cells’ temperature dependence is examined in the 300 K to 400 K range, revealing that efficiency decreases with temperature due to a reduction in Jsc (short-circuit current). Notably, the current matching condition is primarily influenced by the top cell, which exhibits less variation than the bottom cell. This study paves the way for developing tandem solar cells made entirely of lead-free perovskites and presents a new approach for the experimental realisation of high-power conversion efficiency.