Boosting the efficiency of lead-free MASnI3 perovskite solar cells through a bilayer CIGS structure approximating a gradient bandgap distribution

Abstract

This study develops a novel dual-absorber solar cell structure to enhance the efficiency of lead-free perovskite solar cells. Using SCAPS-1D simulations, the performance of single-layer lead-free perovskite solar cells and double-absorber layer (perovskite/CIGS) solar cells was evaluated, with independent optimization of parameters for each configuration. The results show a significant 20% increase in efficiency for the double-absorber structure compared to traditional single-layer designs. By introducing a bilayer CIGS structure approximating a gradient bandgap distribution, this study leverages the tunable bandgap properties of CIGS to improve device performance, achieving a short-circuit current density of 38.80 mA cm⁻² and a power conversion efficiency of 33.08%-values that have not been achieved in previous dual-absorber structures. The gradient bandgap CIGS layer significantly enhances light absorption and carrier collection while minimizing performance losses due to recombination. Additionally, the study explores the energy band structure, electric field distribution, and rates of carrier generation and recombination within the device, providing insights into the carrier generation mechanisms in the absorber layer and their recombination at interfaces. These findings demonstrate the potential of gradient bandgap CIGS layers to advance lead-free perovskite solar cell technology.