Numerical simulation of all-inorganic two-terminal AlSb/Al0.15Ga0.85Sb tandem solar cell with high-open circuit voltage (>1.90 V) and >40% conversion efficiency

Tandem solar cells, with monolithically integrated wide bandgap top cell and narrow bandgap bottom cell, have the potential to surpass the Shockley-Queisser limit in single junction solar cells. Antimony (Sb) based compound semiconductors are promising candidates for tandem photovoltaics due to their wide range of tunable bandgaps, non-toxicity, low-cost and natural abundance. In this study, we use numerical simulations to evaluate the performance of a novel two-terminal (2T) all-inorganic tandem solar cell. The top cell consists of AlSb as the main absorber layer, which has a bandgap of 1.60 eV. The bottom cell has Al0.15Ga0.85Sb absorber having a bandgap of 0.852 eV. The short-circuit current density of the top cell matches that of the bottom cell when the Al0.15Ga0.85Sb thickness is 370 nm. The defect densities of the top and the bottom cell absorber layers are optimized to maximize the performance of the tandem cell. Under current matching conditions, the optimized 2T tandem cell yields a high-open circuit voltage (Voc) of 1.91 V leading to a power conversion efficiency of 40.95%. The results presented here can aid in the development of the next generation of highly efficient all-inorganic tandem solar cells.