Two-Dimensional BAs/InTe: A Promising Tandem Solar Cell with High Power Conversion Efficiency.

Tandem solar cells (SCs) connecting two sub-cells with different absorption bands have the potential to reach the commercialized photovoltaic standard. However, the performance improvement of tandem architectures is still a challenge primarily owing to the mismatch of bandgaps in two sub-cells. Here, we demonstrate a two-dimensional (2D) BAs/InTe-based tandem SC, which could reach solar-to-electric efficiency higher than 30%. Firstly, the narrow bandgap of hexagonal single-layer BX (X = P and As) and wide bandgap of single-layer YZ (Y = Ga and In, Z = S, Se, and Te) are found to have high thermodynamic stability based on density functional theory calculations. Next, considering narrow and wide bandgaps at the HSE06 functional, single-layer BX/YZ-based tandem SCs are built to effectively capture broadband solar spectrum by combining such two sub-cells. Since the bandgap of single-layer BAs matches well with InTe monolayer, the power conversion efficiency of BAs/InTe-based tandem SC can reach as high as 30.2%. Moreover, it is important to note that the used materials, including few-layer GaZ and InSe, have been experimentally prepared, which strongly supports the high feasibility of the designed 2D tandem SCs in this work. Our constructed 2D-materials-based devices can be competitive in realizing commercialized high-performance tandem SCs.