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

Tandem solar cells (SCs) connecting two subcells 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 band gaps in two subcells. Here, we demonstrate a two-dimensional (2D) BAs/InTe-based tandem SC, which could achieve solar-to-electric conversion efficiency higher than 30%. First, the narrow band gap of hexagonal single-layer BX (X = P and As) and wide band gap 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 band gaps at the HSE06 functional, single-layer BX/YZ-based tandem SCs are built to effectively capture a broad-band solar spectrum by combining such two subcells. Since the band gap of single-layer BAs matches well with that of the 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-material-based devices can be competitive in realizing commercialized high-performance tandem SCs.