A two-dimensional α-As/α-AsP van der Waals heterostructure for photovoltaic applications

On the basis of first-principles calculations, we constructed a two-dimensional (2D) α-As/α-AsP van der Waals heterostructure (vdWH) to study the structural stability, and electronic and optical properties. Our results show that the 2D α-As/α-AsP vdWH displays indirect semiconductor characteristics with a band gap of 0.86 eV. Furthermore, it exhibits anisotropic properties and a high light absorption coefficient of up to 10⁶ cm^-1 in the ultraviolet region. Our predicted photoelectric conversion efficiency (PCE) of the 2D α-As/α-AsP vdWH reaches 21.30%, which is higher than those of blue-AsP/CdSe (13%), GeSe/AsP (16%), and As/tetracyanonaphtho-quinodimethane (TCNNQ) (20%). By applying an in-plane strain in the range from -6% to 6%, the band structure of the 2D α-As/α-AsP vdWH can be effectively tuned. In particular, under a uniaxial strain of -2% along the x-axis (2% along the y-axis), a transition from indirect to direct in the band structure occurs, while when applying a biaxial strain of -4% a transition from a semiconductor to a metal can be realized. These results indicate that the 2D α-As/α-AsP vdWH has potential applications in optoelectronic devices and solar cells.