Blue phosphorene/MoSi ₂N ₄ van der Waals type-II heterostructure: Highly efficient bifunctional materials for photocatalytics and photovoltaics

Converting solar energy into electric power or hydrogen fuel is a promising means to obtain renewable green energy. Here, we design a two-dimensional blue phosphorene (BlueP)/MoSi ₂N ₄ van der Waals heterostructure (vdWH) and investigate its potential application in photocatalysis and photovoltaics using first-principles calculations. We find that the BlueP/MoSi ₂N ₄ vdWH possesses type-II band structure with a large build-in electric field, thus endowing it with a potential ability to separate photogenerated electron–hole pairs. The calculated band-edge positions show that the heterostructure is a very promising water-splitting photocatalyst. Its solar-to-hydrogen efficiency ( η _STH) can reach up to 15.8%, which is quite promising for commercial applications. Furthermore, the BlueP/MoSi ₂N ₄ vdWH shows remarkably light absorption capacity and distinguished maximum power conversion efficiency ( η _PCE) up to 10.61%. Remarkably, its η _PCE can be further enhanced by the external strain: the η _PCE of 21.20% can be obtained under a 4% tensile strain. Finally, we determine that adjusting the number of the BlueP sublayer is another effective method to modulate the band gaps and band alignments of the heterostructures. These theoretical findings indicate that BlueP/MoSi ₂N ₄ vdWH is a promising candidate for photocatalyst and photovoltaic device.