g-ZnO/HfGe2N4 heterojunction: A novel semiconductor for efficient photocatalysis and optoelectronic detector applications

The g-ZnO/HfGe₂N₄ heterojunction, based on g-ZnO and HfGe₂N₄, has been successfully constructed, aiming to achieve efficient applications in photocatalysis and optoelectronic detection. The stability of this heterojunction has been verified through first-principles calculations, and its electronic and optical properties have been explored. Subsequently, its application in catalysis is investigated, calculating the band edge positions for photocatalysis, the Gibbs free energy for Hydrogen Evolution Reaction and Oxygen Evolution Reaction, and the Solar-to-Hydrogen (STH) efficiency. A significant modulation of STH efficiency under conditions of biaxial strain is achieved. Ultimately, optoelectronic device models are constructed along both the armchair and zigzag orientations. Quantum transport simulation calculations are then employed to investigate the characteristics pertinent to photodetector functionality. It is found that the g-ZnO/HfGe₂N₄ heterojunction is Type II semiconductor with a direct bandgap of 0.72 eV. It exhibits high absorption in the visible light region, significantly enhancing the performance in the field of photocatalysis compared to the intrinsic material. The STH efficiency is as high as 50.84 %, which can be modulated by applying biaxial strain. The photocurrent response of this heterojunction is significant, with a photocurrent response as high as 2.02 a₀²/photon in the armchair direction. The extinction ratio in the zigzag direction is 163.7. These findings provide an important theoretical basis and experimental guidance for the design and development of new high-efficiency optoelectronic materials and photocatalysts.