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Based on the first-principles calculations of density functional theory, the stability, electronic structure, and optical properties of single layer GeC, N-doped, As doped, and N-As doped GeC systems were systematically studied. The results show that the single layer GeC is a direct bandgap semiconductor with the bandgap of 2. 10 eV. Compared with the single layer GeC, the bandgap and work function of the doped system decrease, indicating that the required energy for electronic transition is relatively small in our doped system. Moreover, the light absorption coefficient of the doped system improves, and the absorption band edge has also undergone a red shift, effectively expanding the response range of the system to light and improving the absorption ability of the system to photons. In addition, the As doped GeC system not only exhibits impurity levels near the Fermi level, but also shows the optimal optical properties such as absorption coefficient, static dielectric function, and extinction coefficient in the low energy region. The above research can provide a theoretical basis for the preparation of relevant GeC photoelectric experiments. [ABSTRACT FROM AUTHOR]

The stability, electronic structures, work function, and optical properties of single-layer g-C3N4 and X/ g-C3N4 (X = g-C3 N4 , AlN and GaN) heterostructures were investigated using plane-wave density functional theory with ultra-soft pseudopotentials. The results show that the lattice mismatch ratio and lattice mismatch energy of X/ g-C3N4 heterojunction are very low, indicating that X/ g-C3N4 heterojunction has excellent stability. Compared with the single-layer g-C3N4, the bandgap of the X/ g-C3N4 all reduces, and the peaks and troughs of the density of states greatly improves. At the same time, X/ g-C3N4 has a redshift, which leds to an increase in the number of electrons in the excited state, making electronic transitions easier. It shows that the heterojunction is beneficial to improves the response-ability of the system to visible light, and effectively improves the photocatalytic activity of the system. Further calculations show that the work function of X/ g-C3N4 reduces and a built-in electric field is formed at the interface, which inhibits the recombination of photo-generated electron-hole pairs. This is of great benefit to the migration of carriers and the improvement of photocatalytic ability. Among them, the GaN/ g-C3 N4 heterojunction has the smallest work function, the potential difference at the interface formed a built-in electric field and the redshift is the most obvious. It can be inferred that the GaN/ g-C3 N4 heterojunction has the best photocatalytic activity. Therefore, the heterojunction proposed in this paper is an effective means to improve the photocatalytic activity of the system. [ABSTRACT FROM AUTHOR]