Optimizing g-C 3 $_3$ N 4 $_4$ -Based Acceptor Materials Through Density Functional Theory-Driven Bandgap...

Graphitic carbon nitride (g-C ${}_3$ N ${}_4$ ) is a nonmetallic semiconductor that has garnered significant attention in the field of energy conversion and storage. This interest is due to its exceptional properties, including a moderate bandgap, high thermal and chemical stability, cost-effectiveness, and optimal conduction and valence band positions. In this study, we have designed and investigated a series of composite materials integrating g-C ${}_3$ N ${}_4$ sheets with various organic moieties. The coupling of g-C ${}_3$ N ${}_4$ sheets with wide-gap organic molecules (we have termed them "composite materials") results in a reduction of the bandgap in the composite materials. Interestingly, the bandgap of the g-C ${}_3$ N ${}_4$ sheet, along with organic moieties, has reduced from 3.65 eV to 2.26 eV. Among all the composites, g-C ${}_3$ N ${}_4$ -4 exhibits the lowest bandgap (2.26 eV), endowing it with excellent optical and electronic properties. Additionally, the angle between the g-C ${}_3$ N ${}_4$ sheet and the organic molecular plane became ≈ 90°, which minimizes the recombination rate of electron-hole pairs. By emphasizing the bandgap engineering of these composites, this work offers a strategy to enhance optoelectronic activity through the introduction of foreign organic moieties into the matrix.