Optimizing g‐C3$_3$N4$_4$‐Based Acceptor Materials Through Density Functional Theory‐Driven Bandgap Engineering for High‐Performance Solar Cells

Graphitic carbon nitride (g‐CN) 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‐CN sheets with various organic moieties. The coupling of g‐CN 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‐CN sheet, along with organic moieties, has reduced from 3.65 eV to 2.26 eV. Among all the composites, g‐CN−4 exhibits the lowest bandgap (2.26 eV), endowing it with excellent optical and electronic properties. Additionally, the angle between the g‐CN 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.