Theoretical investigation of charge transport properties of X-type carbon-based organic semiconductor molecules

In this study, quantum chemical calculations were performed using the 6–31 + G(d,p) basis set and long-range-corrected functionals (CAM-B3LYP and WB97XD) to optimise the structures and evaluate the charge transfer rates of five X-type carbon-based molecules. These molecules are hexa-peri-hexabenzo[a, d, g, j, m, p]coronene-based systems with azulene rings at the four end corners, with the edge carbon atoms replaced by B–N, B–O, B–S, or C = O groups. The results indicate that all five X-type molecules are quasi-planar, conjugated large π-systems, classifying them as organic semiconductors. The carrier mobility (μ) values calculated using WB97XD are relatively higher, although the trends remain consistent across methods. The B–N hybridised molecule (e) exhibits the highest hole mobility (μ₊), 1.8 times its electron mobility (μ_-), thus making it a strong candidate for hole transport and suitable for p-type semiconductor applications. Conversely, the B–O hybridised (c) and B–S hybridised (d) molecules demonstrate electron mobility (μ_-) 2.8 and 4.5 times higher than their hole mobility (μ₊), indicating their suitability as high-performance n-type organic semiconductor materials.