Tuning the Electronic and Optical Properties of Crystalline Anthracene by Doping and Pressure for Photovoltaic Applications

Despite their numerous advantages, organic molecular crystals are often unsuitable for photovoltaic applications due to their poor optoelectronic properties. Here we employ density functional theory to show that the combination of substitutional doping and hydrostatic pressure can effectively tune the structural, electronic, and optical properties of crystalline anthracene. Specifically, we aim to reduce the electronic band gap of crystalline anthracene in order to improve its optical absorption, so that the modified materials become suitable for use in solar cells. Our results reveal that lattice parameters and bond lengths decrease with pressure, hence strengthening interactions between atoms and narrowing the band gap. Doping also reduces the band gap significantly. In the end, three materials studied in the current research display close-to-ideal band gaps: O-doped anthracene under 8.75 GPa of pressure (1.353 eV), P-doped anthracene under 10 GPa (1.073 eV), and S-doped anthracene under 2.5 GPa (1.341 eV). Furthermore, they exhibit high absorption coefficient values on the order of 10⁵ cm^–1 within the visible light range, a noteworthy improvement over pure anthracene. Therefore, we have successfully tuned the optoelectronic properties of crystalline anthracene and identified three ideal candidates for solar cell materials.