Electronic and Optical Properties of Functionalized Dihydroxyanthraquinone as Potential Organic Semiconductor Materials for Solar Cells Applications

The electronic and optical properties of three dihydroxyanthraquinone organic molecules─anthrarufin, chrysazin, and quinizarin─were theoretically investigated as potential candidates for organic solar cells. Using density functional theory (DFT), key electronic properties such as reorganization energy (λ), adiabatic ionization potential (IA), adiabatic electron affinity (EA), HOMO, LUMO, and energy gap (E_gap) were calculated. Time-dependent DFT (TD-DFT) was employed to determine optical properties, including maximum absorption (λ_max) and oscillator strengths (f) at excited states in both a vacuum and solvent. Additionally, nonlinear optical properties, such as polarizability and first hyperpolarizability, were evaluated. Global reactivity descriptors, including dipole moment (μ), electronegativity (χ), hardness (η), softness (S), and electrophilicity index (ω), were also calculated. The impact of functionalization on these molecules’ properties was examined to understand its effects and provide guidelines for designing and synthesizing new derivatives with enhanced properties for use as semiconductors in organic electronics. The results indicate a correlation between the type and position of functional groups, reorganization energies, and predicted charge transport properties. Functional groups such as CN lower both λ_h and λ_e, making them promising candidates for n-type materials. The position and type of functional groups significantly affect global properties like dipole moment and energy gap (E_gap), with quinizarin exhibiting the lowest dipole moment (0.97 D) and variations reaching up to 10.76 D. To further understand the intermolecular interactions of the examined molecules, Hirshfeld surface analysis and energy framework studies were conducted.