Design and Computer-Aided Chemical Calculations of Hetero ring Containing Acceptor-Typed Compounds

Fullerene-free acceptors containing heterocycles are promising organic layers for photovoltaic devices, because the power conversion efficiency (PCE) of fullerene-free organic solar cells is higher than that of fullerene-based cells. In this study, banana-shaped, fullerene-free acceptor molecules (M1–M5) with a donor–acceptor–donor structure were designed by attaching conjugated triphenylamine groups to a 1,2,4-triazole core, building on furan-substituted triazole compounds previously synthesized and studied computationally by our group. Computer-aided chemical calculations used density functional theory (DFT) at the B3LYP/6-31G(d,p) level, and excited-state energies were obtained by time-dependent DFT within the Tamm–Dancoff approximation in the gas phase, chloroform, and dimethyl sulfoxide. The most stable conformers of all molecules adopted a banana-shaped geometry. Triphenylamine doping reduced the calculated HOMO–LUMO band gap relative to the parent compounds (for example, from about 3.9 eV for compound 1 to 2.62 eV for M1), while solvent polarity had little effect on the band gaps or frontier-orbital distributions. These results provide a theoretical basis for synthesizing the designed molecules and testing them in organic solar cells.