Design and Synthesis of D–A–A-Type Organic Semiconductors for Vacuum-Processable NIR Organic Photodetectors

Although most organic semiconductor materials for organic photodetectors (OPDs) have been developed with a focus on solution processing, vacuum-processable organic semiconductors are highly desirable for practical device manufacturing and integration. Despite these advantages, the development of vacuum-processable organic semiconductors with strong near-infrared (NIR) absorption remains limited. Here, a series of donor–acceptor–acceptor (D-A-A)-type semiconductors are designed by varying fluorine substitution on the terminal acceptor. Fluorination of the terminal acceptor is expected to enhance the electron-withdrawing strength and tune the frontier molecular orbital energies toward long wavelength absorption. Using density functional theory (DFT) calculations, we investigate the effects of fluorination on the optimized molecular structures, frontier molecular orbitals, molecular dipole moment, and bond length alternation (BLA) of the designed molecules.