Clean and renewable energy development is becoming frontier research for future energy resources, as renewable energy offers sustainable and environmentally friendly alternatives to non-renewable sources such as fossil fuels. Among various renewable energy sources, tremendous progress has been made in converting solar energy to electric energy by developing efficient organic photovoltaics. Organic photovoltaic materials comprising conjugated polymers (CP) with narrow optical energy gaps are promising candidates for developing sustainable sources due to their potentially lower manufacturing costs. Organic semiconductor materials with a high electron affinity are required for many optoelectronic applications. We have designed a series of organic semiconductors comprised of cyclopentadithiophene as a donor and thiadiazoloquinoxaline (TQ) as an acceptor, varying the π-conjugation and TQ-derivatives. We have employed density functional theory (DFT) and time-dependent DFT (TDDFT) to evaluate the designed CP’s optoelectronic properties, such as optical energy gap, dipole moment, and absorption spectra. Our DFT/TDDFT result shows that the energy gap of CPs is lowered and redshifted in the absorption spectra if there is no insertion of conjugation units such as thiophene and selenophene between donor and acceptor. In addition, selenophene shows relatively better redshift behavior compared to thiophene. Our work also provides rational insight into designing donor/acceptor-based CPs for organic solar cells.

π-conjugated organic material, specifically, the modification of donor acceptor-based dyes, has gained significant attention over the years for its outstanding performance in efficient dye-sensitized solar cells (DSSCs) as well as contributing to overall economically sustainable solar cell technology. In the present study, density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches were executed to investigate the impact of benzobisselenadiazole (BBSD) based organic dyes with interchangeable donor and acceptor units on their optical properties. Two spacers were selected from 27 π-linker models due to their better performance on the absorption spectra. A total of 200 BSSD dyes were designed based upon the above two selected spacers linking with various donors and acceptors. The corresponding structures and properties were theoretically analyzed by DFT/TDDFT methods. D10A8-16 and D10A6-17 show the best performance and may become the best candidates to be developed as efficient dye sensitizers for DSSCs. Our results showed that structural changes can effectively improve the optoelectronic properties of the designed BSSD dyes. This provides us with an economic and fast screening way for artificial design of new dyes.