Theoretical calculation of photovoltaic properties of novel bis coumarin based Donor-π-Acceptor dyes with different donor and π-bridge moieties for dye-sensitized solar cells

• A novel molecular design strategy to modify both the donor, the π-bridge and its substituted group of bis coumarin derivatives has been theoretically demonstrated. • The photovoltaic performance of the designed twelve dye molecules has been improved in a large degree. • The 3C and 3D dye molecules are suggested to be the most promising organic solar cell materials. Photovoltaic performance is critical for high power conversion efficiencies (PCE) in dye-sensitized solar cells (DSSCs). Here, twelve Donor-π-Acceptor dye molecules were theoretically designed by modifying bis coumarin derivatives by using diethylamine/carbazole/phenoxazine as the donor, bis coumarin as the π -bridge, and cyano substituted acrylic acid (-CH=CCNCOOH) as the acceptor, respectively. Their structures, molecular orbitals, electrostatic potentials, hole and electron distributions, interfragment charge transfer abilities and photovoltaic properties have been calculated and characterized by the DFT and TDDFT methods. The results show that different donor structures have a specific influence on the properties of the designed dye molecules. Based on the calculation equations of power conversion efficiency and filling factor, it can be inferred that the 3C and 3D (see text for definitions) are the most promising organic solar cell materials. From the perspective of theoretical study, this work demonstrates that both the donor, the π -bridge and its substituted group could affect the photovoltaic performance of Donor-π-Acceptor dye molecules in a large degree, providing a new reference for highly efficient research and development of novel DSSC molecules. A schematic novel molecular design strategy to modify both the donor, the π -bridge and its substituted group of bis coumarin derivatives for a promising highly-efficient photoactive layer for the fabrication of dye-sensitized solar cells (DSSCs).