The influence of the position and quantity of thiophene or acetylene groups on the photoelectric properties of dye-sensitized solar cells.

To investigate the influence of the position and quantity of thiophene or acetylene groups on the photoelectric properties of dye-sensitized solar cells (DSSCs), density functional theory (DFT) were employed to simulate five zinc porphyrin dye molecules (T-3, T-3-D, T-3-A, T-3-AD, and T-3-ace). The optimized geometry indicated that T-3-ace possessed superior planar properties, attributed to incorporating the acetylene groups, facilitating the charge transfer process. The lower lowest unoccupied molecular orbital (LUMO) energy levels of T-3-ace and T-3-D suggested that introducing thiophene or acetylene groups on the donor side enhanced the electron absorption capability of the dyes. The analysis of optical properties revealed that the incorporation of thiophene or acetylene groups on the donor side (T-3-D or T-3-ace) exhibited a more prominent red shift and a broader absorption range, which was beneficial for promoting electron excitation and optical properties. The low reorganization energy suggested these two molecules have better structural stability during photoexcitation. The prediction of photoelectric conversion efficiency (PCE) showed that introducing thiophene was beneficial for improving the PCE, with the most significant effect observed when introducing thiophene groups on the donor side (T-3-D). The T-3-ace demonstrated the highest maximum short circuit current density J; however, the lower electron injection efficiency (φ) led to a lower short circuit current density J and consequently a lower PCE. This work is conducive to providing valuable insights into the molecular structure of zinc porphyrin dyes and their photoelectric properties.