A dye molecule based on the bacteriochlorin (Bacteriochlorins are planar, highly conjugated macrocyclic molecules [1]), LS-01, as a sensitizer in the dye-sensitized solar cells (DSSCs) has been investigated. This molecule has a D-π-A architecture (bacteriochlorin as donor, ethynyl-phenyl as π spacer and carboxylic acid as anchoring/acceptor group) that via an anchoring group is connected to the TiO2 surface. In this work, a possible relationship between the dye structure and the performance of the DSSC has been investigated. The dye was optimized at the DFT/M06-2X/6-31G(d,p) level of theory [2]. Excited state calculations were done by using the TD-DFT/M06-2X/6-311++G (d,p) level of theory. The dihedral angle of dye between anchored group and π spacer, π spacer and donor moiety are ~ 0.13° and ~ 0.7° respectively. Therefore, this good planarity can increase the π-conjugation and facilitates the injection of photoexcited electrons into the TiO2 semiconductor. The results of the DFT and TD-DFT calculations show the negative values for ΔGing. (-1.690 eV), which means that the electron injection process from the excited dye to the TiO2 is spontaneous. This result is accordance with the structural planarity mentioned above.

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