Novel Ru(II) Complex with 1H-Benzo[d]lmidazole Derivative for Dye-Sensitized Solar Cell

It was reported that ruthenium(II) complex CBTR with 1H-benzo[d]imidazole derivative for heteroleptic donor system exhibited an enhancement of the solar cell performance, compared to N3. We took a theoretical approach about the CBTR dye. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations were used to gain insight into the factors responsible for the photovoltaic properties of the dye sensitizer. The values of the absorption spectrum of the CBTR dye with the 1 H-benzo[d]imidazole derivative were not improved compared to those of the N3 dye. The lack of improvement was attributed to the destabilization of the lowest unoccupied molecular orbital (LUMO) energy level of the CTBR dye. According to the molecular orbital analysis, the LUMO of the CBTR dye mainly localized on the dcbpy (dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) moiety. The highest occupied molecular orbitals (HOMOs) of N3 were localized on the Ru-NCS moiety, and the HOMOs of CBTR were also localized on Ru-NCS. The introduction of the 1H-benzo[d]imidazole derivative to the heteroleptic donor system did not change the location of the HOMOs. The addition on of the NHC ligand to the CBTR dye seems to be an essential structural modification to enhance the efficiency of solar cells.