Theoretical studies on the feasibility of the hybrid nanocomposites of graphene quantum dot and phenoxazine-based dyes as an efficient sensitizer for dye-sensitized solar cells.

The feasibility of the hybrid nanocomposites of the graphene quantum dot (GQD) and the phenoxazine-based dyes as the efficient sensitizer of the dye-sensitized solar cell (DSSC) is investigated. Based on the first principles density functional theory (DFT), the geometrical structures of the separate GQDs, the phenoxazine-based dyes, and their hybridized nanocomposites are fully optimized. The energy stabilities of the obtained structures are confirmed by harmonic frequency analysis. The optical absorptions of the optimized structures are calculated with the time-dependent DFT (TDDFT). The feasibility of the nanocomposites as the sensitizer of DSSC is examined by the charge spatial separation, the molecular orbital energy levels of the nanocomposites and the I/I electrolyte, and the conduction band minimum of TiO electrode. The results demonstrate that three of the eight considered nanocomposites satisfy the requirement of DSSC. Among them, GQD4-POXB with large LHE, high V, and enhancement absorption becomes the most promising candidate as a feasible sensitizer. These findings are helpful for the design of the sensitizer of DSSC or the solar energy harvesting materials with the nanocomposites.