Theoretical insight on hybrid nanocomposites of graphene quantum dot and carbazole-carbazole dyes as an efficient sensitizer of DSSC.

Abstract

The feasibility of the hybrid nanocomposites of the graphene quantum dot (GQD) and carbazole-carbazole dyes as the efficient sensitizer of dye-sensitized solar cells (DSSC) is investigated. By using the first principles density functional theory (DFT), we fully optimize the geometrical structures of GQD, the carbazole-carbazole dyes, and their hybrid nanocomposites. The harmonic frequency analysis is used to confirm the energy stability of the optimized structures. The optical absorptions of the structures are calculated with the time-dependent DFT (TDDFT). Using the I-/I3- electrolyte and the conduction band minimum of TiO2 electrode as a sample, we examine the feasibility of the nanocomposites as the sensitizer of DSSC with the charge spatial separation and the molecular orbital energy levels of the nanocomposites. The results demonstrate all the considered nanocomposites have suitable energy levels of the frontier orbitals and significantly charge spatial separation. TDDFT results show the oscillator strengths of all nanocomposites demonstrate the obvious enhancement in the visible light region. Moreover, the appropriate open-circuit voltage value, the larger light-harvesting efficiency, and larger driving force are also identified for these nanocomposites. Therefore, the nanocomposites could be the more promising candidates of sensitizer for DSSC in comparison with the separate carbazole-carbazole dyes.