Insights from Density Functional Theory on the Feasibility of Modified Reactive Dyes as Dye Sensitizers in Dye-Sensitized Solar Cell Applications

Abstract

Recently, reactive dyes have attracted a lot of attention for dye-sensitized solar cell applications. This study endeavors to design dye sensitizers with enhanced efficiency for photovoltaic cells by modifying the reactive blue 5 (RB 5) and reactive brown 10 (RB 10) dyes. Three different strategies were used to design the sensitizers, and their efficiency was compared using the density functional theory (DFT). The optimized geometry, bang gap values, the density of states, electrostatic potential surface analysis, and theoretical FT-IR absorption spectra of the sensitizers were obtained. In the first strategy, functional groups (electron-donating (C2H5), electron-withdrawing (–NO2) groups) were anchored onto dye molecules, and their effect on the charge transport properties was evaluated using the DFT analysis. The latter two designs were based on a donor-π-acceptor strategy. The second design consisted of intramolecular donor-acceptor regions separated by a benzodithiophene-based π-spacer. In the third strategy, an external acceptor unit was attached to the dye molecules through the benzodithiophene-based π-spacer. The electron-donating strengths of donor moieties in the donor-π-acceptor systems were studied using B3LYP/6-31G level DFT calculations. The quantum chemical analysis of the three designs revealed that the anchoring of functional groups (–NO2 and C2H5) on the dye molecules showed no impact on the charge transport properties. The introduction of a benzodithiophene-based π-spacer improved the conjugation of the dye sensitizers, which enhanced the electron transport properties. The electron transport properties further improved when an external acceptor unit was attached to the dye molecule containing a π-spacer. It was thus concluded that attaching an external acceptor unit to the donor dye molecule containing a π-spacer produced desired results for both of the dyes.