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.
Highlights
Introduction of of the the BDTABDTA spacer spacer and and acceptor acceptor externally externallyin in(a) (a)RB RB55and and(b) (b)RB 10dye. dye.The reactive dye−based sensitizers were obtained by the functional modification of dyes (RB 5−Et, reactive blue 5 (RB 5)−NO2, reactive brown 10 (RB 10)−Et, and RB 10−NO2) and by the introduction of BDTA π−spacer to form a donor−π−acceptor type system (RB 5−BDTA, RB 5−BDTA−A, RB10−BDTA, and RB 10−BDTA−A)
The reactive dye−based sensitizers were obtained by the functional modification of dyes (RB 5−Et, RB 5−NO2, RB 10−Et, and RB 10−NO2) and by the introduction of BDTA
All the RB 5 Dye-based sensitizers showed the presence of a hydrogen bond between the H atom of the –NH group and the electronegative O atom of the –SO3 H group that resided in its close vicinity
Summary
Over the years, unprecedented human population growth, technological advances, and industrial sectors have necessitated an increased energy supply. One of the most efficient and widely used strategies employed in designing the dye sensitizers is to have a donor-π bridge-acceptor (D-π-A) bipolar configuration. This dye sensitizer structure can induce the intramolecular charge transfer from the donor part to the acceptor part during photo-excitation. It is favored for effective charge separation and the injection of photoexcited electrons into the conduction band of photoanode material. The enhancement in the electronic properties of the organic counterpart was monitored with the introduction of a π-spacer between the intramolecular donor-acceptor regions Another strategy of attaching the π-spacer to the dye molecule by an acceptor unit was tried. The electrostatic potential maps, electron localization function, the density of states (DOS) plot, and the HOMO-LUMO were obtained to understand the effect of functional groups and π-spacer on the electronic properties of the modified reactive dyes
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