Optimizing the Cosensitization Effect of SQ02 Dye on BP-2 Dye-Sensitized Solar Cells: A Computational Quantum Chemical Study

Abstract

Cosensitization of the semiconducting electrode in dye-sensitized solar cells (DSCs), with two or more light-harvesting dyes, is a chemical fabrication method that aims to achieve a panchromatic absorption spectrum emulating that of the solar emission spectrum. In this paper, SQ02 and BP-2 cosensitizers have been investigated, as isolated monomers/dimer and adsorbed monomers/dimer on the TiO2 (101) anatase surface, by employing density functional theory (DFT) and time-dependent DFT calculations. Computed results showed that the dominant electron injection pathway is direct injection from each dye into the conduction band of TiO2. The almost complete spectral overlap between the simulated absorption spectrum of BP-2 and fluorescence emissions of SQ02 implies that excitation energy transfer occurs between cosensitizers via the trivial reabsorption mechanism. However, the results showed very limited unidirectional intermolecular charge transfer (CT) from SQ02 dye to BP-2 dye (0.04 |e–|). Therefore, this study also presents a stepwise molecular engineering of BP-2 dye, aiming at optimizing the cosensitization functionality. First, 14 redesigned dye candidates are reported to identify dyes with photophysical properties matching the requirements for efficient DSCs. Second, the four most promising dyes are shortlisted for testing as cosensitizers with the SQ02 dye. The molecular design factors of cosensitization that need validation are chemical compatibility, availability of CT between cosensitizers, and complementarity of the absorption spectra. This screening suggests the judicious choice of the modeled difluorenyl amine donor-based dye (BP-D4) as a very promising cosensitizer. In particular, the SQ02/BP-D4 dimer showed 10 times larger (0.53 |e–|) unidirectional CT than that of SQ02/BP-2 dimer, in addition to the maximum increased electron population of acceptor moieties upon photoexcitation.

UV-selective organic absorbers for the cosensitization of greenhouse-integrated dye-sensitized solar cells: synthesis and computational study

“…Adsorption is usually associated with deteriorating planarity of the adsorbed dyes and increased torsion angles, as a consequence of the steric hindrance induced by the adsorption. 55 Surprisingly, all the simulated optimized geometries of the DI dyes adsorbed on the surface of TiO 2 revealed similar features, i.e. , all torsional angles, excluding angle α , were significantly reduced due to adsorption, when compared to that of isolated dyes ( Table 1 ).…”

“…Moreover, the optimized geometric features reveal that the dyes stay vertically above the TiO 2 cluster surface, with a maximum inclination of ca. 23 detected in the DI-N1 dye.Adsorption is usually associated with deteriorating planarity of the adsorbed dyes and increased torsion angles, as a consequence of the steric hindrance induced by the adsorption 55.…”

On the study of dye sensitized solar cells with high light harvesting efficiency and correlation of its chemical reactivity parameters with overall performance

“…For this test, thiophene has been taken as the common -spacer and 2-Thiohydantoin as the common acceptor motif. Amongst the dyes considered, the dye with donor N1 has shown itself to possess the highest oscillator strength followed by donors diphenyl ethylene benzene [57], 3-oxo-[1, 2, 4]-triazolo[3,4-a]isoquinoline [24] and piperdine-phenyl [57] in the lowest excited state ( rst excited state) which pertains to the maximum probability of light absorption and high light harvesting e ciency. This indicates the much expected higher ability of donor N1 towards absorbing the incoming radiation thereby making it the most suitable donor for further studies.…”

“…al. [24], six different electron rich donor groups have been explored and one such donor (7,7,13,13-tetramethyl-8,9,12,13-…”

Synthesis and Computational Characterization of Organic UV-Dyes for Cosensitization of Transparent Dye-Sensitized Solar Cells

“…Since the emitted photons can be trivially reabsorbed if the absorption and fluorescence spectra of the cosensitizers overlap [ 68 ], the possibility of excitation energy transfer from any of the new synthesized UV-dyes to the proposed VG20 cosensitizer is not expected for the reason that there is no overlapping between absorption spectrum of VG20 (826 nm) and fluorescence spectra of the UV dyes (309–415 nm).…”