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

Abstract

The fabrication of colorless and see-through dye-sensitized solar cells (DSCs) requires the photosensitizers to have little or no absorption in the visible light region of the solar spectrum. However, a trade-off between transparency and power conversion efficiency (PCE) has to be tackled, since most transparent DSCs are showing low PCE when compared to colorful and opaque DSCs. One strategy to increase PCE is applying two cosensitizers with selective conversion of the UV and NIR radiation, therefore, the non-visible part only is absorbed. In this study, we report synthesis of novel five UV-selective absorbers, based on diimide and Schiff bases incorporating carboxyl and pyridyl anchoring groups. A systematic computational investigation using density functional theory (DFT) and time-dependent DFT approaches was employed to evaluate their prospect of application in transparent DSCs. Experimental UV/Vis absorption spectra showed that all dyes exhibit an absorption band covering the mid/near-UV region of solar spectrum, with a bathochromic shift and a hyperchromic shifts for Py-1 dye. Computational results showed that the studied dyes satisfied the basic photophysical and energetics requirements of operating DSC as well as the stability and thermodynamical spontaneity of adsorption onto surface of TiO2. However, results revealed outperformance of the thienothiophene core-containing Py-1 UV-dye, owing to its advantageous structural attributes, improved conjugation, intense emission, large Stokes shift and maximum charge transferred to the anchor. Chemical compatibility of Py-1 dye was then theoretically investigated as a potential cosensitizer of a reference VG20-C2 NIR-dye. By the judicious selection of pyridyl anchor-based UV-absorber (Py-1) and carboxyl anchor-based NIR-absorber (VG20), the advantage of the optical complementarity and selectivity of different TiO2-adsorption-site (Lewis- and Bronsted-acidic) can be achieved. An improved overall PCE is estimated accordingly.

Exploring Different Designs in Thieno[3,4-b]pyrazine-Based Dyes to Enhance Divergent Optical Properties in Dye-Sensitized Solar Cells

“…This strategy was pursued by Han et al [14], who combined the NIR-absorbing squarainebased dye HSQ5 with the UV-absorbing dye Y1, obtaining green-colored DSSC devices with a maximum light transmittance of 60.3% in the 500-600 nm region and a photon-tocurrent efficiency of 3.66%. Hagar et al [15] investigated the theoretical and experimental photo-electrochemical properties of a series of novel diimide and Schiff base UV-absorbers with carboxyl and pyridyl anchoring groups, evaluating their potential co-sensitization with the NIR-absorber VG20 in transparent DSSC. On the other side, Sauvage et al [16] optimized the structure of a polymethine cyanine-based dye (VG20-C 16 ) to absorb only near-infrared light beyond 700 nm: the resulting colorless DSSC devices displayed a 3.1% power conversion efficiency and a remarkable average visible transmittance of up to 76%.…”

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

“…2 Fully transparent and colorless DSCs devices can also be attained with cosensitizers selectively absorbing in the ultraviolet (UV) and NIR regions of the solar spectrum, through which only the nonvisible part of the solar spectrum is converted into electricity. 10,11 Overall, the cosensitization technique is favorable for manipulating solar radiation through the optimum choice of cosensitizers. In the context of greenhouse-integrated DSC agrivoltaics, the manipulation of solar radiation is extremely crucial to maximize the ow of photosynthetically active radiation (PAR) into the interior space of the greenhouse, i.e., blue light (425-475 nm) and red light (625-750 nm), to be captured by chlorophyll a and b pigments, as well as phytochromes in plants, so as to drive photosynthesis.…”