Thiazolo[5,4-d]thiazole-based organic sensitizers with strong visible light absorption for transparent, efficient and stable dye-sensitized solar cells

Abstract

A small set of thiazolo[5,4-d]thiazole-based D-π-A organic dyes, endowed with bis-pentylpropylenedioxythiophene (ProDOT) moieties in the π-spacer, was designed with the aid of computational analysis, synthesized and characterized. The presence of bulky and electronrich ProDOT groups beside the electronpoor thiazolothiazole unit induced optimal physico-chemical properties, including broad and intense visible light absorption. As a consequence, the dyes resulted particularly suitable for application in thin layer dye-sensitized solar cells (TiO2 thickness: 3.0-6.5 µm). Small-scale (0.25 cm2) devices prepared using standard materials and fabrication techniques gave power conversion efficiencies up to 7.71%, surpassing those obtained with two different reference dyes. Transparent larger area cells (3.6 cm2) also showed good η values up to 6.35%, not requiring the use of a co-adsorbent, and retained their initial efficiency over a period of 1000 h storage at 85°C. These results make this new family of organic sensitizers promising candidates for successful application in the production of efficient and stable transparent DSSCs for building-integrated photovoltaics

Towards Sustainable H2 Production: Rational Design of Hydrophobic Triphenylamine‐based Dyes for Sensitized Ethanol Photoreforming

“…Finally, to study the effect of the spacer moiety, dye AD418, in which the double bond was replaced by a thiophene ring, was also prepared and tested together with the known, more elaborated dyes TTZ3–TTZ5. TTZ dyes have an electron‐withdrawing thiazolo[5,4‐ d ]thiazole moiety in the π‐scaffold and are characterized by long‐term stability and by very high molar extinction coefficients, which has made them especially suitable for the fabrication of thin‐layer DSSCs (Figure ) . TTZ4 and TTZ5 carry hydrophobic chains both on the central scaffold and on the donor moiety, whereas TTZ3 only has chains on its central scaffold.…”

“…TTZ4 displayed only slightly higher TON values than TTZ3, whereas TTZ5 showed a much higher H 2 production activity (slightly higher than 3400 μmol g −1 , Table ), relatively close to AD418, suggesting that alkyl sulfide substituents on the donor have a beneficial effect in the photocatalytic process. Notably, TTZ5 was also the best‐performing sensitizer among TTZ dyes in recent DSSC studies …”

Photoactive Compounds Based on the Thiazolo[5,4‐d]thiazole Core and Their Application in Organic and Hybrid Photovoltaics

“…[92] In the same period, several unsymmetrical D-π-A compounds, each featuring a thiazolothiazole moiety in the conjugated bridge, were reported to act as photosenzitizers in dye-sensitized solar cells, and a maximum efficiency of 7.71 %, [121] coupled with satisfactory stability of over 1000 h, [122] was observed in the presence of electron-rich propylenedioxythiophene (ProDOT) substituents.…”

“…The stability of such strip cells, constructed with dyes TTZ3-5, was also tested through monitoring of their photovoltaic parameters over a period of 1000 h, during which they were stored at 85°C in the dark: all devices showed excellent stability, and their power conversion efficiencies stayed basically constant during the entire period of time. [122] Finally, the different TzTz-containing dye 41 (Figure 8), based on a rather unconventional π-D-A architecture, was also reported. [123] The synthesis of compound 41 was very similar to that of FNE71-74, but with inversion of the Vilsmeier-Haack formylation and bromination/Suzuki-Miyaura coupling steps: in the resulting structure the TzTz-thiophene unit is located in a terminal position rather than between the donor and the acceptor moieties.…”

“…The dyes' photoand electrochemical properties were modulated by introducing structural modifications both on the donor group (TTZ3-5 and 7) and on the π scaffold (TTZ6). [121,122] The absorption maxima of TTZ3-7 are shifted to longer wavelengths relative to TTZ1-2 (510-521 vs. 472-476 nm), with particularly high molar extinction coefficients between 8.14 and 9.67 × 10 . Such bathochromic shift could be explained by the presence of the ProDOT groups, which are more electron-rich and less aromatic than simple thiophenes thanks to electron donation from their additional oxygen atoms.…”