Cyclic thiourea functionalized dyes with binary π-linkers: Influence of different π-conjugation segments on the performance of dye-sensitized solar cells

• A series of cyclic thiourea functionalized dyes containing binary π-linkers were synthesized for DSSCs.
• Increase of short-circuit current by introducing electron-rich segments and broadening absorption band.
• Increase of open-circuit voltage by increasing steric hindrance.
• Binary π-linker bearing 3,4-ethylenedioxythiophene-thiophene shows both large steric hindrance and good conjugated coplanarity.

A series of cyclic thiourea functionalized dyes containing binary π-linkers were synthesized and applied in the dye-sensitized solar cells. The only difference of these dyes is that one segment of the binary π-linkers is thiophene, n-hexylthiophene, thienothiophene, 3,4-ethylenedioxythiophene, and benzene, respectively. Among them, the dyes incorporating electron-rich thienothiophene or 3,4-ethylenedioxythiophene exhibit the broader absorption bands and higher molar extinction coefficients in the visible region, which can not only enhance the light-harvesting ability but also improve the short-circuit current density; on the other hand, the dyes bearing bulky n-hexylthiophene or 3,4-ethylenedioxythiophene can effectively suppress the intermolecular π–π aggregation and electron recombination owing to larger steric hindrance, which is beneficial to increase the open-circuit voltage.

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