The effect of cyclic thiourea functionalization and β,β′-dialkylbithiophene linker on the performance of triphenylamine dyes

• Four organic dyes containing β,β′-dialkylbithiophene linkers were synthesized.
• The effect of cyclic thiourea functionalization on the performance of dyes.
• The effect of β,β′-dialkylbithiophene linkers on the performance of dyes.
• The effect of geometry configuration of the π-linkers on the performance.

Four new dyes (T-C1, T-C6, S-C1 and S-C6) with β,β′-dialkylbithiophene as π-linkers were synthesized and utilized in dye-sensitized solar cells (DSSCs). Compared with the reference dyes (T-C0 and AZ6) with bithiophene as π-linkers, these dyes show blue-shifted absorption bands, and their DSSCs produce lower short-circuit current and high open-circuit voltage. These may be caused by the increase of dihedral angle between two thiophenes. On the one hand, the molecular conjugations are decreased; on the other hand, steric effect of the whole structures are increased. Compared with the triphenylamine dyes (T-C0, T-C1 and T-C6), the cyclic thiourea functionalized dyes (AZ6, S-C1 and S-C6) exhibit better photophysical and photovoltaic performances. However, the superiority of cyclic thiourea functionalization is gradually disappearing with the increased steric effect of the π-linkers.

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