Sensitizers designed toward efficient intramolecular charge separation for p-type dye-sensitized solar cells

Effective charge separation is demonstrated as one of the rational design strategies for organic sensitizers of both n-type and p-type dye-sensitized solar cells. Herein, we report the design and synthesis of novel D-A dye cTPAPh-NO2 and D-A(1)-A(2) dye cTPABT-PyCN2 using triphenylamine as the donor, di-carboxylic acid group as anchoring group. Photophysical and electrochemical properties of both dyes were investigated to discuss the effect of anchoring group and molecular structure on the photophysical processes and charge separation feature of the sensitizers. For D-A dyes, the attachment of carboxyl groups reduces both the light harvesting and intramolecular charge separation ability of cTPAPh-NO2. In comparison, cTPABT-PyCN2 exhibits weak fluorescence and efficient intramolecular charge separation characteristics. Exceeding 80% of cTPABT-PyCN2 singlets decays via intramolecular electron transfer from the first acceptor to the dicyanovinyl pyrimidine. Finally, these synthesis dyes were used as sensitizers in p-type DSSCs and cTPABT-PyCN2 showed the overall power conversion efficiency of 0.103%, which is comparable to that of reported dyes. The results demonstrate that D-A(1)-A2 structure can be a promising strategy to design p-type sensitizers with effective charge separation characteristics.

Automated summary

The design and synthesis of two novel D-A dyes cTPAPh-NO2 and cTPABT-PyCN2 were reported, and their photophysical and electrochemical properties were investigated. The attachment of carboxyl groups reduced the light harvesting and intramolecular charge separation ability of cTPAPh-NO2. In contrast, cTPABT-PyCN2 exhibited weak fluorescence and efficient intramolecular charge separation characteristics. These dyes showed promising potential as p-type sensitizers with effective charge separation characteristics in dye-sensitized solar cells.