Improvement of dye-sensitized solar cells' performance through introducing suitable heterocyclic groups to triarylamine dyes

Dye-sensitized solar cells are currently under intense academic and industrial investigation, owing to their great potential to serve as a low-cost alternative to existing photovoltaic technologies. This paper puts forward a method, which adopts heterocyclic substituted triarylamine units as electronic donor moieties, to design triarylamine dyes for efficient dye-sensitized solar cells. Three novel triarylamine dyes named TTC101, TTC102 and TTC103, were synthesized economically through modification of the structure of a simple triarylamine dye (TC105) using three kinds of heterocyclic groups (4-pyridyl, 2-thienyl and 1-pyrazolyl). The crystal structure of TTC103 indicates that the heterocyclic groups would partly delocalize the positive charge after photooxidation. The overall solar-to-electrical energy conversion efficiencies (η) of TTC102 and TTC103 are 4.92% and 5.21% respectively under AM1.5G irradiation, reaching ～82.3% and ～77.7% of a N719-based reference cell under the same conditions. Besides, the energy conversion efficiencies (η) of TTC102 and TTC103 are 1.29 and 1.37 times the efficiency of TC105 respectively. All of the results above demonstrate that photovoltaic performance can be improved by introducing suitable heterocyclic groups to triarylamine dyes. A series of properties were investigated to explain the results, with a special emphasis on the geometric structures, energetics, and charge transfer processes at the dye/titania/electrolyte interface.