Two Novel Carbazole Dyes for Dye-Sensitized Solar Cells with Open-Circuit Voltages up to 1 V Based on Br−/Br3− Electrolytes

Dye-sensitized solar cells (DSCs) based on two novel carbazole dyes (TC301 and TC306) and a Br−/Br3− redox mediator in dried CH3CN solutions as electrolytes yielded a Voc of 1.156 V and a η value of 3.68% and a Voc of 0.939 V and a η value of 5.22% under simulated AM 1.5, respectively. The dyes TC301 and TC306 have more positive HOMO levels (1.59 and 1.38 V vs NHE) than the redox potential of Br−/Br3−-based electrolytes, which have sufficient driving force to regenerate dyes. Under similar conditions with an I−/I3− instead of a Br−/Br3− redox mediator, DSCs sensitized by the dyes TC301 and TC306 produced a Voc of 0.696 V and a η value of 2.36% and a Voc of 0.621 V and a η value of 4.10%, respectively.