Performance enhancement of dye-sensitized solar cells with organic dyes

Dye in the dye-sensitized solar cells (DSSCs) is firstly electron launching part by visible light absorption and is located at interface between TiO₂ and electrolyte. We have studied organic dye with an interaction control effect between TiO₂ and electrolyte for the recombination inhibitive function aimed at the performance enhancement of the DSSCs. Cobalt complex redox couple electrolytes have recently been used to obtain a high open-circuit voltage (V_oc) in dye-sensitised solar cells (DSSCs) because of the positively high redox potential of the electrolyte. However, in some cases, unexpectedly low V_oc was obtained because the fast back electron transfer reactions from the TiO₂ surface to the redox species, recombination, are occurred. To investigate the recombination suppressible function in dye structure, carbazole dyes with various structural features in each dye component, i.e., bulky appendage in donor group, and alkyl chain length in thiophene linker moiety, were studied. In the results, the bulkiness of the appendage group in the donor segment and shorter alkyl chains in the thiophene linker moiety increase V_oc with retard the recombination.