Impact of π-conjugation configurations on the photovoltaic performance of the quinoxaline-based organic dyes

Three novel quinoxaline-based donor-π-acceptor type organic dyes were synthesized and explored as sensitizers in dye-sensitized solar cells (DSSCs). The impacts of various π-conjugation configurations which contain different quinoxaline derivatives on the absorption properties , electrochemical properties and photovoltaic performances , as well as theoretical calculations have been investigated systematically. The photovoltaic performances of these dyes were found to be highly relevant to the π-conjugated configurations. In particular, the DSSC based on the dye with 2,3-dioctylquinoxaline as the spacer exhibited the highest efficiency of 8.20% with a short-circuit photocurrent density of 17.83 mA cm −2 , an open-circuit photovoltage of 0.71 V, and a fill factor of 0.65, under standard global AM 1.5G solar light condition. However, the DSSC based on the dye with a more conjugated dithieno [2,3- a :3′,2′- c ]phenazine core as the spacer exhibited a lower efficiency due to serious intermolecular aggregation. When the intermolecular aggregation is inhibited, the efficiency can be improved greatly. The results confirm that the configuration of the π-conjugation of the dyes should be considered for the improvement of the photovoltaic performance.