Quinoxaline-based organic dyes for efficient dye-sensitized solar cells: Effect of different electron-withdrawing auxiliary acceptors on the solar cell performance

Abstract

Three novel metal-free organic dyes IT, IPT and IQT, containing a dipentyldithieno[3,2-f:2′,3′-h]quinoxaline (DPQ) unit as the π-bridge were synthesized and the impacts of the auxiliary acceptors on the photovoltaic performances were studied. IQT with 2,3-dipentylquinoxaline as the auxiliary acceptor exhibited the highest efficiency of 7.98%, with a short-circuit photocurrent density of 16.87 mA cm−2, an open-circuit photovoltage of 0.71 V, and a fill factor of 0.67, under standard global AM 1.5G solar light condition. IPT with the strongest electron-withdrawing group (2,3-dipentylpyridopyrazine) as the auxiliary acceptor could red-shift the absorption range, but showed the weakest performance, which might be due to the electron trap of the 2,3-dipentylpyridopyrazine unit. The results show that incorporating auxiliary acceptor with moderate electron-deficient ability can extend the absorption range and adjust the molecular orbital energy levels, improving the photovoltaic performance.