A new organic dye bearing aldehyde electron-withdrawing group for dye-sensitized solar cell

A new metal-free dye (I) with a diketopyrrolopyrrole (DPP) core was synthesized, in which triphenylamine was used as electron donor, thiophene units as the π-conjugated bridge, aldehyde units as electron acceptor. The corresponding dye II containing carboxy group as the electron-withdrawing acceptor for the purpose of comparison was also synthesized. The absorption spectra, electrochemical and photovoltaic properties of I and II were extensively investigated. Electrochemical measurements data indicate that the tuning of HOMO and LUMO energy levels can be conveniently accomplished by alternating electron acceptor. The short-circuit photocurrent density and conversion efficiency of solar cell based on aldehyde-containing dye is more dominant than that bear a carboxy group as the electron withdrawing anchoring group. The new sensitizer I exhibited a photovoltaic performance: a short-circuit photocurrent density (Jsc) of 6.07 mA cm−2, an open-circuit photovoltage (Voc) of 568 mV, and a fill factor (FF) of 0.66, corresponding to an overall conversion efficiency of 2.27% under standard global AM 1.5 solar light condition. This work suggests that aldehyde units as new type of electron withdrawing anchoring group are promising candidates for improvement of the performance of DSSCs.

► Aldhyde moiety is firstly used as the electron-withdrawing anchoring group in DSSCs.
► The LUMO level of aldehyde dye is more negative than that of carboxylic sensitizer.
► The driving force of electron injection of sensitizer bearing aldehyde was improved.
► Aldhyde-based DSSCs exhibited better conversion efficiency.