Molecular design of TPD-based organic A-π-D-π-A dyes for dye-sensitized solar cells

An interesitng class of organic A-π-D-π-A dyes based on an N,N,N′,N′-tetraphenylbenzidine(TPD) unit as donor was designed and synthesized for dye-sensitized solar cells(DSSCs). TPD-4-based DSSCs gave a short circuit photocurrent density(Jsc) of 16.67 mA/cm2, a open circuit voltage(Voc) of 0.635 V and a fill factor(ff) of 0.68, achieving a solar-to-electricity conversion efficiency(η) of 7.22% in preliminary tests. The N3-sensitized device gave an η value of 8.02% with a Jsc of 18.81 mA/cm2, a Voc of 0.630 V and an ff of 0.68 under the same conditions. The incident photo-to-current efficiency(IPCE) values above 70% observed in a range of 460 to 600 nm with a maximum value of 80% at 500 nm indicate that the TPD-4-based DSSC shows a high performance. Under the same conditions, the DSSC based on N3 provided the IPCE values above 70% in a range of 490 to 580 nm with a maximum value of 76% at 500 nm. Both further optimization of the device processing and structural modification of these dyes are anticipated to make the device give even better performances.