Synthesis And Photovoltaic Properties Of Quinoxaline D-A-?-A Organic Dyes

Dye-sensitized solar cells(DSSCs)represent a class of low-cost photovoltaic technologies with potential of low cost,light weight,and good flexibility relative to traditional solid-state semiconductor devices and have received considerable attention recently.One of the crucial components of DSSCs is the photo-sensitizer.Compared to D-?-A structure,the D-A-?-A structure tends to extend the absorption spectrum,distinctly improve the light-harvesting ability,adjust the HOMO and LUMO energy levels,narrow the band gaps,contributing to effectively improve the efficiency of power conversion.To explore the effect of an electron-deficient quinoxaline moity and its relative linkage position on the performance of DSSCs,We report herein the design and synthesis of three organic sensitizers(HWD11,HWD12,HWD13)imparted with an electron-deficient quinoxaline derivatives in the framework of ?-conjugated spacer and to link the triphenylamine electron donor and cyanoacrylic acceptor,with furyl,thienyl,phenyl units as ?-conjugated spacer,respectively.All the dyes and relative intermediates have been fully characterized by nuclear magnetic resonance(1H NMR and 13C NMR)spectroscopy,High Resolution Mass Spectrometry(HRMS),etc.The optical and electrochemical properties and theoretical studies of these dyes were described indetail and photovoltaic performances of DSSCs sensitized by these dyes were also investigated.The results showed that HWD11(with furyl unit)and HWD12(with thienyl unit)exhibited broader absorption spectrum and stronger light-harvesting ability,compared to HWD13(with phenyl unit).At the same time,the J-aggregation of a dye on TiO2 surface results in the red-shift of absorption band.Redox of ground and excited states of dyes match well with that of I3-/I-and TiO2 conduction band,respectively.The DSSCs based on dye HWDs exhibited good performances:the short current density of 9.39 mA/cm2,7.84 mA/cm2,7.18 mA/cm2,respectively;the open circuit voltage of 0.69 V,0.66 V,0.71 V,respectively;the power conversion efficiency of 4.68%,3.53%,3.72%,respectively.It was found that the cell based on HWD11 has the best photovoltaic properties,which was attributed to greater dye loading on TiAO2 and higher short-circuit photocurrent density.In order to avoid the dye aggregation,CDCA was added to increase the I-values of HWDs-based DSSCs.As a result,all the JSC values increased to some extend.Finally,HWD11/CDCA-based DSSCs showed the highest ?(4.76%).