Synthesis And Properties Of D-D-π-A Sensitizers Containing Triphenylamine Units

Dye-sensitized solar cell（DSSC）was developed by professor Gr?tzel of the Swiss federal Institute of Technology in Lausanne.In recent years,the DSSC has gained much attention due to its low productional costs and efficient fabrication.Dye sensitizer,taking the role of absorbing sunlight,is one of most important parts of DSSC.The structure of dye sensitizer plays a decisive influence on the battery performance.Thus,to optimize the dye structure is of significant for improving the photoelectric performance of DSSC.Considering the D-π-A structure of most organic dyes,in this work,we increase an additional triphenylamine on the photosensitive D1 dye as a second electron-donor to form a new dye of D-D-π-A structure and investigate the effect of second electron-donor on dye performance.In order to investigate the influence of different bridging bonds on the performance of dyes,ethylene,butadiene and p-phenylene diene were used as bridging bonds to connect two electron donors,respectively.Moreover,we further investigate the effect of different alkoxy groups for the performance of dye properties through introducing methoxy or hexyloxy groups on the second electron-donor.All the structure of D2～D7 dyes are D-D-π-A calculated by quantum chemical method.The reaction of D1～D7 dyes synthetization involves the Vilsmeier reaction,Stille coupling reaction and Knoevenagel condensation reaction.And the D1～D7 dyes and their intermediates were corresponding structure identified by IR,¹HNMR,¹³CNMR and HRMS.The photophysical properties of the seven dyes show that increasing the second-electron donor in the dye molecular structure can lead toward shift of the absorption peak,which is from 477 to 506 nm（the maximum absorption peaks）of the six new dyes.Compared with the reference dye D1（482nm）,the D3～D7 dyes have a red shift ranging from 7 to 24 nm.The molar extinction coefficients of the six novel D-D-π-A structure dyes were 29500～38500 M^-1·cm^-1,which is 1.9～2.4 times of the reference dye D1,indicating that the spectral absorption capacity of the dye is greatly improved.Testing the DSSC of seven dyes shows that the photoelectric conversion efficiency of D2～D7 is from 5.48 to 6.86%,which is higher than the reference dye D1（5.33%）.In particular,the photoelectric conversion efficiency of the photosensitive dye D6 was 6.86%,which was1.3 times than that of the reference D1 dye.The maximum value wavelength of the Incident monochromatic photon-to-electron conversion efficiency（IPCE）of the D2～D7dyes is 431～504 nm,having red shift of 44～117 nm compared with dye D1,indicating that the addition of second-electron donor in the dye structure can effectively improve the battery performance.