Based On Two-dimensional Structure Of Benzene And Thiophene Electron Donor Cell Polymer Solar Cell Materials

Comparing with the traditional solar cells based on silicon, polymer solar cells show the advantages of low cost, low pollution, feasible mass production with solution processing techniques for flexible devices. Now, low band gap polymers with the D-A structure of electron donor unit and electron acceptor unit have become the major materials used in polymer solar cells, while the unit of two-dimensional benzodithiophene (BDT-T) has been proved to be an excellent electron donor unit. So, in this thesis we chose BDT-T unit as the donor unit and have developed the BDT-T based polymers by the use of thiozolothiozole (TTz), dithienylylbenzothiadiazole (DTBT) and pyrrolopyrrole-1,4-dione (DPP) acceptor units. Altogether four new polymer materials have synthesized through Stille com-polyerization with the modified acceptor units and donor unit. We have characterized the properties of the materials and the device characterization has also been carried out. The results are as follows:The energy level distribution of the polymer constituted of DPP unit and BDT-T unit was close to the ideal state and this polymer shows a lower optical band gap and a broader range of absorbtion, compared with the polymers composed of TTz unit or DTBT unit with BDT-T unit.Alkoxy substituent of TTz unit can raise the HOMO level of the polymer, thereby reducing the Voc of the device. However, the alkoxy substituent of DTBT unit can low the HOMO level. By replacing the thiophene group with thienothiophene group, the absorption intensity of the polymer in short-wavelength region was significantly increased, without changing the distribution of energy level and the absorption in long-wavelength region.In this thesis, we have got preliminary device testing on the polymer constituted of TTz unit and BDT-T unit, the power conversation efficiency was1.53%with the device structure of ITO/PEDOT:PSS/polymer:PC71BM(2:1)/PFN/Al. The low Jsc value was corresponded with the low molecular weight of the polymer and the processing technique of the device. The power conversation efficiency can be further improved though improving polymerization conditions and optimizing device processing. The device testing of the remaining polymer is underway now.