Preparation And Study On Polymer Donors Based On Benzodithiophene And Symmetric/Asymmetric ? Bridge Structure

As the effective technologies for the utilization of solar energy,polymer solar cells(PSCs)have attracted much attention because of their merits on low cost,flexibility,semitransparency and so on.Up to now,most of successful electron donor-electron acceptor(D-A)type polymer donors possess symmetric backbone,and polymer donors with asymmetric structures are rarely studied.In this thesis,? bridges with different length were introduced between benzodithiophene(BDT,D unit)and different A units symmetrically or asymmetrically.This thesis is divided into the following works:1)Tailorable thiophenes with different length were introduced between 2D BDTs and benzodithiophene-4,8-dione(BDD)symmetrically or asymmetrically.Together with the halogen substituent(fluorine or chlorine)on BDT unit,four polymer donors were designed and synthesized in parallel.Of all,PTB2T-F and PTB2T-Cl containing the asymmetric ?bridge of thiophene and hexyl-bithiophene exhibited superior photovoltaic performance to PTB2T-F and PTB2T-Cl with the symmetric ? bridge of hexyl-bithiophene.The PSCs based on inverted and conventional structures are utilized for the objective valuation of polymer donors.It is worth noting that the PTB2T-F:IT-4F obtained 10.79% PCE without additives.2)? bridges with different length were introduced between 2D BDTs and difluorobenzothiadiazole(FBT)symmetrically or asymmetrically vis Stille coupling and bromination reaction.Moreover,with different halogen atoms,four new polymer donors,PDFBF,PDFBCl,PDFBF-TT and PDFBCl-TT,were designed and synthesized in parallel.In terms of light absorption,polymer planarity and the excitons dissociation efficiency,PDFBF and PDFBCl with a symmetric ? bridge were superior to PDFBF-TT and PDFBClTT with asymmetric ? bridge.As expected,device based on PDFBF and PDFBCl presented higher PCE than those based on PDFBF-TT and PDFBCl-TT.Especially PDFBCl,the conventional device based on PDFBCl:IT-4F obtained a PCE of 10.91% without additives.3)Tailorable thiophenes with different length were introduced between 1D BDTs and benzodithiophene-4,8-dione(BDD)symmetrically or asymmetrically,the resulting PTBOD and P2TB-OD,with asymmetric and symmetric ? bridge were synthesized and studied.Morphology analysis showed that PTB-OD:ITIC active layer had a better miscibility compared with P2TB-OD:ITIC active layer.Therefore,device based on P2TB-OD with symmetric ? bridge displayed a poor PCE of 2.35%,while the devices based on PTBOD:ITIC exhibited a moderate PCE of 5.80%.