Study On Synthesis And Photovoltaic Performances Of Polymer Donor Materials Based On Benzodithiophene And Benzodithiophenedione

Polymer solar cells（PSCs）have attracted tremendous attention in all over the world,due to their advantages of solution process,low cost,lightweight,and potential for the fabrication of large-area flexible devices.However,the low power conversion efficiency（PCE）restricts the commercial development of PSCs currently.To improve the PCE of PSCs,thisthesisusesbenzodithiophene（BDT）asdonorunitand benzo[1,2-c:4,5-c′]dithiophene-4,8-dione（BDD）as acceptor unit to synthesize copolymers,in which selenophene unit asπ-conjugated spacer was incorporated into the polymer backbone.Fullerene derivative and non-fullerene derivative were selected to fabricate the photovoltaic devices,meanwhile,the photovoltaic performances were studied systematically.The main research contents of this thesis are listed below:1.A copolymer based on m-alkoxyphenyl substituted benzodithiophene（BDT-m-OP）as donor unit and benzo[1,2-c:4,5-c′]dithiophene-4,8-dione（BDD）as acceptor unit was designed and synthesized,in which selenophene unit asπ-conjugated spacer was incorporated into the polymer backbone to broaden the absorption spectrum,enhance the charge transport properties.Compared to PBPD-Th with thiophene asπ-conjugated spacer,PBPD-Se exhibits an evidently extended absorption spectrum and an enhanced hole mobility with a slightly raised HOMO energy level.PBPD-Se:PC₇₁BM-based PSCs exhibit a PCE of 9.8%.2.We have optimized the non-fullerene PSCs with broad band-gap based polymer PBPD-Th as donor.PBPD-Th shows a strong absorption in the short wavelength of 300-650 nm with a band-gap of 1.91 eV,which is complementary with that of ITIC（1.55 eV）.Moreover,PBPD-Th possesses a deeper HOMO level（-5.42 eV）,which is beneficial to obtain a high open-circuit voltage（1.01 V）in PSCs.The optimized PBPD-Th:ITIC PSCs achieved a high PCE of 10.8%.