Design, Synthesis And Characterization Of Novel Low Bandgap Conjugated Polymers Forphotovoltaic Applications

In this thesis, an alternating copolymer was successfully synthesized via Stille cross-coupling polymerization by choosing 3,4-Ethylenedioxy-thiophene (EDOT) as an electron donor and 3,4-Bis(4'-dodecylphenyl)-2,5-bis(4'-bromophenyl)cyclopentadienone as an electron acceptor. The target polymer poly(bis(4'-dodecylphenyl)-diphenylcyclopentadienone-alt-3,4-ethylenedioxythiophen) (DPPD) was characterized using 1H NMR, 13C NMR and GPC analysis. It has higher molecular weight than some similar polymers. Thermal, optical and electrochemical properties of DPPD were characterized. The results demonstrate that the copolymer DPPD has good thermal stability with thermal decomposition temperature at 376.6℃. The copolymer DPPD has a broad absorption from 500 nm to 750 nm and its optical band gap was estimated to be 1.55 eV. The electron affinities (EA, LUMO level) of 3.59 eV and the ionization potential (IP, HOMO level) values of 5.14 eV was obtained from the cyclic voltammetry curve. A bulk heterojunction device with the new copolymer and [6. 6]-phenyl-C61 butyric acid methyl ester (PC60BM) as the activity layer was fabricated. It shows an open circuit voltage of 0.63 V, a short circuit current of 0.45 mA/cm2, the fill factor of 0.28 and the power conversion efficiency of 0.08%.