Synthesis Of Dithienosilole Based Conjugated Ploymers With High Open-circuit Voltages And Its Application In Organic Photovoltaic

Because of the energy crisis is becoming more and more serious, the research and application of solar energy have received much more attention. Polymer solar cells(PSCs) were considered to be one of promising candidates of the new energy technology due to their low-cost fabrication, light weight, as well as excellent compatibility with flexible substrates.. Nowadays, “quinoid” conjugated polymer with low band gap polymers, high hole mobility and other characteristics, had become the major materials used in polymer solar cells.In this thesis, serveral novel and unsymmetrical dithienosiloles(7,7-dimethyl-4,6-di(trimethylsilyl)-dithieno[2,3-b:3′,4′-d] siloles(DTSi)) with different functional groups were synthesized. Finally, these silole-based monomers were copolymerized with benzo[1,2-b:4,5-b′]dithiophene(BDT) unit via Stille polymerization and a series of silole-based “quinoid”conjugated polymers were synthesized with DTSi and reaction. Their photovoltaic properties were studied when used as the electron donor materials in polymer solar cells.The research work in this thesis was mainly composed of three parts:Part I. Synthesis and charactrization of DTSi-based quinoid-typed conjugated polymers with different electron withdrawing groupsThree new DTSi monomers were obtained by grafting different electron withdrawing groups at one end of the DTSi units and the corresponding quinoid polymers were synthesized via the Stille copolymerization of different DTSi units and BDT unit. The final polymers were characterized by 1H NMR,gel permeation chromatography(GPC), Uv-vis spectroscopy(Uv-vis) and cyclic voltammetry(CV).Finally, thepolymer solar cell devices were assembled with these polymers as the donor materials and PC71 BM as the acceptor. All of the devices exhibited high open-circuit voltages(Voc) over 1.00 V, which may originated by introducing the DTSi unit. Meanwhile, the device made from PDTSi BDT-1demonstrated a best PCE of 3.29 %, with an open-circuit voltage(Voc) of 1.07 V, a short-circuit current density(Jsc) of 7.53 m A/cm2, a fill factor(FF) of 40.74 %.Part Ⅱ. Synthesis and charactrization DTSi-based quinoid-typed conjugated polymers withdifferent alkyl chainsIn Part I, since the alkylacyl substituted DTSi displayed good performance, five monomers with different alkylacyl groups were desig4 ned and synthesized to study the alkyl chain effects on the properties of the polymers.The corresponding quinoid polymes were obtained via similar Stille polymerization and these materials were characterized by 1H NMR, GPC, Uv-vis and CV. The photovoltaic devices were fabricated from the polymers with similar molecular weights and the results indicated that these polymers still exhibited high Voc over 1.00 V. While PDTSi BDT-5,which was modified with the 3,7-dimethyloctyl chain, demonstrated a best performance PCE of 2.66 %, with a Voc of 1.01 V, a Jsc of 6.71 m A/cm2, a FF of39.17 %.Part Ⅲ. Synthesis and charactrization of DTSi-based ternary quinoid-typed conjugated polymersTernary polymer based solar cells was another hot research topics at present. To improve the absorption spectra of PDTSi BDT-1, a series of random ternary polymers were synthesized with DTSi units and BDT unit via Stille polymerization reaction according to different ratios of1-(4,6-dibromo-7,7-dimethyl-dithieno[2,3-b:3’,4’-d]silole-2-yl)nonan-1-one(7) and(Z)-3-(4,6-dibromo-7,7-dimethyl-dithieno[2,3-b:3’,4’-d]silole-2-yl)-2-isocyanoacrylonitrile(11)(1 : 0, 3 : 1,1 : 1, 3 : 1 and 0 : 1) were used during the copolymerization. Finally, the 1H NMR confirmed that ratio of the two different DTSi monomers was consistent with their feed ratios. The final polymers were characterized by GPC, Uv-vis and CV. The photovoltaic devices fabricated from the polymers demonstrated that these polymers still kept high Voc and their absorption spectrum could be effectively adjusted by tuning the ratio of the DTSi monomers.