Design,Synthesis And Properties Of Polymer Photovoltaic Materials Based On Thiophenethiophene Side Chain Engineering

In recent years,the survival of fossil energy in human society has been exhausted,environmental pollution has become increasingly serious,and energy consumption with high energy consumption and low energy efficiency cannot meet the needs of future development.Therefore,it is urgent to develop green,clean and sustainable new energy sources.Organic solar cells（OSCs）have gradually become a research hotspot in the energy field due to their advantages of green cleaning,no geographical restrictions,easy availability of raw materials,flexibility and lightweight,and large-area printing preparation.The development of classical polymer photoactive materials was systematically summarized in this dissertation.For OPV suffered from some key scientific problems,such as expensive,tedious preparation,low photoelectric conversion efficiency,few species,as well as lack of acceptor unit,herein,some novel wide bandgap polymers based on thienothiophene（TT）as acceptor unit modified by side chain engineering,thiophene derivative and BDTT as donor,were designed and synthesized for organic photovoltaic materials.The molecular structures of these polymeric monomers were fully characterized.Their opto-physical,electrochemical,thermal properties,charge mobilities and photovoltaic performance the obtained polymers were well investigated alonged with their theoretical calculations.The effects of molecular structure and functional substitution of side chains on the photoelectric properties of D-A type wide band gap polymer donor materials were investigated.The main research contents of this thesis are as follows:1)A series of D-A type wide band gap polythiophene derivatives based on the2,6-position ester-substituted thiophene（DETT）acceptor with dithiophene,（E）-1,2-di（thiophen-2-yl）ethylene and thiophene as donor units,were designed and synthesized.The effects of the donor unit for photophysical electrochemical and photovoltaic properties of their resulting molecules were systematically studied.The effect of polymer configuration,molecular planarity and active layer morphology on their photovoltaic performance were systematically investigated.It was found that PDETT-TVT-HD/PC71BM based device exhibited a higher photoelectric conversion efficiency（PCE）of 6.62%with an open circuit voltage（Voc）of 0.89 V,short-circuit current(J_sc)of 10.93 mA cm^-2 and fill factor（FF）of 67.88%.2)A series of D-A type wide bandgap polythiophene derivatives based on the2,6-position ester-based dodecyl group substituted thiophene（DETT）as acceptors,bithiophene,（E）-1,2-di（thiophen-2-yl）ethylene,thiophene and 2,6-position alkylthio substituted thiophene（TTS）as donors,were designed and synthesized.The length and quantity of alkyl chain in polymer backbone were systematically studied,which have effect on molecular planarity,active layer morphology and photovoltaic performance.Among them,the absorption spectrum of PDETT-TVT-BO has obvious red shifted,the introduction of alkylthio group reduces the HOMO level of its corresponding polymer.The PDETT-TVT-BO/PC71BM based device exhibited a higher PCE of 7.05%,V_oc of 0.90 V,J_sc of 12.96 mA cm^-2 and FF of 66.34%.3)A series of D-A type wide band gap polymer donor materials based on DETT and 2,6-position carbonylalkyl substituted thiophene（DCTT）acceptor units,bithiophene and BDTTS as donor units,were designed and synthesized.The pacts of the different electron-withdrawing side groups and different donor unit the photophysical electrochemical and photovoltaic properties of their resulting molecules were systematically studied.The PDETT-2T blended with non-fullerene acceptor IT-4F presented a PCE of 5.92%,V_oc of 0.87 V,J_sc of 15.45 mA cm^-2 and FF of 44%.