Synthesis And Photovoltaic Properties Of Conjugated Polymer Base On Different ? Bridges And Difluorobithiophene

In the process of rapid socio-economic development,energy has always been a crucial issue for everyone.With the increasing demand for energy,it is imperative to develop new energy sources and optimize the energy structure.Solar energy is widely concerned because of its clean,environment friendly and other characteristics.In such a background,organic solar cells emerge as the times require.Polymer solar cells(PSCs)are widely concerned by researchers because of their low cost,easy manufacture and mechanical flexibility.In recent years,the power conversion efficiency(PCE)of bulk heterojunction polymer solar cells(BHJ PSCs)have improved significantly and those of single-junction BHJ PSCs have gradually exceeded 13%.However,there are still many problems for the commercialization of organic solar cells.Therefore,researchers are still struggling as early as possible commercialization of organic solar cells.Here,we designed and synthesized a series of photo-sensitive polymer materials and the structures of the as-synthesized copolymer were confirmed by 1H-NMR.The thermal,photophysical,electrochemical properties of the copolymers have been investigated by thermal gravimetric analyzer(TGA),UV-visible spectra(UV-vis),cyclic voltammetry(CV).Subsequently,the photovoltaic performance of BHJ PSCs devices based on the synthetic polymers have been tested and characterized.The main contents of this dissertation are as follows:1.We designed and synthesized two random copolymers(PI and P2)containing BDT donor unit and BT acceptor unit with furan and thiophene as?-bridges by Pd-catalyzed Stille-coupling reaction.Two copolymers possess good solubility and thermal stability.The ?-bridge units significantly influence the molecular architecture and consequently impact on the optoelectronic properties of the copolymers.The absorption peaks of the P1 and P2 solution red-shifted from 516 to 568 nm and the band gaps of the two polymers were tuned from 1.62 to 1.66 eV.The PCE of the PSCs based on P1 and P2 as donor and PC61BM as acceptor reached 0.35%and 1.21%,respectively.Obviously,the PCE of the PSC based on funan bridged polymer P2 is much higher than that of the thiophene bridged polymer P1.The study results indicate that funan bridge is propitious to enhance the photovoltaic properties of D-?-A copolymers.The results provide new insights toward the design of high performance photovoltaic materials.2.A series of DFDT-DPP-TPD random terpolymers containing two different electron-deficient units(DPP and TPD)were synthesized.The terpolymers possess a strong absorption from 400 to 900 nm.Due to the introduction of the second acceptor of DPP unit with strong electron-withdrawing ability in the conjugated backbone,polymers exhibited broad absorption and deep lying HOMO energy level as the increasing of DPP unit.Under optimized conditions,polymer solar cells(PSCs)based on P6 exhibits a PCE of 3.80%with a Voc of 0.73 V,Jsc of 7.87 mA cm-2 and FF of 66.0%.The study results showed that by incorporating appropriate acceptor unit into the random conjugated polymer as a second acceptor unit is an effective strategy to broaden the absorption,finely tune energy level of the original copolymer and improve photovoltaic performance of polymers.