Design,synthesis Of D-A Type Polymers And Photovoltaic Performance Of Polymer Solar Cells

During the past few decades,polymer solar cells(PSCs)using bulk heterojunction(BHJ)active layer have been widely investigated because of their advantages of low cost,light weight,solution processable and mechanical flexibility.BHJ active layer that consisting of donor and acceptor dominants the power conversion efficiency(PCE)of PSCs.In this dissertation,a series of polymer with benzodithiophene(BDT)and oligothiophene as the electron-donating unit,isoindigo,benzodithiophene-4,8-dione(BDD),difluorobenzothiazole(FBT)and naphthalene diimide(NDI)as the electron-accepting unit had been synthesized.Nuclear magnetic resonance(NMR)was employed to characterise the chemical structure.Physical,optical and electrical parameters were measured by gel permeation chromatography(GPC),thermogravimetric analysis(TGA),UV-vis absorption spectrum and cyclic voltammetry(CV).Photovoltaic performances of these polymers were investigatedfrom the PSCs.This dissertation is divided into the following five parts:(1)Two polymers with alkyl and thioalkyl side chain were synthezied via Stille polymerization.When mixed with PC₇₁BM,the devices based on PBCID and PBSID exhibited the PCE of 0.71%and 0.64%,respectively.(2)Three polymers were synthezied based on benzodithiophene-4,8-dione.With PC₇₁BM as acceptor,PDTB,PDFTB and PBSB based devices yielded the PCE of 3.81%,4.39%and 5.04%,respectively.The results suggest that introducing fluoro atom into the polymer backbone or copolymerizating with BDT unit can enhance the PCE of the device.(3)In order to study the spacer in the polymer backbone,a series of polymers were synthesized and studied,in which different number of thiophene with and without alkyl side chains were incorporated into the backbone of BDT-FBT D-A alternating copolymer.With an alkyl thiophone and a bare thiophone as the spacer,PBTTF-H showed the highest backbone planarity among the three.The corresponding device exhibited the highest PCE of 6.80%when processed by environment friendly non-halogenated solvent.(4)Conjugated polymer POBDFBT was synthesized with the high planar backbone,in which alkoxy side chain was introduced on the BDT unit.With ITIC and PC₇₁BM as the acceptors,the ternary devices exhibited broaden absorption range compared with the binary ones,leading to a higher J_SC and an promising PCE of 7.91%?(5)Two random polymers based on bithiophene and NDI were synthesized as the acceptor.With J51 as the donor,PNT10 exhibited higher electron mobility and balanced hole/electron mobilities than PNS10.The devices based on PNT10 and PNS10 exhibited the PCE of 5.07%and 4.47%,respectively.