Synthesis And Properties Of Organic Solar Cell Materials Based On TPTI

In recent years,organic solar cells?OSCs?have made rapid progress,and the power conversion efficiency?PCE?has reached 17%.Among them,photovoltaic donor materials are one of the focus in this field.Thieno[2',3':5,6]pyrido[3,4-g]thieno[3,2-c]-isoquinoline-5,11?4H,10H?-dione?TPTI?is a pentacyclic aromatic lactam acceptor unit.In this thesis,a series of D-A,D-A₁-D-A₂ type conjugated polymers and A₂-?-A₁-?-A₂ type conjugated organic small molecule donor material based on TPTI were designed and synthesized.The thermal stability,photophysical,electrochemical and photovoltaic properties of these target polymers and small molecules were studied in detail.The relationship between molecular structure and optoelectronic properties was investigated.The main contents are as follows:1.Three D-A type conjugated polymers?CP1,CP2 and CP3? based on TPTI unit were designed and synthesized by copolymerizing with benzodithiophene?BDT?unit with different side chains.The effects of different side chains?oxyalkyl,alkylthiophene and thioalkylthiophene?in BDT on optoelectric properties of the resulting copolymers were systematically studied.Results showed that the introduction of the alkylthiophene and thioalkylthiophene side chains can reduce the HOMO/LUMO energy levels and broaden the absorption spectra of the polymers,thus resulting the increase of open circuit-voltage(V_oc and short circuit-current(J_sc.At the same time,the introduction of conjugated side chains can extend the effective conjugation degree of BDT molecules,which is beneficial to promoting the separation of excitons and increasing the efficiency of charge transport.OSCs based on these polymers with PC₇₁ BM as acceptor exhibited PCEs of 5.01%,5.03% and 5.35%,respectively.OSCs based on these polymers with ITIC as acceptor exhibited PCEs of 1.84%,1.58% and 1.66%,respectively.2.Two D-A₁-D-A₂ type conjugated polymers?CP4 and CP5? based on TPTI unit were designed and synthesized.Among them,thiophene/alkylthiophene is used as electron-donating unit?D?,TPTI unit?A₁? and benzodithiophenedione?BDD? and fluorobenzothiadiazole?FBT? are used as electron-withdrawing copolymer units?A2?.The effect of different electron-withdrawing units on the photoelectric properties of the copolymer was investigated.The results showed that the two polymers have wide spectral absorption?300-800nm?,compared with CP4,CP5 is red-shifted.This is because FBT has stronger electron-withdrawing ability.Because the polymer structural unit contains two electron-withdrawing units?A₁ and A₂?,both polymers have a very low HOMO energy level?^-5.6 eV?.OSCs based on these polymers with PC₇₁BM as acceptor exhibited PCEs of 3.53% and 6.2%,respectively.OSCs based on these polymers with ITIC as acceptor exhibited PCEs of 2.73% and 6.01%,respectively.3.Four A₂-?-A₁-?-A₂ type organic small molecule?CS6?CS7?CS8 and CS9? based on TPTI unit were designed and synthesized.Which used TPTI as the electron-withdrawing core A₁,used 3-hexylthiophene or 3,3"-dioctyl-[2,2':5',2"-trithiophene]as?bridge.The terminal electron-withdrawing unit A₂ are 1,3-indanedione or 3-ethyl bypassed tannin.The effects of different?bridges and electron-withdrawing ends on the photoelectric properties of these small molecules were investigated.The results showed that four small molecules have good thermal stability,wide and strong absorption properties.CS6 and CS7 have good solubility,while the solubility of CS8 and CS9 are poor.Because the indone has stronger electron-withdrawing ability than the tannin,which makes the small molecule with indone-based red-shifted compared to the tannin-based,HOMO energy level is lower.The V_oc of this series of small molecules are relatively high,the open circuit voltage of CS6 reaches 1.04V.OSCs based on CS6 with PC₇₁ BM as acceptor exhibited PCEs of 3.82%.