Design,Synthesis,and Photovoltaic Application Of Conjugated Polymers Based On Regioisomerically-pure 1,7-Dibromo Perylene Diimides

All-polymer solar cells(all-PSCs)are focused recently,because polymeric semiconductors exhibit excellent flexibility,film forming ability,mechanical strength,and charge transport.Compared with excellent donor materials,acceptor counterparts with poor performance lag behind.Perylene diimides(PDIs)and naphthalene diimides(NDIs)are two excellent acceptor building blocks as they are with high stability,high electron acceptability and high carrier mobility.Since dibromo perylene diimides(DBPDIs)contain two isomers that are difficult to separate,which affected the performance and application of the PDI polymers,a series of regioisomerically-pure 1,7-dibromo perylene diimides polymers were designed and synthesized.The following two arts were involved in this work.1.Design,synthesis,and photovoltaic application of single-strand and ladder-type polymeric acceptors based on regioisomerically-pure 1,7-dibromo perylene diimides.Single-strand polymers(PrPDIT)were synthesized by the polymerization of regioisomerically-pure 1,7-dibromo-PDIs(1,7-DBPDIs)and thiophene.Furthermore,ladder-type polymers(FPrPDIT)were obtained by the highly efficient photo-induced cyclization of polymers PrPDIT.The effects of isomers and molecular weight on the absorption,electrochemistry,thermal stability,and photovoltaic application of polymers were studied.Pure 1,7-DBPDIs lead to polymers with molecular weight distribution as low as 1.08.These polymers with strong absorption in 300-700 nm,low-lying lowest unoccupied molecular orbital(LUMO)energy levels around-4.0 eV and high thermal stability could be excellent electron acceptors.Regioisomerically-pure polymers demonstrate better photovoltaic performance than that of mixed ones.The highest power conversion efficiency(PCE)of all-polymer solar cells based on PrPDIT and FPrPDIT is up to 5.95%and 4.52%respectively.2.Design,synthesis and photovoltaic application of terpolymers based on naphthalene diimides and regioisomerically-pure 1,7-dibromo perylene diimides.The optical properties and electrochemical properties of NP-ED and NP-Th polymer were tuned via random incorporation of PDIs as coacceptor with NDI-Th.Four random ternary conjugated polymers were synthesized by Stille coupling reaction of thiophene blocks or 3,4-ethylenedioxythiophene blocks as donor blocks,NDI-Th and regioisomerically-pure perylene diimide(xPDI,x=10,30 mol%PDI)as mixed acceptors.All of them have a wide absorption range and near-infrared absorption.NP-ED1 has an absorption edge of 970 nm,which can more effectively utilize sunlight when matching with donor materials.The highest power conversion efficiency(PCE)of all-polymer solar cells based on NP-ED1 and NP-Thl is up to 0.59%and 3.98%respectively.