Synthesis And Optoelectronic Properties Of Organic Electron-Transporting Materials Containing Naphthaleneimide Or Perylenediimide Derivatives

Aromatic imides and their derivatives have been widely used as the promising building blocks for the development of novel organic/polymeric electron-transporting materials?ETMs?.In this dissertation,two diarylcyclopentadienone-fused naphthaleneimide?NI?building-blocks and their low band-gap donor-receptor?D-A?polymers are synthesized and used as the ETMs.In addition,two isomeric benzodithiophene-fused PDI small molecules are also developed as the ETMs.The relationship between material structure and optoelectronic property has been detailedly discussed.The main research contents are as follows.1)In this section,two novel aromatic imides,diarylcyclopentadienone-fused naphthaleneimides?BCPONI-2Br and TCPONI-2Br?,are designed and synthesized by performing Knoevenagel condensation coupling reactions between ketone-containing NI intermidate and 1,3-bis?4-bromophenyl?-2-propanone or1,3-bis?5-bromo thiophenyl?-2-propanone.It is found that both BCPONI-2Br and TCPONI-2Br acceptors possess broad absorption bands,low optical band-gap,and low-lying LUMO energy levels.On the basis of both building blocks,we develop six low band-gap D-A copolymers,including phenyl-containing polymers?P1-P3?and thienyl-containing polymers?P4-P6?.The absorption,optical band-gap(E_g^opt),and HOMO/LUMO energy level of the polymers are fine-tuned by the variations of donors?carbazole,benzodithiophene,and dithienopyrrole?and?-conjugation linkers?thiophene and benzene?.The main research results are as follows:1)Compared with the phenyl-containing polymers?P1-P3?,the thienyl-containing polymers?P4-P6?exhibit extended absorption bands and deeper LUMO energy levels due to more electron-rich thiophene and more planar?-conjugation skeleton;2)With increasing electron-donating ability of the donor units,two type of polymers exhibit extended absorption bands,reduced optical band-gap,and upshifted HOMO levels.For the TCPONI-containing polymer?P6?,an ultralow E_g^opt of 0.81 eV is observed.Under ambient condition,P5 exhibits a moderately high hole mobility of 0.02 cm² V^-11 s^-1 in bottom-gate field-effect transistors?FETs?,while a typical ambipolar transport behavior can be observed in top-gate FETs,achieving the highest hole and electron mobilities of 4.11×10^–3 and 5.15×10^–4 cm² V^–11 s^–1,respectively.2)In this section,we report the design and synthsis of two isomeric benzodithiophene-fused PDI acceptors,BPDI-1 and BPDI-2,in which the isomeric benzodithiophene donor cores like benzo[2,1-b:3,4-b']dithiophene?BDP?and benzo[1,2-b:4,3-b']dithiophene?BdT?are fused at the bay-position of PDI units via photo-induced ring-closure reaction.The effect of structural isomerism on the molecular geometry,absorption,energy level,film morphology as well as photovoltaic performance are discussed.It is found that a almost linear conjugation and very small backbone distortion are observed for BDP-containing BPDI-1 acceptor,while the BdT-containing BPDI-2 shows a non-linear conjugation with a highly twisted skeleton.Such a unique geometry plays a key role in reducing molecule aggregation.Compared with BPDI-1,BPDI-2 exhibits extended absorption bands and enhanced electron-accepting ability,indicating BPDI-2 would be a promising electron-transport material for non-fullerene solar cells.Under the illumination AM1.5G,100 mW cm^–2,non-fullerene solar cells based on blends of PTB7-Th/PBPDI-2exhibit the highest power conversion efficiency?PCE?of 4.44%,higher than that of PTB7-Th/PBPDI-1 based solar cells?2.98%?.