Synthesis And Optoelectronic Properties Of Conjugated Polymers Based On Dithienocoronene Diimide And Modified Benzo[1,2-b:4,5-b’]dithiophene

The D-A conjugated polymers of perylene diimide derivatives(PDIs) had an easy processability, the feasibility to tune the highest occupied molecular orbital(HOMO) and the lowest unoccupied molecular orbital(LUMO) energy levels, a abundant electron mobility, a wide absorption of maximizing the solar harvesting in the visible range and the correct aggregation properties in the bulk heterojunction(BHJ) active layer, which had drawn considerable attention of domestic and foreign scholars owing to their ability of multifaceted applications in the fields of organic thin-film transistors(OTFTs), and polymer solar cells(PSCs) etc.By computer simulating, molecular geometries of the target polymer was designed and made related calculations. According to theoretical calculations, P(BDT-PDI) and P(BDT-DTPDI) have significant polymer backbone torsion(41.44° and 39.64°), P(BDT-DTCDI) has an highly coplanar backbone with negligible angle. P(BDT-CDPDI) should have a high degree of regioregularity in a polymeric backbone and strong π-π stacking capability.Perylene diimide(PDI), dithienyl-perylene diimide(DTPDI) and dithienocoronene diimide(DTCDI) were synthesized from perylene tetracarboxylic dianhydride(PTCDA). Benzo[1,2-b:4,5-b’]dithiophene(BDT) was chose as the electron-donating monomer and PDI, DTPDI and DTCDI were chose as electron-accepting monomers for synthesizing the conjugated polymer P(BDT-PDI), P(BDT-DTPDI) and P(BDT-DTCDI) by Stille coupling reaction. The structre of three conjugated polymers were characterized via nuclear magnetic resonance(NMR) and elemental analysis(EA). The thermal properties, electrochemical properties, optical properties and film properties of three conjugated polymers were investigated by the thermal gravimetric analysis(TGA), cyclic voltammetry(CV), UV-visible spectrophotometer(UV-vis), fluorescent(FL) and atomic force microscopy(AFM).The results showed that P(BDT-PDI), P(BDT-DTPDI) and P(BDT-DTCDI) all exhibited very good thermal stability with their 10% weight-loss temperatures(Td) at 462 ℃, 468 ℃ and 470 ℃ under N2 protection, respectively. Broad absorption spectra in film(300-785 nm, 300-805 nm and 300-740 nm), low LUMO level(-3.92 e V,-3.67 e V,-3.66 e V) and a narrower energy gap(1.80 e V, 1.95 e V, 2.01 e V) were determined, nano-film surface roughness(RMS) values were 1.598 nm, 1.092 nm and 0.691 nm, respectively. Moreover, P(BDT-DTCDI) exhibited strong fluorescence properties(λmaxem=736 nm with excitation at 680 nm).In summary, it indicated that P(BDT-DTCDI) can be used in the fields of OTFTs and fluorescence material, P(BDT-PDI) and P(BDT-DTPDI) had an advantage for polymer solar cell applications as a stable n-type semiconductor.