Nitrogenous Heterocyclic Base Perylene Electronic Transmission Of Materials Research

With the rapid developments of organic optoelectronic devices, such as light-emitting diodes (OLEDs), field-effect transistors, and solar cells, it becomes an impending need to develop organic electron-transport (n-type) materials with high mobility, good stability in air and solution processing. In this dissertation, based on molecular and material designs, electron-deficient nitrogen heterocycles were introduced to the traditional organic n-type materials of perylene diimides. The effects of nitrogen heterocycle groups on energy levels, electron-accepting ability and stability were investigated in details. The unsymmetrical perylene diimides were also prepared by chemical modification, in order to obtain the organic semiconductor materials possessing high performance and solution processing.First of all, a series of nitrogen heterocycle substituted perylene diimides were synthesized through the nucleophilic reactions between 3,4,9,10-perylene tetracaboxylic dianhydride (PTCDA) and heterocyclic amines: N,N'-dipyrimidinyl-3,4,9,10-perylenetetracarboxylic diimide (DMP), N,N'-dipyrazinyl-3,4,9,10-perylene tetracarboxylic diimide (DZP), and N,N'-dichloropyridazinyl-3,4,9,10-perylene tetracarboxylic diimide (DDP). Their molecular structures were characterized by FTIR spectra and elemental analysis.The influence of pyrimidinyl group on the energy levels of perylene diimides was investigated though UV-Vis absorption and cyclic voltammetry (CV). The results indicated that the introduction of pyrimidinyl to perylene diimides lowered the LUMO energy level and resulted in a little red shift of its absorption in solution. The air stability of DMP and DPP were investigated, and it was found that the existence of pyrimidinyl elevated the thermal decomposition temperature in air, and thus enhanced the ability of oxidation resistance. Fluorescence quenching observed in a dual-layer film consisting of a DMP layer and a C₆₀ layer was attributed to the charge transfer at the interface due to the energy level offset between DMP and C₆₀.Two unsymmetrical perylene diimides were designed and synthesized:N-dodecyl-N'-pyrimidinyl-3,4,9,10-perylenetetracarboxylic diimide (DoMP), N-dodecyl-N'-phenyl-3,4,9,10-perylenetetracarboxylic diimide (DoPP). Their molecular structures were characterized by FTIR spectra and elemental analysis.The long chain of alkyl increased the solubility of perylene diimides. It was found that the influence of pyrimidinyl on band gap disappeared after introduction of alkyl, but the pyrimidinyl still lowered the LUMO energy level. The air stability of DoMP and DoPP was also studied, which indicated that the thermal stability and the ability of oxidation resistance degenerated greatly after the introduction of alkyl.The influence of solvent and temperature on the aggregation of DoMP solution-cast film was simply investigated though UV-Vis absorption and Microscope. It was found that chloroform solution-cast film of DoMP possessed amorphousstructure. But after adding DMF into the solution, the order degree of the solution-cast film increased. When temperature elevated (not beyond 150℃), no changes happened in the UV-Vis absorption of solution-cast film of DoMP, indicating almost no change in aggregation. However, the optical topographic images indicated that the grain size increased with increasing the temperature.