Synthesis And Properties Of Dual-donor Imidazole-based Optoelectronic Materials

Organic light-emitting diodes（OLED）have unique structure and characteristics of ultra-thin,light weight,high brightness,low power consumption,it becomes an important part of display and lighting technology.Conjugated structures composed of donors and acceptors have attracted widespread attention as optoelectronic materials.Three series of donor-acceptor-donor（D-A-D’）type imidazole blue organic small molecule luminescent materials with indolocarbazole and triphenylamine as the dual donors and characterizes the structure were designed and synthesized in this paper.The main research contents are as follows:Firstly,five ethyl-substituted D-A-D’-type dual-donor imidazole derivatives were synthesized.The HOMO and LUMO of these compounds partially overlap and have a large energy level difference.They have blue emission peak in the region of 421-430nm.Solvent effect proved that these compounds have good characteristics of intramolecular charge transfer（ICT）.The typical aggregation induced emission（AIE）characteristics of these compounds can solve the fluorescence quenching of traditional luminescent materials.The non-doped devices were fabricated by using ethyl-substituted dual-donor imidazole derivatives as the light-emitting layer.The device II exhibited excellent EL performance,and the maximum brightness(L_max)was 5385 cd/m²,the maximum current efficiency was 2.68 cd/m²,and the maximum power efficiency was 1.53 lm/W.It showed the best performance because the electron withdrawing group（-F）was introduced in the compound;Next,five butyl-substituted D-A-D’-type dual-donor imidazole derivatives were synthesized.The extension of the alkyl chain increased the solubility of the compounds,which is beneficial to improve the processing performance of the device.The five molecules had good thermal properties that are beneficial to form a uniform amorphous film during evaporation,thereby improving the stability and life of the device.The introduction of different substituents can adjust the distribution of molecular orbitals,thereby balancing the charge transfer of molecules and regulating energy level matching with transporting in the manufacture of devices;Finally,five benzyl-substituted D-A-D’-type dual-donor imidazole derivatives were synthesized.The compounds all adopt non-coplanar conformations.The benzyl group and the indolocarbazole exhibited a nearly vertical twist.The introduction of the benzyl enhanced the rigidity of the molecule and improved the thermal stability of the compound,which is conducive to the construction of optoelectronic materials with excellent properties.And the introduction of the benzyl is benifited to used the vacuum evaporation method to manufacture the device that can maintain a stable shape during operation.The above results indicated that chemical modification can provide effective strategies to achieve high-efficiency OLEDs.