Alkyl group effect on small molecule emitter based on anthracene moiety in solution process

OLED device was fabricated by using 4,4'-bis[4-(di-p-tolylamino)styryl] biphenyl (DPAVBi) as dopant and 2-tert-butyl-9,10-di-naphthalen-2-yl-anthracene (TBADN), 2-Methyl-9,10-di-naphthalen-2-yl-anthracene (MADN) and 9,10-di-naphthalen-2-yl-anthracene (ADN), which are organic compounds and commercial blue materials, as hosts. The OLED device and the efficiency in OLED of which the emitting layers are prepared by deposition method and spin-coating method were compared. Deposited device showed high efficiency of 4.6-7.0cd/A in all the ADN derivatives. All ADN derivatives showed high efficiency of 4.6-7.0cd/A in the deposited device. In the case of device that was made through spin-coating, TBADN and MADN showed efficiency of 1.5-2.1cd/A, and in particular, no light was emitted for ADN. As a result of observing the film formed on PEDOT surface with spin-coating through SEM, TBADN and MADN exhibited an amorphous clear surface, but in case of ADN, crystalline domain had appeared. It was found that due to such crystallinity, light emission was prohibited as leakage current had increased due to increase of roughness on a surface. These results indicate that methyl and t-butyl groups at 2-position of anthracene prohibit crystallinity of molecule in spin-coating film.