황색 형광체가 분산된 백색 면광원 OLED소자의 연구

Abstract

Owing to various merits of OLED, it has been being actively studied as next generation flat panel display device at home and abroad. Especially, white organic light emitting device(WOLED) is possible to apply not only to display device but also to novel white solid state lighting In this paper we fabricated white organic light-emitting device through a mixture of yellow down-conversion phosphor and blue light-emitting polymer using spin-coating method. Poly[9,9-di-(2-ethylhexyl)-fluorenyl-2,7-diyl] end capped with N,N-Bis(4-methylphenyl)-4-aniline was used for blue emitting material and Ba₂Sio₄:Eu^(2+) was used as yellow down conversion phosphor. From pre-experiments, toluene was selected as solvent, and 2wt% polymer solution as base solution. due to emitting layer thickness by ellipsometry and FE-SEM. Finally WOLED was made using polymer-phosphor solution by spin coating methode and then Electro-luminescence property and CIE color coordinate were measured According to augmentation of yellow phosphor ratio, blue emission intensity was decreased and this decreasing was resulted by yellow emission intensity increasing. Also, CIE color coordinate was moved well from blue area to white area. However increment of x coordinate was more less than y coordinate increment. It was originated from weak Photo luminescence property of yellow phosphor in Orange and Red colours. Absorbtion and Excitation property was well distinguished near 500nm. and matched to PL, PLE spectra of Yellow Phosphor. The optimal result we achieved was CIE color coordinate of OLED x=0.266 y=0.33 with 30% yellow phosphor dispersion ratio and its driving voltage was 17V.