Solution processed single-emission layer white polymer light-emitting diodes with high color quality and high performance from a poly(N-vinyl)carbazole host.
Low cost and high performance white polymer light-emitting diodes (PLEDs) are very important as solid-state lighting sources. In this research three commercially available phosphors were carefully chosen, bis[2-(4,6-difluorophenyl)pyridinato-N,C(2)](picolinate)iridium(III) (FIrpic), bis[2-(2-pyridinyl-N)phenyl-C](2,4-pentanedionato-O(2),O(4))iridium(III) [Ir(ppy)2(acac)], and bis(2-phenyl-benzothiazole-C(2),N)(acetylacetonate)iridium(III) [Ir(bt)2(acac)], plus a home-made red phosphor of tris[1-(2,6-dimethylphenoxy)-4-(4-chlorophenyl)phthalazine]iridium(III) [Ir(MPCPPZ)3], and their photophysical and morphological properties were systematically studied as well as their applications in single-emission layer white PLEDs comprising poly(N-vinylcarbazole) as host. Additionally, the electrochemical properties and energy level alignment, possible energy transfer process, and thin-film morphology were also addressed. The binary blue/orange complementary white PLEDs exhibit stable electroluminescence spectra, wide spectrum-covering region range from 380-780 nm, and high color rendering index (CRI) over 70 with Commission Internationale de l'Eclairage coordinates x,y (CIEx,y) of (0.388, 0.440), correlated color temperature (CCT) of around 4400, plus high efficiency of 25.5 cd A(-1). The optimized red-green-blue white PLEDs showed a satisfactory CRI of around 82.4, maximum current efficiency of 20.0 cd A(-1) and external quantum efficiency (EQE) of 10.8%, corresponding to a CCT of 3700-2800, which is a warm-white hue. At last, stable and high color quality, red-green-orange-blue four component white PLEDs, with a CRI of over 82, a high efficiency of 24.0 cd A(-1), EQE of 11.5%, and high brightness of 43,569.9 cd m(-2) have been obtained.
Key Laboratory for Organic Electronics & Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, Nanjing 210023, China. iamshye@njupt.edu.cn iamwhuang@njupt.edu.cn.
Shang-Hui
SH
Ye
Tian-Qing
TQ
Hu
Zhou
Z
Zhou
Min
M
Yang
Mei-Han
MH
Quan
Qun-Bo
QB
Mei
Bang-Cheng
BC
Zhai
Zhen-Hong
ZH
Jia
Wen-Yong
WY
Lai
Wei
W
Huang