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Frontiers of Optoelectronics

Front Optoelec    2013, Vol. 6 Issue (4) : 435-439
A simple unilateral homogenous PhOLEDs with enhanced efficiency and reduced efficiency roll-off
Shaoqing ZHUANG, Wenzhi ZHANG, Xiao YANG, Lei WANG()
Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
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In this paper, highly efficient phosphorescent organic lighting emitting diodes (PhOELDs) with low efficiency roll-off are demonstrated by using a unilateral homogenous device structure with wide band-gap material 4, 4', 4″-tri(N-carbazolyl)-triphenylamine (TCTA) as hole transporting layer and emitting layer (EML). The optimized blue device exhibits a high power efficiency of 40 lm/W, external quantum efficiency of 19.2% and current efficiency of 37.7 cd/A. More importantly, the device exhibits a low efficiency roll-off at 1000 cd/m2. In addition, the white homogenous PhOLEDs only exhibits the efficiency roll-off 5.6% and 17.5%, corresponding to the brightness of 1000 and 5000 cd/m2 respectively. These interesting results demonstrate that the simple unilateral homogenous device structure is a promising way to enhance the device efficiency and reduce the efficiency roll-off.

Keywords enhance efficiency      efficiency roll-off      unilateral homogenous structures     
Corresponding Author(s): WANG Lei,   
Issue Date: 05 December 2013
 Cite this article:   
Shaoqing ZHUANG,Wenzhi ZHANG,Xiao YANG, et al. A simple unilateral homogenous PhOLEDs with enhanced efficiency and reduced efficiency roll-off[J]. Front Optoelec, 2013, 6(4): 435-439.
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Fig.1  Absorption (Abs) spectra of FIrpic and orange ((fbi)Ir(acac)); photoluminescence (PL) spectra of pure TCTA, FIrpic and orange doped TCTA and FIrpic
Fig.2  Structure and energy levels of unilateral homogenous device (device 1) and control device (device 2). ITO: indium tin oxide; HOMO: highest occupied molecular orbital; LUMO: lowest unoccupied molecular orbital
Fig.3  (a) curves of the devices 1 and 2; (b) current efficiency of unilateral homogenous device (device 1) and control device (device 2) at different brightness. Inset: EL spectrum of unilateral homogenous device (device 1) and control device (device 2)
Va)EQEmaxLEmaxLE1000 cd/m2LE 5000 cd/m2LE 10000 cd/m2
Tab.1  EL performance of blue and white PhOLEDs at different conditions
Fig.4  Thickness of excition recombination zone in homogenous device
Fig.5  Current efficiency of white PhOLED with homogenous structure and control structure. Inset: EL spectrum of different device structures
1 Tang C W, VanSlyke S A. Organic electroluminescent diodes. Applied Physics Letters , 1987, 51(12): 913-915
doi: 10.1063/1.98799
2 Fukase A, Dao K L T, Kido J. High-efficiency organic electroluminescent devices using iridium complex emitter and arylamine-containing polymer buffer layer. Ploymers for Advanced Technologies , 2002, 13(8): 601-604
doi: 10.1002/pat.229
3 Tanaka D, Sasabe H, Li Y J, Su S J, Takeda T, Kido J. Ultra high efficiency green organic light-emitting devices. Japanese Journal of Applied Physics , 2007, 46(1): L10-L12
doi: 10.1143/JJAP.46.L10
4 Su S J, Tanaka D, Li Y J, Sasabe H, Takeda T, Kido J. Novel four-pyridylbenzene-armed biphenyls as electron-transport materials for phosphorescent OLEDs. Organic Letters , 2008, 10(5): 941-944
doi: 10.1021/ol7030872 pmid:18237184
5 Kim H, Cho N S, Oh H Y, Yang J H, Jeon W S, Park J S, Suh M C, Kwon J H. Highly efficient red phosphorescent dopants in organic light-emitting devices. Advanced Materials , 2011, 23(24): 2721-2726
doi: 10.1002/adma.201100405 pmid:21495090
6 Fan C H, Sun P, Su T H, Cheng C H. Host and dopant materials for idealized deep-red organic electrophosphorescence devices. Advanced Materials , 2011, 23(26): 2981-2985
doi: 10.1002/adma.201100610 pmid:21567483
7 Malliaras G G, Scott J C. The roles of injection and mobility in organic light emitting diodes. Journal of Applied Physics , 1998, 83(10): 5399-5403
doi: 10.1063/1.367369
8 Polikarpov E, Swensen J S, Chopra N, So F, Padmaperuma A B. An ambipolar phosphine oxide-based host for high power efficiency blue phosphorescent organic light emitting devices. Applied Physics Letters , 2009, 94(22): 223304
doi: 10.1063/1.3148642
9 Gong S, Chen Y, Luo J, Yang C, Zhong C, Qin J, Ma D. Bipolar tetraarylsilanes as universal hosts for blue, green, orange, and white electrophosphorescence with high efficiency and low efficiency roll-off. Advanced Functional Materials , 2011, 21(6): 1168-1178
doi: 10.1002/adfm.201002066
10 Chou H H, Cheng C H. A highly efficient universal bipolar host for blue, green, and red phosphorescent OLEDs. Advanced Materials , 2010, 22(22): 2468-2471
doi: 10.1002/adma.201000061 pmid:20446307
11 Xiao L, Su S J, Agata Y, Lan H, Kido J. Nearly 100% internal quantum efficiency in an organic blue-light electrophosphorescent device using a weak electron transporting material with a wide energy gap. Advanced Materials , 2009, 21(12): 1271-1274
doi: 10.1002/adma.200802034
12 Lee J H, Huang C L, Hsiao C H, Leung M K, Yang C C, Chao C C. Blue phosphorescent organic light-emitting device with double emitting layer. Applied Physics Letters , 2009, 94(22): 223301
doi: 10.1063/1.3147866
13 Zhang X W, Li J, Khan M, Zhang L, Jiang X Y, Haq K, Zhu W Q, Zhang Z L. Improved chromaticity and electron injection in a blue organic light-emitting device by using a dual electron-transport layer with hole-blocking function. Semiconductor Science and Technology , 2009, 24(7): 075021
doi: 10.1088/0268-1242/24/7/075021
14 Cai C, Su S J, Chiba T, Sasabe H, Pu Y J, Nakayama K, Kido J. Efficient low-driving-voltage blue phosphorescent homojunction organic light-emitting devices. Japanese Journal of Applied Physics , 2011, 50(4): 040204
doi: 10.1143/JJAP.50.040204
15 Tsuji H, Mitsui C, Sato Y, Nakamura E. Bis(carbazolyl)benzodifuran: a high-mobility ambipolar material for homojunction organic light-emitting diode devices. Advanced Materials , 2009, 21(37): 3776-3779
doi: 10.1002/adma.200900634
16 Wang Q, Tao Y, Qiao X, Chen J, Ma D, Yang C, Qin J. High-performance, phosphorescent, top-emitting organic light-emitting diodes with p-i-n homojunctions. Advanced Functional Materials , 2011, 21(9): 1681-1686
doi: 10.1002/adfm.201002229
17 Jang S E, Yook K S, Lee J Y. High power efficiency in simplified two layer blue phosphorescent organic light-emitting diodes. Organic Electronics , 2010, 11(6): 1154-1157
doi: 10.1016/j.orgel.2010.04.004
18 Qiao X, Tao Y, Wang Q, Ma D, Yang C, Wang L, Qin J, Wang F. Controlling charge balance and exciton recombination by bipolar host in single-layer organic light-emitting diodes. Journal of Applied Physics , 2010, 108(3): 034508
doi: 10.1063/1.3457672
19 Zhang H, Huo C, Zhang J, Zhang P, Tian W, Wang Y. Efficient single-layer electroluminescent device based on a bipolar emitting boron-containing material. Chemical Communications (Cambridge) , 2006, (3): 281-283
doi: 10.1039/b513918j
20 Seo J H, Lee S J, Seo B M, Moon S J, Lee K H, Park J K, Yoon S S, Kim Y K. White organic light-emitting diodes showing nearly 100% internal quantum efficiency. Organic Electronics , 2010, 11(11): 1759-1766
doi: 10.1016/j.orgel.2010.07.015
21 Chen H, Lee J, Shiau C. Electromagnetic modeling of organic light-emitting devices. Journal of Lightwave Technology , 2006, 24(6): 2450-2457
doi: 10.1109/JLT.2006.874591
22 Su S J, Chiba T, Takeda T, Kido J. Pyridine-containing triphenylbenzene derivatives with high electron mobility for highly efficient phosphorescent OLEDs. Advanced Materials , 2008, 20(11): 2125-2130
doi: 10.1002/adma.200701730
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