A simple unilateral homogenous PhOLEDs with enhanced efficiency and reduced efficiency roll-off

doi:10.1007/s12200-013-0349-3

Front Optoelec

2013, Vol. 6

Issue (4) : 435-439 https://doi.org/10.1007/s12200-013-0349-3

RESEARCH ARTICLE

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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Abstract

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,Email:wanglei@mail.hust.edu.cn

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.

URL:

https://academic.hep.com.cn/foe/EN/10.1007/s12200-013-0349-3
https://academic.hep.com.cn/foe/EN/Y2013/V6/I4/435

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)

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

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