FULL PAPER
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2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
1
wileyonlinelibrary.com
Dr. Z. Zhuang, Prof. B. Liu, Dr. Y. Li, Dr. T. Tao, Dr. J. Dai,
Dr. T. Zhi, Prof. Z. Xie, Prof. P. Chen, Prof. D. Chen,
Prof. Y. Shi, Prof. Y. Zheng, Prof. R. Zhang
Jiangsu Provincial Key Laboratory of Advanced Photonic
and Electronic Materials
School of Electronic Science and Engineering
Nanjing National Laboratory of Microstructures
Nanjing University
Nanjing 210093 , P. R. China
E-mail: bliu@nju.edu.cn ; rzhang@nju.edu.cn
Dr. X. Guo, Prof. H. Ge
College of Engineering and Applied Sciences
Nanjing National Laboratory of Microstructures
Nanjing University
Nanjing 210093 , P. R. China
Dr. F. Hu, Prof. X. Wang, Prof. M. Xiao
School of Physics
Nanjing National Laboratory of Microstructures
Nanjing University
Nanjing 210093 , P. R. China
light-emitting diodes (LEDs), the con-
ventional approach is to mainly use blue
emission from InGaN/GaN-based LEDs
radiatively pumping down-conversion
phosphor materials, such as Y
3
Al
5
O
12
:Ce
3+
(YAG), to provide longer wavelength emis-
sion components. However, these white
LEDs have a low color rendering index
(CRI) and high correlated color tem-
perature (CCT) owing to red emission
defi ciency in the visible spectrum.
[ 3 ]
In
addition, other issues still require consid-
eration such as the self-absorption of the
phosphor, the low effi ciency of the energy
transfer from the blue LED to the down-
conversion phosphor and the degradation
of phosphors.
[ 2,4,5 ]
To avoid these drawbacks by using
abovementioned phosphors, scientists
started to devote their efforts to devel-
oping phosphor-free white LEDs.
[ 4 ]
A
variety of approaches such as multichip
white LEDs, monolithic white LEDs,
and color-conversion white LEDs have
been extensively exploited.
[ 5–7 ]
Among them, color conversion
is regarded as the most popular method, and many different
materials have been used for color conversion in white light
generation instead of phosphors.
[ 2,8–15 ]
Very recently, a novel
organic energy down-converting material, [BODFluTh]
2
FB, has
been synthesized as an effective color converter for applica-
tion in hybrid inorganic/organic white LEDs, the chromaticity
coordinates of which are very close to the center of the chro-
maticity diagram where white light is located.
[ 16 ]
However, the
CCT of this hybrid inorganic/organic white LED is still that of
High Color Rendering Index Hybrid III-Nitride/
Nanocrystals White Light-Emitting Diodes
Zhe Zhuang , Xu Guo , Bin Liu , * Fengrui Hu , Yi Li , Tao Tao , Jiangping Dai , Ting Zhi ,
Zili Xie , Peng Chen , Dunjun Chen , Haixiong Ge , Xiaoyong Wang , Min Xiao , Yi Shi ,
Youdou Zheng , and Rong Zhang *
An excellent hybrid III-nitride/nanocrystal nanohole light-emitting diode
(h-LED) has been developed utilizing nonradiative resonant energy transfer
(NRET) between violet/blue emitting InGaN/GaN multiple quantum wells
(MQWs) and various wavelength emitting nanocrystals (NCs) as color-
conversion mediums. InGaN/GaN MQWs are fabricated into nanoholes by
soft nanoimprint lithography to minimize the separation between MQWs
and NCs. A signifi cant reduction in the decay lifetime of excitons in the
MQWs of the hybrid structure has been observed as a result of the NRET
from the nitride emitter to NCs. The NRET effi ciency of the hybrid structures
is obtained from the decay curves, as high as 80%. Moreover, a modifi ed
Förster formulation has exhibited that the exciton coupling distance in the
hybrid structures is less than the Förster’s radius, demonstrating a strong
coupling between MQWs and NCs. Finally, based on a systemic optimization
for white emission indexes, a series of hybrid ternary complementary color
h-LEDs have been demonstrated with a high color rendering index, up to 82,
covering the white light emission at different correlated color temperatures
ranging from 2629 to 6636 K, corresponding to warm white, natural white,
and cold white.
DOI: 10.1002/adfm.201502870
1. Introduction
The need has been emphasized for effi cient solid-state emit-
ters in applications ranging from displays to solid-state
lighting because they potentially provide substantial energy
savings to allow for effi cient energy utilization of limited
energy resources.
[ 1 ]
The last decades have seen unprecedented
achievements in the development of solid-state lighting
gradually and ultimately leading to lighting sources mainly
based on III-nitride semiconductors.
[ 2 ]
With regard to white
Adv. Funct. Mater. 2015,
DOI: 10.1002/adfm.201502870
www.afm-journal.de
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