Superior white light emission and color tunability of
tri-doped YBO
3
:Tb
3+
, Eu
3+
and Dy
3+
for white light
emitting diodes†
Kaushik Das,
a
Archis Marathe,
a
Xianwen Zhang,
b
Zhi Zhao
*
c
and Jharna Chaudhuri
*
a
A tri-doped YBO
3
:Tb
3+
, Eu
3+
and Dy
3+
phosphor, which is capable of producing white light by combining
blue, green, yellow, orange and red emissions when excited at 365 nm ultraviolet (UV) light, was developed
using a general hydrothermal method. The samples showed strong photoluminescence spectra at 485, 541,
578, 591, 611, and 627 nm under the excitation wavelength of 365 nm (ultraviolet light) indicating the
presence of blue, green, yellow, orange and red light due to the transitions
4
F
9/2
/
6
H
15/2
(Dy
3+
),
5
D
4
/
7
F
5
(Tb
3+
),
4
F
9/2
/
6
H
13/2
(Dy
3+
),
5
D
0
/
7
F
1
(Eu
3+
) and
5
D
0
/
7
F
2
(Eu
3+
), respectively. Tri-doping is
seemed to be more successful in the creation of white light. The effect of the variations in doping
percentages on color tunability was also evident. Evidence of efficient energy transfers from the host
excitations to activators Tb
3+
and Eu
3+
, and from Dy
3+
to Tb
3+
to Eu
3+
existed. Although there is a weak
energy transfer from host to Dy
3+
occurred, strong photoluminescence excitation bands existed in Dy
3+
.
1. Introduction
Orthoborates (commonly denoted as REBO
3
, where RE ¼ Rare
Earths ¼ Y, La, Gd, and Lu), doped with lanthanide ions (Eu
3+
,
Ce
3+
, Dy
3+
, or Tb
3+
), have taken a prominent position among the
phosphors and have a wide range of applications. These phos-
phors have strong photoluminescence (PL) intensity and
exceptional optical damage threshold, and are very stable.
1–7
One of the important applications of these phosphors are the
(LEDs). YBO
3
is seemingly more popular among the REBO
3
s due
to its excellent ultraviolet absorption and high chemical
stability.
7–13
The development of solid-state lighting has shied the focus
to create high-efficiency and high-quality white light using light-
emitting diodes (WLEDs). Solid-state LEDs have always been in
the limelight due to emission efficiencies as high as 95% which
are much higher than incandescent and uorescent lights.
14,15
The greatest disadvantage of these LEDs is that the light emis-
sion ranges within a few nanometers. So additional materials,
in most cases the inorganic phosphors are used to expand the
emission spectrum. The phosphors are mostly doped with rare
earth (RE) ions as this process causes highly stable f–f energy
level transitions and a broad range of emission wavelengths.
High quality and efficient white light are produced by, doping
complex inorganic hosts with dopants. The methods to
synthesize these inorganic hosts are complicated and or
expensive. First commercially available WLED was prepared by
combining Gallium Nitride (GaN) chip with yttrium aluminum
garnet (YAG) doped with cerium which is the prominent prac-
tice still today.
16
White color produced from this method suffers
from poor color rendering index as the YAG doped cerium
doesn't have sufficient red light emission. The condition is
improved by adding red phosphor. Another method is
combining UV LED chip with a white light-emitting single-
phosphor. Again this method also suffers the same problem
as described in the previous method. Some dopants like Tb
3+
,
Eu
3+
, Dy
3+
or Ce
3+
can absorb UV radiation and their emissions
are between green to red band.
In our recent works, we have reported a general hydro-
thermal method successfully used without any additional
organic solvent or surfactant for the synthesis of YBO
3
:Eu
3+
with
the highest chromaticity (red/orange photoluminescence
emission) value.
7
For the rst time, synthesis of YBO
3
:Tb
3+
, Eu
3+
phosphors with white and tunable luminescence under UV
excitation and by varying the relative ratio of Tb
3+
and Eu
3+
doping was also reported by our group.
9
Due to incorporation of
Tb
3+
and Eu
3+
ions into YBO
3
,efficient energy transfers from the
host excitations to activators, as well as from Tb
3+
to Eu
3+
,
occurred. In addition, our group has reported structural and
optical studies of YBO
3
when tri-doped with Eu
3+
, Ce
3+
, and
Tb
3+
, focusing on the role of terbium concentration. It has been
shown that the PL excitation bands related to both Ce
3+
and
Tb
3+
increase in intensity for red emission from the Eu
3+
with
a
Department of Mechanical Engineering, Texas Tech University, Lubbock, Texas, USA.
E-mail: jharna.chaudhuri@ttu.edu; Fax: +1-806-742-3540; Tel: +1-503-509-8421
b
School of Automobile and Transportation Engineering, Hefei University of Technology,
Hefei, Anhui 230009, China
c
Hefei National Laboratory for Physical Sciences at the Microscale, University of
Science & Technology of China, Hefei, Anhui 230026, China. E-mail: zhizhao@ustc.
edu.cn
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c6ra18217h
Cite this: RSC Adv. , 2016, 6, 95055
Received 18th July 2016
Accepted 22nd September 2016
DOI: 10.1039/c6ra18217h
www.rsc.org/advances
This journal is © The Royal Society of Chemistry 2016 RSC Adv. , 2016, 6, 95055–95061 | 95055
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