APPLIED PHYSICS VOLUME: 15 |NUMBER: 5 |2017 |DECEMBER
E ec s o G een - Emi ing Phospho
(La,Ce,Tb)PO4:Ce:Tb on Luminous Flux and Colo
Quali y o Whi e LED Lamps
Nguyen Thi Phuong THAO1,4, Phan Xuan LE2, Le Van THO3,
Mi osla VOZNAK4, Nguyen Doan Quoc ANH5
1Facul y o Elec ical and Elec onics Enginee ing, Ton Duc Thang Uni e si y,
19 Nguyen Huu Tho S ee , 7 h Dis ic , Ho Chi Minh Ci y, Vie nam
2Facul y o Elec ical and Elec onics Enginee ing, HCMC Uni e si y o Food Indus y,
140 Le T ong Tan s ee , Tay Thanh Wa d, Tan Phu Dis ic , Ho Chi Minh ci y, Vie nam
3Ins i u e o T opical Biology, Vie nam Academy o Science and Technology,
85 T an Quoc Toan s ee , 3 h Dis ic , Ho Chi Minh Ci y, Vie nam
4Depa men o Telecommunica ions, Facul y o Elec ical Enginee ing and Compu e Science,
VSB–Technical Uni e si y o Os a a, 17. lis opadu 15/2172, 708 33 Os a a, Czech Republic
5Powe Sys em Op imiza ion Resea ch G oup, Facul y o Elec ical and Elec onics Enginee ing,
Ton Duc Thang Uni e si y, 19 Nguyen Huu Tho S ee , 7 h Dis ic , Ho Chi Minh Ci y, Vie nam
nguyen hiph[email p o ec ed], [email p o ec ed], [email p o ec ed],
mi osla . [email p o ec ed], nguyendoanquo[email p o ec ed]
DOI: 10.15598/aeee. 15i5.2111
Abs ac . In his pape , we p esen and analyze
he in luence o (La,Ce,Tb)PO4:Ce:Tb g een phospho
(LaTb) owa d he pe o mance o he mul i-chip whi e
LED (MCW-LEDs) lamps including colo uni o mi y,
lumen ou pu , Colo Rende ing Index (CRI), and Colo
Quali y Scale (CQS). By mixing he LaTb g een phos-
pho and he YAG:Ce yellow phospho compounding
unde condi ion o 7000 K MCW-LEDs, his new ap-
p oach can p oduce a huge meaning ul change in lu-
men ou pu and he angula colo dis ibu ion o MCW-
LEDs. We also s udy he in e ac ion be ween he con-
cen a ion and size o he LaTb pa icles wi h ou pu
lux, colo uni o mi y, CRI, and CQS. The ob ained
esul s demons a e ha he highe lumen ou pu , he
highe colo uni o mi y enhancemen could be a ained
by adding he LaTb pa icles wi h a size ange a ound
6-8 µm and he concen a ion a ound 1.5 % in phos-
pho laye . Meanwhile, he dec ease o he colo en-
de ing alue (CRI) and he Colo Quali y Scale (CQS)
end o be s able and insigni ican . In o he wo ds,
he ob ained esul s p o ide a p ospec i e me hod which
plays an impo an ole in he de elopmen o MCW-
LED manu ac u ing echnology.
Keywo ds
(La,Ce,Tb)PO4:Ce:Tb phospho , Colo Qual-
i y Scale, Colo Rende ing Index, colo uni-
o mi y, luminous lux, mul i-chip whi e LED
lamp.
1. In oduc ion
Recen ly, MCW-LED is becoming one o he mos
widely used ligh ing sou ces in illumina ion ap-
plica ions since i s cha ac e is ics such as high ligh
in ensi y, ene gy-e icien , low powe consump ion, as
esponse, and expended du abili y ou pe o m con en-
ional ligh ing sou ces (Michael Can o e e al. 2015
and Yu e al. 2016). Ne e heless, he e a e challenges
in imp o ing hose pe o mance indica o s. Tha leads
o u he esea ch and de elopmen . Two impo an
p ope ies o whi e LEDs ha a ac g ea a en ion
o esea che s a e lumen ou pu and colo uni o mi y
which ha e been s udied and published in p e ious
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pape s o Ying e al. (2016) and Chiang e al (2015).
To imp o e hese wo ea u es, hese pape s we e
mainly ocused on sca e ing enhancemen o he in-
ciden and he con e ed ligh o phospho pa icles in
MCW LED.
Whi e ligh , which is p oduced by whi e LED, is he
esul o mixing in he inciden blue ligh om he chips
and con e ed yellow ligh . YAG:Ce yellow phospho
pa icles a e he p e e ed ma e ial o whi e LEDs.
This phospho is used o abso b exci ing blue ligh om
he chips and o emi he yellow ligh (Liu e al. 2008,
Liu e al. 2011). Howe e , i is pe cei ed ha he blue
ligh in ensi y is no in balance wi h he yellow ligh
in ensi y due o he backsca e ing p oblems. Conse-
quen ly, he MCW-LEDs do no o e uni o m colo
dis ibu ion and hus a e no sui able o some appli-
ca ions (H-C Chen e al. 2013 and K-J Chen e al.
2012).
One o he al e na i e me hods o enhance he
colo uni o mi y and luminous lux o whi e LEDs is
o add g een Ce0.67Tb0.33 MgAl11 O19:Ce,Tb phos-
pho in o phospho compounding wi h he sui able
phospho concen a ion as p oposed by Anh e al.
(2016). In addi ion, Hakeem and Pa k (2015) in-
oduced Na(S 072Ca0.25)PO4:0.03Eu2+ phospho ha
showed s onge emission spec a in ensi y in whi e
LEDs and could be employed as a blue emi ing phos-
pho o LEDs. O he s udies ound ha he use
o app op ia e concen a ion and hickness as well as
sui able loca ion o phospho laye can help achie e
be e LED pe o mance (Shuai e al. 2011). Mo e-
o e , he e ec o LED lens on op ical quali ies ha e
also been s udied ecen ly. Fo example, Enguo Chen
(2014) demons a ed ha a s uc u e wi h a ee o m
mic olens a ay could imp o e he luminous lux o
whi e LEDs. The lens wi h he d ople e apo a ion
exhibi s a s onge ligh in ensi y (Xing Guo e al.
2016). Al hough he e we e di e en app oaches o in-
ensi y he e iciency o whi e LEDs, he angula colo
uni o mi y and he lumen ou pu o whi e LEDs a e
s ill no high enough and insu icien o sa is y equi e-
men s and inc easing demand o applica ions in he
comme cial LED ligh ing ma ke . The e o e, ad anced
esea ch should be conduc ed o achie e he desi ed
colo uni o mi y and highe lumen ou pu .
In his s udy, we p opose he inco po a ion o he
new g een LaTb pa icles in he phospho laye o he
MCW-LEDs o enhance he lumen ou pu and he co -
ela ed colo empe a u e uni o mi y. Th ough he ex-
amina ion o he e ec o g een (La,Ce,Tb)PO4:Ce:Tb
phospho on he whi e LED illumina ion in In-cup
Phospho Packages (IPP), we ound ha LaTb pa i-
cles can p o ide be e ligh dis ibu ion in he MCW-
LED package. The simula ion o his package is ca ied
ou on a ious weigh pe cen ages and di e en sizes
o LaTb phospho pa icles. The sca e ing p ope ies
o phospho laye a e in es iga ed by conside ing bo h
ligh abso p ion and ligh con e sion in LEDs when
LaTb pa icles a e injec ed in o phospho laye . In
o he wo ds, his wo k in es iga es how bo h concen-
a ion and size o LaTb g een phospho pa icles will
impac on luminous lux, angula colo dis ibu ion,
CRI, and CQS.
2. Simula ion and
Compu a ion
The main pu pose o his esea ch is o e eal he e ec
o g een LaTb phospho on he angula CCT uni o -
mi y and he lumen ou pu e iciency o he MCW-
LEDs, so we used a 7000 K MCW-LED wi h in-cup
phospho s uc u e o simula e. The MCW-LED mod-
els used in he simula ion p ocesses we e he comme -
cial MPBGA (Mul i-Package Ball G id A ay) p o-
ided by he Siliconwa e P ecision Indus ies Co. L d.,
Taiwan.
The model s uc u e, as shown in Fig. 1, was buil up
acco ding o he MCW-LED samples which consis s o
a blue chip, a e lec o cup, a phospho laye , and a sil-
icone laye . Each blue chip was designed wi h 1.16 W
adian powe , a peak wa eleng h o 453 nm, and a di-
mension o 1.14 mm ×0.15 mm. These chips we e
secu ely a ached o he e lec o which has a 2.07 mm
PHYSICS AND OPTICS VOLUME: XX | NUMBER: X | 2015 | MONTH
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op ical quali ies ha e also been s udied ecen ly. Fo
example, Enguo Chen (2014) demons a ed ha a
s uc u e wi h a ee o m mic olens a ay could imp o e
he luminous lux o whi e LEDs. The lens wi h he
d ople e apo a ion exhibi s a s onge ligh in ensi y
(Xing Guo e al. 2016). Al hough he e we e di e en
app oaches o in ensi y he e iciency o whi e LEDs, he
angula colo uni o mi y and he lumen ou pu o whi e
LEDs a e s ill no high enough and insu icien o sa is y
equi emen s and inc easing demand o applica ions in
he comme cial LED ligh ing ma ke . The e o e,
ad anced esea ch should be conduc ed o achie e he
desi ed colo uni o mi y and highe lumen ou pu .
In his s udy, we p opose he inco po a ion o he new
g een LaTb pa icles in he phospho laye o he MCW-
LEDs o enhance he lumen ou pu and he co ela ed
colo empe a u e uni o mi y. Th ough he examina ion o
he e ec o g een (La,Ce,Tb)PO4:Ce:Tb phospho on he
whi e LED illumina ion in in-cup phospho packages
(IPP), we ound ha LaTb pa icles can p o ide be e
ligh dis ibu ion in he MCW-LED package. The
simula ion o his package is ca ied ou on a ious
weigh pe cen ages and di e en sizes o LaTb phospho
pa icles. The sca e ing p ope ies o phospho laye a e
in es iga ed by conside ing bo h ligh abso p ion and
ligh con e sion in LEDs when LaTb pa icles a e
injec ed in o phospho laye . In o he wo ds, his wo k
in es iga es how bo h concen a ion and size o LaTb
g een phospho pa icles will impac on luminous lux,
angula colo dis ibu ion, CRI, and CQS.
2. Simula ion and Compu a ion
The main pu pose o his esea ch is o e eal he
e ec o g een LaTb phospho on he angula CCT
uni o mi y and he lumen ou pu e iciency o he MCW-
LEDs, so we used a 7000K MCW-LED wi h in-cup
phospho s uc u e o simula e. The MCW-LED models
used in he simula ion p ocesses we e he comme cial
MPBGA (Mul i-Package Ball G id A ay) p o ided by
he Siliconwa e P ecision Indus ies Co. L d., Taiwan.
The model s uc u e, as shown in Fig.1, was buil up
acco ding o he MCW-LED samples which consis s o a
blue chip, a e lec o cup, a phospho laye , and a silicone
laye . Each blue chip was designed wi h 1.16W adian
powe , a peak wa eleng h o 453nm, and a dimension o
1.14mm x 0.15mm. These chips we e secu ely a ached o
he e lec o which has a 2.07 mm dep h, 8 mm bo om
leng h, and 9.85mm su ace leng h. The chips we e
co e ed by a 0.08 mm hick phospho laye , as shown in
Fig. 1. In o de o be e unde s and he e ec o using
his g een phospho , he op ical simula ion p ocess is
conduc ed wi h a ia ion o LaTb pa icle concen a ion
and size. I is wo h no ing ha i he concen a ion o
g een LaTb phospho a ies, he YAG: Ce phospho
concen a ion needs o be sui ably adjus ed o main ain
he colo empe a u e o whi e LEDs a 7000K.
Fig. 1: Illus a ion o MCW-LEDs s uc u e: (a) he sample LED used
in his s udy (b) wi h in-cup phospho con igu a ion
Ligh Tools 8.1.0 op ical so wa e was used in his
simula ion p ocess o model he LED s uc u e and
analyze i s op ical pe o mance. The LaTb phospho
wi h he wa eleng h a 546 nm was added o he MCW-
LED wi h he se e al al e a ions in concen a ion and size
o op imize he op ical p ope ies o LEDs. The e o e,
hese MCW-LEDs con ain he g een phospho LaTb, he
yellow phospho YAG:Ce, and he silicone glues in hei
phospho laye . In his s uc u e, g een LaTb phospho
pa icle sizes we e anging om 1 µm o 10 µm, while
he adius o he YAG: Ce yellow phospho pa icle is se
o 7.25 µm.
The sca e ing o he LaTb phospho pa icles is
calcula ed and e i ied by ollowing he Mie- heo y (Lai
e al. 2016). The ela ionship among he angula
sca e ing ampli udes and he weigh as well as he size o
he LaTb pa icles is desc ibed by he ollowing
equa ions:
 
1
1
2 1
( , ) (cos ) ( , ) (cos )
( 1) n n n n
n
n
S a x m b x m
n n
   



 


 
2
1
2 1
( , ) (cos ) ( , ) (cos )
( 1) n n n n
n
n
S a x m b x m
n n
   



 


whe e S1, S2 a e he sca e ing in ensi y unc ions, x is he
pa icle size pa ame e , m is he phospho pa icle
e ac i e index. Thei alues a e de e mined by he
angula unc ions
(cos )
n
 
and
(cos )
n
 
, he pa ame e s
m, x, and he expansion coe icien s an, bn. The e ac i e
index o phospho pa icle is se o be 1.85 and 1.83 o
LaTb and YAG: Ce. The sca e ing in ensi y S1, S2 o
MCW-LEDs a e simula ed and compu ed a he peak o
555 nm o yellow YAG: Ce phospho and he wa eleng h
o 453nm o blue chips. Figu e 2 depic s he angula
sca e ing in ensi y o LaTb and YAG: Ce pa icles on he
Ca esian coo dina e sys em. The Ma lab simula ion
esul s in Fig. 2 exp ess ha he angula sca e ing
in ensi y o LaTb di use pa icle is simila o he yellow
(1)
(2)
(a) (b)
(a) he sample LED used in his
s udy
YAG:Ce LaTb
Silicone lens
(b) wi h in-cup phospho con igu a ion
Fig. 1: Illus a ion o MCW-LEDs s uc u e.
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dep h, 8 mm bo om leng h, and 9.85 mm su ace
leng h. The chips we e co e ed by a 0.08 mm hick
phospho laye , as shown in Fig. 1. In o de o be e
unde s and he e ec o using his g een phospho , he
op ical simula ion p ocess is conduc ed wi h a ia ion
o LaTb pa icle concen a ion and size. I is wo h
no ing ha i he concen a ion o g een LaTb phos-
pho a ies, he YAG:Ce phospho concen a ion needs
o be sui ably adjus ed o main ain he colo empe -
a u e o whi e LEDs a 7000 K.
Ligh Tools 8.1.0 op ical so wa e was used in his
simula ion p ocess o model he LED s uc u e and
analyze i s op ical pe o mance. The LaTb phospho
wi h he wa eleng h a 546 nm was added o he MCW-
LED wi h he se e al al e a ions in concen a ion and
size o op imize he op ical p ope ies o LEDs. The e-
o e, hese MCW-LEDs con ain he g een phospho
LaTb, he yellow phospho YAG:Ce, and he silicone
glues in hei phospho laye . In his s uc u e, g een
LaTb phospho pa icle sizes we e anging om 1 µm
o 10 µm, while he adius o he YAG:Ce yellow phos-
pho pa icle is se o 7.25 µm.
The sca e ing o he LaTb phospho pa icles is cal-
cula ed and e i ied by ollowing he Mie- heo y (Lai e
al. 2016). The ela ionship among he angula sca e -
ing ampli udes and he weigh as well as he size o he
LaTb pa icles is desc ibed by he ollowing equa ions:
S1=
∞
X
n=1
2n+ 1
n(n+ 1) [an(x, m)πn(cos θ)
+bn(x, m)τn(cos θ)] ,
(1)
S2=
∞
X
n=1
2n+ 1
n(n+ 1) [an(x, m)τn(cos θ)
+bn(x, m)πn(cos θ)] ,
(2)
Angle (deg ee)
0 50 100 150
Rela i e In ensi y (a.u.)
#10-3
0
1
2
3
4
5
6
7LaTb
YAG:Ce
Fig. 2: The angula sca e ing diag am o LaTb and YAG:Ce
pa icles in he phospho laye o MCW-LEDs o
546 nm and 555 nm.
whe e S1,S2a e he sca e ing in ensi y unc ions, xis
he pa icle size pa ame e , mis he phospho pa icle
e ac i e index. Thei alues a e de e mined by he
angula unc ions πn(cos θ)and τn(cos θ), he pa ame-
e s m,x, and he expansion coe icien s an,bn. The
e ac i e index o phospho pa icle is se o be 1.85
and 1.83 o LaTb and YAG:Ce. The sca e ing in en-
si y S1,S2o MCW-LEDs a e simula ed and compu ed
a he peak o 555 nm o yellow YAG:Ce phospho and
he wa eleng h o 453 nm o blue chips.
Figu e 2 depic s he angula sca e ing in ensi y o
LaTb and YAG:Ce pa icles on he Ca esian coo di-
na e sys em. The Ma lab simula ion esul s in Fig. 2
exp ess ha he angula sca e ing in ensi y o LaTb
di use pa icle is simila o he yellow YAG:Ce phos-
pho pa icle. Hence, he combina ion o he LaTb
pa icles and he YAG:Ce phospho laye will p o-
duce a sca e ing enhancemen o he inciden ligh in
MCW-LED.
3. Resul s and Discussion
To de e mine he colo uni o mi y quali y o LEDs,
we use he Co ela ed Colo Tempe a u e de ia ion
(4CCT) which is he di e ence be ween he maximum
CCT alue and he minimum CCT alue. This pa am-
e e was also cha ac e izes he angula CCT uni o mi y
o LEDs. Thus, lowe 4CCT alue co esponds o he
be e ligh quali y o LEDs (K-C Huang e al. 2013).
Figu e 3 shows he ela ionship among 4CCT, he
concen a ion, and size o LaTb pa icles. When he
LaTb pa icle concen a ion inc eases, he CCT de ia-
ion ema kably dec eases all LaTb pa icles wi h di -
e en sizes. I he concen a ion o LaTb phospho
inc eases om 0 o 1.4 % o small LaTb pa icles and
om 0 up o 1.8 % o bigge sizes, LED shows an ex-
Concen a ion (%)
0 0.5 1 1.5
"CCT (K)
0
1000
2000
3000
4000
5000
1 2 3 4 5 6 7 8 9 10
Fig. 3: The CCT de ia ion (4CCT) o MCW-LEDs is a a e -
age CCT 7000 K wi h di e en LaTb pa icle sizes and
concen a ions.
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cellen colo uni o mi y in i s op ical p ope y. In some
cases, 4CCT signi ican ly educes om 4000 K o less
han 500 K. The lowes CCT de ia ion alue can be
achie ed o less han 450 K a he LaTb pa icle con-
cen a ion o 0.4 % and pa icle size o 1 µm. Hence,
LaTb phospho could p o ide g ea sca e ing capabil-
i y o LEDs and i makes he spa ial colo dis ibu ion
much la e han hose wi hou LaTb. In o he wo ds,
he sca e ed ligh is able o mo e in many di e en di-
ec ions as he concen a ion o LaTb pa icles pumped
in o yellow YAG:Ce phospho inc eases.
Besides inspec ing he in luence o LaTb concen a-
ion, his s udy also ocuses on in es iga ing he impac
o LaTb pa icle adius on he colo uni o mi y o he
in-cup package MCW-LEDs. The LaTb pa icle a-
dius anging om 1 o 10 µm is su eyed and analyzed
o di e en concen a ion o LaTb pa icles. Wi h he
small pa icle sizes om 1 µm o 4 µm, he CCT de i-
a ion o whi e LEDs, which is shown in Fig. 3, apidly
dec eases a a ound 500 K as he LaTb pa icle con-
cen a ion inc eases. Conside ing hese ac s, i can
be deduced ha he small pa icles could sca e mo e
ligh wi hin he wide iewing angle. As o he g ea e
size ange 5–10 µm, he endency o cu es exp essed
by he colo uni o mi y is simila o he small pa icle
case.
This is associa ed wi h he ac ha he inciden
ligh ends o be sca e ed, and hence, he decay le el
o CCT de ia ion o hese la ge pa icles is slowe
han hose o small pa icles. Gene ally, a e adding
he new phospho LaTb in o YAG:Ce phospho , he
colo uni o mi y can inc ease signi ican ly. In pa icu-
la , LaTb pa icles can imp o e he colo uni o mi y o
LEDs o all pa icle sizes wi h ange wi hin 1–10 µm,
e en i he la ge pa icles a e employed as seen in Fig. 3.
Concen a ion (%)
0 0.5 1 1.5
Luminous Flux (lm)
600
800
1000
1200
1400
1600
1800
1 2 3 4 5 6 7 8 9 10
Fig. 4: The luminous lux o MCW-LEDs is a a e age CCT
7000 K wi h di e en LaTb pa icle sizes and concen-
a ions.
Fu he mo e, he simula ion esul s shown in Fig. 4
also demons a e ha LaTb pa icle size and weigh
pe cen age ha e a s ong impac on he lumen ou -
pu . The highe weigh pe cen age o he g een LaTb
phospho , he be e quali y o he g een ligh s, and
he highe luminous lux o whi e LED. To s udy o
he in luence o he LaTb weigh pe cen age on lumen
ou pu , we con inuously a ied he LaTb concen a ion
om 0 o 1.8 % o each ixed size in he simula ion p o-
cess. As shown in Fig. 4, as o 1–4 µm LaTb pa icles,
luminous lux signi ican ly ises wi h LaTb weigh pe -
cen om 0 % o 1.5 %. Ob iously, when he LaTb
pa icle size is small, he lumen ou pu will dec ease
because he unwan ed backwa d sca e ing has been
demons a ed in many p e ious pape s. I means ha
he e is mo e ligh apped inside a package and he
lumen ou pu escaping om ha . Howe e , mixing
he new LaTb phospho in o phospho laye , lumen
ou pu could o e come he es ic ion wi h he small
size o phospho pa icles and is apidly imp o ed o
achie e he bes luminous lux. Wi h his no el ea-
u e, he u iliza ion o LaTb phospho becomes one o
he mos p omising me hods o imp o ing he op i-
cal p ope ies o LEDs. Wi h pa icle sizes la ge han
5µm, he ligh ends o p opaga e s onge in he o -
wa d di ec ion and es ic s backwa d ligh abso p ion
o LED chips, he eby he luminous lux a la ge size
pa icles will be highe . Hence, a mix u e o LaTb
pa icles wi h di e en sizes and YAG:Ce phospho s
emendously imp o es he lumen ou pu o he in-cup
phospho package MCW-LEDs.
Acco dingly, LaTb g een phospho can be used o
yield highe lumen ou pu due o a supplemen o g een
ligh in MCW-LEDs. Howe e , he CRI alues can de-
c ease as inc easing LaTb concen a ion. I can be ob-
se ed ha wi h he inc easing luminous lux, he CRI
alue insigni ican ly dec eases in size anging om 6 o
8µm as shown in Fig. 5. The eason is ha in o de o
Concen a ion (%)
0 0.5 1 1.5
Colo Rende ing Index
45
50
55
60
65
70
1 2 3 4 5 6 7 8 9 10
Fig. 5: The Colo Rende ing Index (CRI) alue o MCW-LEDs
is a a e age CCT 7000 K wi h di e en LaTb pa icle
sizes and concen a ions.
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achie e be e CRI alues, LEDs mus ha e a b oade
sou ce spec um o espond, and hus, he e iciency o
whi e LED would be educed. In addi ion, one o he
mos impo an ac o s used o e alua e he colo qual-
i y o whi e LEDs is he CQS ac o , which is also in-
es iga ed in his s udy. This ac o is cha ac e ized by
he colo ideli y le el o MCW-LEDs and i is assessed
by some e ms o colo quali y including CRI, ch o-
ma ic disc imina ion, and obse e p e e ences (Da is
and Ohno 2010). In he simula ion esul s (see Fig. 6),
he e is a sligh lessening in CQS alues wi h concen-
a ion a ound 1.5 % and he pa icle 6–8 µm.
We ound ha he 1–4 µm LaTb pa icles show
g ea e pe o mance capabili y o lumen ou pu and
colo uni o mi y a e adop ing LaTb pa icles in o
phospho laye . Howe e , we conclude ha he mos
app op ia e a e phospho pa icles ha ing a size ange
om 6 o 8 µm and he concen a ion a ound 1.5 %.
The eason is ha colo uni o mi y and op imal lumen
ou pu can be achie ed o he low CRI, CQS alues in
he same size and concen a ion ange.
Concen a ion (%)
0 0.5 1 1.5
Colo Quali y Scale
50
55
60
65
70
1 2 3 4 5 6 7 8 9 10
Fig. 6: The Colo Quali y Scale (CQS) alue o MCW-LEDs
is a a e age CCT 7000 K wi h di e en LaTb pa icle
sizes and concen a ions.
4. Conclusion
In his a icle, a esea ch was conduc ed o ind ou he
impac o g een (La,Ce,Tb)PO4:Ce:Tb phospho pa -
icles wi h he a ious concen a ions and sizes on he
MCW-LED pe o mance including he 4CCT, lumi-
nous lux, CRI, and CQS. The ob ained esul s indi-
ca e ha he g een LaTb phospho can imp o e bo h
he colo uni o mi y and he lumen ou pu . The op-
imum LaTb concen a ion and size a e de e mined
o ob ain he lowes alue o he CCT de ia ion as
well as he highes luminous lux accompanying wi h
a negligible dec ease in CRI, CQS alues. In ac , he
ob ained CRI and CQS alues can insigni ican ly de-
c ease when applying a ound 1.5 % LaTb concen a-
ion and 6-8 µm pa icles. I could be concluded ha
by pumping a small amoun o LaTb phospho has he
concen a ion anging om 0–1.8 % and he pa icle
sizes om 6–8 µm, we can ob ain be e pe o mance
o whi e LEDs. The e o e, LaTb pa icles should be
a p io i ized solu ion o be chosen o imp o ing he
op ical p ope ies o MCW-LEDs.
Acknowledgmen
This esea ch is unded by Founda ion o Science and
Technology De elopmen o Ton Duc Thang Uni e -
si y (FOSTECT), websi e: h p:// os ec . d .
edu. n, unde G an FOSTECT.2017.BR.06.
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Abou Au ho s
Nguyen Thi Phuong THAO was bo n in Quang
Ngai p o ince, Vie nam. She g adua ed om he
Uni e si y o Technology, Ho Chi Minh ci y, Vie
Nam. She ecei ed he B.Eng. and M.Eng. deg ees
in au oma ic con ol Enginee ing in 2006 and 2009,
espec i ely. She eaches a he depa men o elec-
ical and elec onics enginee ing, Ton Duc Thang
uni e si y, Ho Chi Minh ci y, Vie nam. He esea ch
in e es s include au oma ic con ol sys em, in elligen
con ol sys em, adap i e con ol sys em, op imiza ion
o powe sys em, powe sys em ope a ion and con ol
and Renewable Ene gy.
Phan Xuan LE was bo n in Binh Dinh p o ince,
Vie nam. He has been wo king a he Facul y o
Elec ical and Elec onics Enginee ing, HCMC Uni-
e si y o Food Indus y. He ecei ed his Ph.D. deg ee
om Kunming Uni e si y o Science and Technology,
China in 2015. His esea ch in e es is powe sys em;
op oelec onics.
Le Van THO was bo n in Thanh Hoa p o ince,
Vie nam. He has been wo king a he Ins i u e o
T opical Biology, Vie nam Academy o Science and
Technology. He ecei ed his mas e deg ee om Ho
Chi Minh Ci y Uni e si y o Science, Vie nam in
2017. His esea ch in e es is ecological enginee ing,
op oelec onics.
Mi osla VOZNAK (bo n in 1971) is an Associa e
P o esso wi h he Depa men o Telecommunica-
ions, Technical Uni e si y o Os a a, Czech Republic
and o eign p o esso wi h Ton Duc Thang Uni e si y
in Ho Chi Minh Ci y, Vie nam. He ecei ed his Ph.D.
deg ee in elecommunica ions in 2002 a he Technical
Uni e si y o Os a a. He is a senio esea che in he
c
2017 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 895
APPLIED PHYSICS VOLUME: 15 |NUMBER: 5 |2017 |DECEMBER
Supe compu ing cen e IT4Inno a ions in Os a a,
Czech Republic, a membe o he Scien i ic Boa d o
Facul y o Elec ical Enginee ing and Compu e Sci-
ence, VSB–Technical Uni e si y o Os a a, edi o ial
boa ds o se e al jou nals and boa ds o in e na ional
con e ences. Topics o his esea ch in e es s a e IP
elephony, wi eless ne wo ks, speech quali y and
ne wo k secu i y.
Nguyen Doan Quoc ANH was bo n in Khanh
Hoa p o ince, Vie nam. He has been wo king a he
Facul y o Elec ical and Elec onics Enginee ing, Ton
Duc Thang Uni e si y. Quoc Anh ecei ed his PhD
deg ee om Na ional Kaohsiung Uni e si y o Applied
Sciences, Taiwan in 2014. His esea ch in e es is
op oelec onics (such as Mul i-chip whi e ligh LEDs,
ee- o m lens, op ical ma e ial).
c
2017 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 896