Effects of Green - Emitting Phosphor (La,Ce,Tb)PO4:Ce:Tb on Luminous Flux and Color Quality of White LED Lamps

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 c 2017 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 890 APPLIED PHYSICS VOLUME: 15 |NUMBER: 5 |2017 |DECEMBER 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 © 2015 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 2 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. c 2017 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 891 APPLIED PHYSICS VOLUME: 15 |NUMBER: 5 |2017 |DECEMBER 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. c 2017 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 892 APPLIED PHYSICS VOLUME: 15 |NUMBER: 5 |2017 |DECEMBER 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. c 2017 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 893 APPLIED PHYSICS VOLUME: 15 |NUMBER: 5 |2017 |DECEMBER 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. 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Sca e ing e ec o SiO2pow- de s on co ela ed colo empe a u e uni o - mi y o mul i-chip whi e ligh LEDs. Jou nal o he Chinese Ins i u e o Enginee s. 2016, ol. 39, iss. 4, pp. 468–472. ISSN 0253-3839. DOI: 10.1080/02533839.2015.1117950. [15] DAVIS, W. and Y. OHNO. Colo quali y scale. Op ical enginee ing. 2010, ol. 49, iss. 3, pp. 288– 293. ISSN 1551-319X. DOI: 10.1117/1.3360335. 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