Research Article Enhancement and Quenching of Fluorescence ... · e silver nanoparticles (SNPs) layer was incorporated as an interlayer between the electron-transport layer and theelectrode,whichcanimprovethee

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2013 Article ID 841436 5 pageshttpdxdoiorg1011552013841436

Research ArticleEnhancement and Quenching of Fluorescence by SilverNanoparticles in Organic Light-Emitting Diodes

Ying-Chung Chen1 Chia-Yuan Gao1 Kan-Lin Chen2

Teen-Hang Meen3 and Chien-Jung Huang4

1 Department of Electrical Engineering National Sun Yat-sen University Kaohsiung 80424 Taiwan2Department of Electronic Engineering Fortune Institute of Technology Kaohsiung 83160 Taiwan3Department of Electronic Engineering National Formosa University Hu-Wei Yunlin 63201 Taiwan4Department of Applied Physics National University of Kaohsiung Kaohsiung 81148 Taiwan

Correspondence should be addressed to Kan-Lin Chen klchenfotechedutw and Chien-Jung Huang chiennukedutw

Received 8 November 2013 Accepted 14 November 2013

Academic Editor Liang-Wen Ji

Copyright copy 2013 Ying-Chung Chen et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

The influence of silver nanoparticles (SNPs) on the performance of organic light-emitting diodes (OLEDs) is investigated in thisstudyThe SNPs are introduced between the electron-transport layers by means of thermal evaporation SNPs are found to have thesurface plasmon resonance at wavelength 525 nm when the mean particle size of SNPs is 34 nmThe optimized OLED in terms ofthe spacing between the emitting layer and SNPs is found to have the maximum luminance 24 times higher than that in the OLEDwithout SNPs The energy transfer between exciton and surface plasmons with the different spacing distances has been studied

1 Introduction

The organic light-emitting diode (OLED) has displayedsignificant potentiality in the applications of flat panel displayand lighting which is mainly because of its low power con-sumption Various means have been developed to optimizeOLEDrsquos efficiency for example doping the hole-transportingmaterials or inserting the hole-blocking layer to decrease holemobility and balance holeelectrons ratio in emitting layer(EML) of device [1ndash3] doping phosphorescence materialinto the EML to increase the quantum efficiency by takingadvantage of triplet state recombination [4ndash6] or improvingthe holeelectron balance by increasing electron injection[7 8] However those methods increased the complexity ofdevice structure which increases the fabrication time and costof device

Recently in view of the luminance enhancement effect ofsurface plasmon (SP) the surface plasmon resonance effect(SPRE) of metal nanoparticles has been actively studied inboth OLED and inorganic light-emitting diode in [9ndash12]It is well known that the SPRE was induced by interaction

between the surface charge of metal and the electromagneticfield of the incident light [13] When the metal surface isclose to the fluorescent molecule the luminous efficiencyof the fluorescent molecule can be significantly enhancedNevertheless the nonradiative quenching of exciton at themetal surface occurs when the distance is much smallerbetween the fluorescent molecule and the metal surfaceTherefore two competitive processes take place in an exciton-SP system (i) increase in radiative intensity by subtractionin decay time of exciton and (ii) nonradiative quenching ofexciton by energy transfer to the metal surface Thereforethe distances between the fluorescent molecule and the metalsurface are a very important parameter in terms of thecoupling between the SPs and excitons

The silver nanoparticles (SNPs) layer was incorporatedas an interlayer between the electron-transport layer andthe electrode which can improve the efficiency of OLEDs[14] Nevertheless the causes of nonradiative quenching andefficiency improvement at different distances between thesilver nanoparticles and electron-transport layer were notdescribed in detail In this paper the distance of the SNPs

2 Journal of Nanomaterials

Al

LiF (05nm)BPhen (13 minus xnm)

SNCsBPhen (xnm)

NPB (35nm)

ITO

Substrate (glass)

Alq3

(40nm)

Figure 1 Schematic structure of OLED with different spacingdistances between EML and SNPs

from the EML has been optimized for enhancement ofmaximum luminescence and how the distances between theSNPs and the EML influenced the enhancement of deviceluminescence was also observed Furthermore mechanismsof increase in radiative intensity and nonradiative quenchinghave been described in detail

2 Experimental

The schematic structure of OLEDs is shown in Figure 1Indium tin oxide (ITO) coated on glass with a sheet resistanceof 10Ωsq was used as the starting substrate The substratewas cleaned with acetone methanol and deionized waterand then dried with nitrogen gas After the cleaning processthe substrates were loaded into a thermal evaporator After-ward NN1015840-bis-(1-naphthyl)-NN-diphenyl-111015840-biphenyl1-4-diamine (NPB 35 nm) tris-(8-hydroxyquinoline) aluminum(Alq3 40 nm) 47-diphenyl-1-110-phenanthroline (BPhen

X nm) SNPs BPhen (13-X nm) lithium fluoride (LiF05 nm) and aluminum (Al 100 nm) were deposited NPBand BPhen were used as the hole and electron-transportlayers respectively Alq

3has been used as EML LiF Al and

ITO have been used as the electron-injection layer cathodeand anode respectively In addition the SNCswere fabricatedby thermal evaporation of silver slug The deposition rateand the deposition time are 001 nms and 300 secondsDuring the deposition the base pressure of the chamber wasmaintained at as low as 24 times 10minus6 Torr The active areaof the device was 6 times 6mm2 The deposition rates of allorganic materials were maintained at 001 nms except forthe Al whose deposition rate was 05 nms The thickness ofthe layers is controlled by using a quartz-crystal monitor inthis work The current density-voltage (J-V) and luminance-voltage (L-V) characteristics of the devices were measuredby using a Keithley 2400 (Keithley Instruments Inc USA)and a PR-655 (Photo Research Inc USA) respectivelyThe absorption spectrum was measured by using a U-3900spectrophotometer (Hitachi Japan) The photoluminescence(PL) spectrum and scanning electron microscope (SEM)images were measured by using an IK series (Kimmon Koha

20 25 30 35 40 450

5

10

15

20

25

Size

dist

ribut

ion

()

Size (nm)

100nm

(a)

400 450 500 550 60000

02

04

06

08

10

Absorption spectrum of SNCs

Abso

rptio

n (a

u)

Wavelength (nm)350 650

00

02

04

06

08

10

PL spectrum of

Em

issio

n in

tens

ity (a

u)

Alq3

(b)

Figure 2 (a) SEM image of the SNPs on the glass surface (b)Absorption spectrum of the SNPs and PL spectrum of the Alq

3

Japan) and a JSM-6700F (JEOL Japan) All measurementswere made at room temperature under ambient air

3 Results and Discussion

Figure 2(a) shows the SEM image of SNPs on a glass substrateThe mean particle size of SNPs in Figure 2(a) was calculatedand found to be 34 nm In addition the size distribution ofthe SNCs is plotted in the inset of Figure 2(a) It is observedthat the size distribution of the SNCs is from 21 to 45 nmThe absorption spectrum of SNPs with amean particle size of34 nm and the PL spectrum of Alq

3are shown in Figure 2(b)

It is observed that the absorption spectrum of SNPs witha mean particle size of 34 nm is about 525 nm and the PLspectrum of Alq

3is about 523 nm Furthermore it can be

seen that there is a significant overlap between the absorptionspectrum of the SNPs and PL spectrum of Alq

3 It is well

known that the excellent overlap between the two spectrasuggests that they can be used for SP-exciton coupling Inother words this overlap implied that these SNPs can be usedto increase the characters of OLEDs

Journal of Nanomaterials 3

0 2 4 6 8 10 120

100

200

300

400

Voltage (V)

Curr

ent d

ensit

y (m

Ac

m2)

Without AgWith Ag and x = 13nmWith Ag and x = 10nm

With Ag and x = 7nmWith Ag and x = 4nmWith Ag and x = 0nm

(a)

2 4 6 8 10 120

2000

4000

6000

8000

10000

12000

14000

Voltage (V)

Lum

inan

ce (c

dm

2)



(b)

Figure 3 (a) Current density-voltage curves and (b) luminance-voltage curves of OLEDs with and without SNPs

2 4 6 8 10 120

5000

10000

15000

20000

25000

30000

35000

Inte

nsity

(cps

)

Depth (nm)

ITOSubstrate (glass)

(I)

Silver SNPs

Alq3

layer

Alq3

(15nm)

(a)

3 6 9 12 15 18 210

5000

10000

15000

20000

25000

30000

35000

Inte

nsity

(cps

)

Depth (nm)

BPhen layer


(II)

SNPs

Silver

Alq3

layer

Alq3

(15nm)BPhen (13nm)

(b)

Figure 4 XPS depth profile of silver from the (a) structure I and (b) structure II

The distance between the fluorescent molecule and theSNPs is a very important parameter in terms of the cou-pling between the SPs and excitons Therefore the distancewas tuned by changing the thickness of the spacing layer(BPhen) The J-V curves of the devices without SNPs andwith different spacing distances between EML and SNPs areplotted in Figure 3(a) It can be clearly seen that the currentdensity of the devices with SNPs at thickness of spacing≧7 nm is higher than that of devices without SNPs becausethe localized electric field around the SNPs is enhancedresulting in an increase in electron injection from cathodeelectrode Figure 3(b) shows the L-V characteristic of thedevices without SNPs and with different spacing distancesbetween EML and SNPs It is observed that the luminanceof the devices was increased with a decrease in thickness ofthe spacing layer in the condition of thickness of spacing≧7 nm because the surface-plasmon-enhanced spontaneous

emission rate of SNPs is enhanced when the SNPs are closeto the EML In addition the luminance of the device withouta spacing layer is quite low compared with that of the devicewithout SNPs because the SNPs will penetrate considerablyinto EML

To further confirm the relationship between the penetra-tion of the SNPs and the luminance of the device the X-rayphotoelectron spectrometry (XPS) depth profile of silver ismeasured in this paperThe samples for analysis of XPS depthprofile are prepared as follows (I) ITOAlq

3(15 nm)SNPs

and (II) ITOAlq3(15 nm)BPhen (13 nm)SNPs Figures 4(a)

and 4(b) show the XPS depth profile of silver from structuresI and II respectively Structures I and II are plotted in theinset of Figures 3(a) and 3(b) respectively It can be clearlyseen that the intensity of the SNPs into the EML of thestructure II is quite low compared with that of structure Ibecause structure II has a spacing layer which can impede


HOMO

Electron transfer

SNP

LUMO

Alq3 EF

Figure 5 Schematic diagram of emission quenching process

0 2 4 6 8 10 1200

05

10

15

20

25

Enhancement factorenergy transfer efficiency

Enha

ncem

ent f

acto

r

0

20

40

60

80

100

X (nm)

Fo

rste

r

Forster

ener

gy tr

ansfe

r effi

cien

cy (

)

Figure 6 Enhancement factor and Forster energy transfer efficiencyfor different spacing distances between EML and SNPs

the SNPs penetration into EML Moreover the emissionquenching was caused when the SNPs penetrated into EMLThe schematic diagram of the emission quenching process isshown in Figure 5 The emission quenching mainly resultedfrom the electron transfer from the lowest unoccupiedmolec-ular orbital (LUMO) of Alq

3to the Fermi level of the SNPs

Furthermore the exciton is unable to be generated when theelectron transfers from the LUMO of Alq

3to the Fermi level

of the SNPs [15] Therefore when the SNPs penetrated intoAlq3 the emission quenching of the device was caused The

enhancement and quenching of the device are a consequenceof the interplay between the increase in radiative intensityby SPRE of SNPs and the emission quenching by electrontransfer from the Alq

3to the SNPs

Figure 6 shows the plots of the enhancement factor andthe Forster energy transfer efficiency as a function of the

spacing distance The enhancement factor is expressed as11987121198711 where 119871

2is the maximum luminance of the device

with SNPs and 1198711is the maximum luminance of the device

without SNPs It is observed that the enhancement factorswere increased with a decrease in thickness of the spacinglayer in the condition of thickness of spacing ≧7 nm becausethe surface-plasmon-enhanced spontaneous emission rate ofSNPs is enhanced when the SNPs are close to the EMLFurthermore when the SNPs are close to the fluorescentmolecule the localized electric field around the SNPs isenhanced resulting in an increase in electron injection fromcathode electrode In addition the enhancement factors weredecreased with a decrease in thickness of the spacing layerin the condition of thickness of spacing lt7 nm because theamounts of SNPs penetration into EML are of considerableenhancement resulting in the emission quenching of thedevice It is also observed that the maximum enhancementfactor is obtained when the Forster energy transfer efficiencyis 50 The relationship between the Forster energy transferefficiency and the spacing distance can be expressed asfollows [16]

119864 =1

1 + (1198771198770)6 (1)

where 119864 is the Forster energy transfer efficiency 119877 is thespacing distance between the EML and SNPs and 119877

0is

the Forster radius The formula can clearly illustrate thatthe Forster energy transfer efficiency is enhanced with adecrease in the spacing distance between the EML and SNPsMoreover the Forster energy transfer efficiency of 50 isobtained when the spacing distance is equal to the Forsterradius The Forster radius can be expressed as follows [17]

1198770= 0211(120601

0119899minus41198691198962)16

(2)

where 1198770is the Forster radius 120601

0is the quantum yield of

donor 119899 is the refractive index of the medium 119869 is thenormalized overlap integral of the donor and the acceptorspectra and 119896 is the orientation of the dipoles Thereforethe Forster radius is calculated as 7 nm by using (2) Inaddition the enhancement factor of the device without aspacing layer is quite low compared with that of the devicewith a spacing layer because the device without a spacinglayer has an energy transfer of 100 from the fluorescentmolecule to the SNPs resulting in considerable nonradia-tive quenching of exciton The schematic diagram of thenonradiative decay process of exciton is shown in Figure 7The nonradiative decay process of exciton will be causedbecause of the excitation of surface plasmon polaritonmodeswhich propagate along the surface of the SNPs Moreoverthe excitation of surface plasmon polariton modes results inan extra nonradiative decay channel at the interface betweenthe fluorescent molecule and the SNPs [18] Therefore whenthe SNPs are very close to the fluorescent molecule the SNPswill not only penetrate considerably into the EML but alsogenerate an extra nonradiative decay channel


(Radiative decay)

Excited state

Ground state

SNP

(Nonradiative decay channel)

Excitation

Alq3

+ minus

+ minus

+ minus

+ minus

+ minus

+ minus

+ minus

+ minus

Figure 7 Schematic diagram of the nonradiative decay process ofexciton

4 Conclusion

In summary the SNPs are introduced between the electron-transport layers and their best performance is found to havethe maximum luminance 24 times higher than the OLEDwithout SNPs when the spacing distance is 7 nm When theSNPs are close to the fluorescent molecule the SNPs willcreate two advantages (i) they will enhance the spontaneousrecombination of excitons due to the subtraction in theexciton lifetime and (ii) they will enhance the electroninjection because of SPRE which will induce the enhancedlocalized electric field around the SNPs Nevertheless whenthe SNPs are very close to the fluorescent molecule the SNPscontrarily will result in two disadvantages (i) they will pen-etrate considerably into the EML resulting in the emissionquenching of the device because the electron transfers fromthe LUMOofAlq

3to the Fermi level of the SNPs and (ii) they

will cause the nonradiative decay process of exciton becausethe excitation of surface plasmon polariton modes results inan extra nonradiative decay channel at the interface betweenthe fluorescent molecule and the SNPs

Acknowledgment

This work was partially supported by the National ScienceCouncil of Taiwan (NSCT) under Contract no NSC102-2221-E-390-019-MY2

References

[1] Y Zhao L Duan D Zhang et al ldquoSmall molecular phospho-rescent organic light-emitting diodes using a spin-coated holeblocking layerrdquo Applied Physics Letters vol 100 no 8 ArticleID 083304 4 pages 2012

[2] K Narayan S Varadarajaperumal G Mohan Rao M ManorVarma and T Srinivas ldquoEffect of thickness variation of holeinjection and hole blocking layers on the performance of flu-orescent green organic light emitting diodesrdquo Current AppliedPhysics vol 13 no 1 pp 18ndash25 2013

[3] J Wang J Liu S Huang et al ldquoHigh efficiency green phospho-rescent organic light-emitting diodes with a low roll-off at highbrightnessrdquo Organic Electronics vol 14 no 11 pp 2854ndash28582013

[4] S J Lee J H Seo J H Kim et al ldquoEfficient triplet excitonconfinement of white organic light-emitting diodes using aheavily doped phosphorescent blue emitterrdquo Thin Solid Filmsvol 518 no 22 pp 6184ndash6187 2010

[5] Y Zhang M Slootsky and S R Forrest ldquoEnhanced efficiencyin high-brightness fluorescent organic light emitting diodesthrough triplet managementrdquo Applied Physics Letters vol 99no 22 Article ID 223303 3 pages 2011

[6] C YunG Xie CMurawski et al ldquoUnderstanding the influenceof doping in efficient phosphorescent organic light-emittingdiodes with an organic p-i-n homojunctionrdquo Organic Electron-ics vol 14 no 7 pp 1695ndash1703 2013

[7] Y W Park J H Choi T H Park et al ldquoRole of n-dopantbased electron injection layer in n-doped organic light-emittingdiodes and its simple alternativerdquo Applied Physics Letters vol100 no 1 Article ID 013312 4 pages 2012

[8] K KimKHong I Lee S Kim and J L Lee ldquoElectron injectionin magnesium-doped organic light-emitting diodesrdquo AppliedPhysics Letters vol 101 no 14 Article ID 141102 4 pages 2012

[9] C-Y Cho S-J Lee J-H Song et al ldquoEnhanced optical outputpower of green light-emitting diodes by surface plasmon of goldnanoparticlesrdquo Applied Physics Letters vol 98 no 5 Article ID051106 3 pages 2011

[10] F Liu and J M Nunzi ldquoEnhanced organic light emitting diodeand solar cell performances using silver nano-clustersrdquoOrganicElectronics vol 13 no 9 pp 1623ndash13632 2012

[11] Y Xiao J P Yang P P Cheng et al ldquoSurface plasmon-enhanced electroluminescence in organic light-emitting diodesincorporating Au nanoparticlesrdquo Applied Physics Letters vol100 no 1 Article ID 013308 4 pages 2012

[12] K-C Tien M-S Lin Y-H Lin et al ldquoUtilizing surfaceplasmonpolaritonmediated energy transfer for tunable double-emitting organic light-emitting devicesrdquo Organic Electronicsvol 11 no 3 pp 397ndash406 2010

[13] W L Barnes A Dereux and T W Ebbesen ldquoSurface plasmonsubwavelength opticsrdquo Nature vol 424 no 6950 pp 824ndash8302003

[14] A Kumar R Srivastava P Tyagi D S Mehta and M NKamalasanan ldquoEfficiency enhancement of organic light emit-ting diode via surface energy transfer between exciton andsurface plasmonrdquoOrganic Electronics vol 13 no 1 pp 159ndash1652012

[15] Y-P Hsieh C-T Liang Y-F Chen C-W Lai and P-T ChouldquoMechanism of giant enhancement of light emission from AuCdSe nanocompositesrdquo Nanotechnology vol 18 no 41 ArticleID 415707 4 pages 2007

[16] C S YunA Javier T Jennings et al ldquoNanometal surface energytransfer in optical rulers breaking the FRET barrierrdquo Journalof the American Chemical Society vol 127 no 9 pp 3115ndash31192005

[17] X Zhang C A Marocico M Lunz et al ldquoWavelengthconcentration and distance dependence of nonradiative energytransfer to a plane of gold nanoparticlesrdquo ACS Nano vol 6 no10 pp 9283ndash9290 2012

[18] G W Ford and W H Weber ldquoElectromagnetic interactions ofmolecules with metal surfacesrdquo Physics Reports vol 113 no 4pp 195ndash287 1984

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CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


Al

LiF (05nm)BPhen (13 minus xnm)

SNCsBPhen (xnm)

NPB (35nm)

ITO

Substrate (glass)

Alq3

(40nm)

Figure 1 Schematic structure of OLED with different spacingdistances between EML and SNPs

from the EML has been optimized for enhancement ofmaximum luminescence and how the distances between theSNPs and the EML influenced the enhancement of deviceluminescence was also observed Furthermore mechanismsof increase in radiative intensity and nonradiative quenchinghave been described in detail

2 Experimental

The schematic structure of OLEDs is shown in Figure 1Indium tin oxide (ITO) coated on glass with a sheet resistanceof 10Ωsq was used as the starting substrate The substratewas cleaned with acetone methanol and deionized waterand then dried with nitrogen gas After the cleaning processthe substrates were loaded into a thermal evaporator After-ward NN1015840-bis-(1-naphthyl)-NN-diphenyl-111015840-biphenyl1-4-diamine (NPB 35 nm) tris-(8-hydroxyquinoline) aluminum(Alq3 40 nm) 47-diphenyl-1-110-phenanthroline (BPhen

X nm) SNPs BPhen (13-X nm) lithium fluoride (LiF05 nm) and aluminum (Al 100 nm) were deposited NPBand BPhen were used as the hole and electron-transportlayers respectively Alq

3has been used as EML LiF Al and

ITO have been used as the electron-injection layer cathodeand anode respectively In addition the SNCswere fabricatedby thermal evaporation of silver slug The deposition rateand the deposition time are 001 nms and 300 secondsDuring the deposition the base pressure of the chamber wasmaintained at as low as 24 times 10minus6 Torr The active areaof the device was 6 times 6mm2 The deposition rates of allorganic materials were maintained at 001 nms except forthe Al whose deposition rate was 05 nms The thickness ofthe layers is controlled by using a quartz-crystal monitor inthis work The current density-voltage (J-V) and luminance-voltage (L-V) characteristics of the devices were measuredby using a Keithley 2400 (Keithley Instruments Inc USA)and a PR-655 (Photo Research Inc USA) respectivelyThe absorption spectrum was measured by using a U-3900spectrophotometer (Hitachi Japan) The photoluminescence(PL) spectrum and scanning electron microscope (SEM)images were measured by using an IK series (Kimmon Koha

20 25 30 35 40 450

5

10

15

20

25

Size

dist

ribut

ion

()

Size (nm)

100nm

(a)

400 450 500 550 60000

02

04

06

08

10

Absorption spectrum of SNCs

Abso

rptio

n (a

u)

Wavelength (nm)350 650

00

02

04

06

08

10

PL spectrum of

Em

issio

n in

tens

ity (a

u)

Alq3

(b)

Figure 2 (a) SEM image of the SNPs on the glass surface (b)Absorption spectrum of the SNPs and PL spectrum of the Alq

3

Japan) and a JSM-6700F (JEOL Japan) All measurementswere made at room temperature under ambient air

3 Results and Discussion

Figure 2(a) shows the SEM image of SNPs on a glass substrateThe mean particle size of SNPs in Figure 2(a) was calculatedand found to be 34 nm In addition the size distribution ofthe SNCs is plotted in the inset of Figure 2(a) It is observedthat the size distribution of the SNCs is from 21 to 45 nmThe absorption spectrum of SNPs with amean particle size of34 nm and the PL spectrum of Alq

3are shown in Figure 2(b)

It is observed that the absorption spectrum of SNPs witha mean particle size of 34 nm is about 525 nm and the PLspectrum of Alq

3is about 523 nm Furthermore it can be

seen that there is a significant overlap between the absorptionspectrum of the SNPs and PL spectrum of Alq

3 It is well

known that the excellent overlap between the two spectrasuggests that they can be used for SP-exciton coupling Inother words this overlap implied that these SNPs can be usedto increase the characters of OLEDs


0 2 4 6 8 10 120

100

200

300

400

Voltage (V)

Curr

ent d

ensit

y (m

Ac

m2)



(a)

2 4 6 8 10 120

2000

4000

6000

8000

10000

12000

14000

Voltage (V)

Lum

inan

ce (c

dm

2)



(b)


2 4 6 8 10 120

5000

10000

15000

20000

25000

30000

35000

Inte

nsity

(cps

)

Depth (nm)


(I)

Silver SNPs

Alq3

layer

Alq3

(15nm)

(a)

3 6 9 12 15 18 210

5000

10000

15000

20000

25000

30000

35000

Inte

nsity

(cps

)

Depth (nm)

BPhen layer


(II)

SNPs

Silver

Alq3

layer

Alq3

(15nm)BPhen (13nm)

(b)





3(15 nm)SNPs




HOMO

Electron transfer

SNP

LUMO

Alq3 EF


0 2 4 6 8 10 1200

05

10

15

20

25


Enha

ncem

ent f

acto

r

0

20

40

60

80

100

X (nm)

Fo

rste

r

Forster

ener

gy tr

ansfe

r effi

cien

cy (

)





3to the Fermi level



3to the SNPs






119864 =1

1 + (1198771198770)6 (1)


0is


1198770= 0211(120601

0119899minus41198691198962)16

(2)





(Radiative decay)

Excited state

Ground state

SNP


Excitation

Alq3

+ minus

+ minus

+ minus

+ minus

+ minus

+ minus

+ minus

+ minus


4 Conclusion




Acknowledgment


References


























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 2 4 6 8 10 120

100

200

300

400

Voltage (V)

Curr

ent d

ensit

y (m

Ac

m2)



(a)

2 4 6 8 10 120

2000

4000

6000

8000

10000

12000

14000

Voltage (V)

Lum

inan

ce (c

dm

2)



(b)


2 4 6 8 10 120

5000

10000

15000

20000

25000

30000

35000

Inte

nsity

(cps

)

Depth (nm)


(I)

Silver SNPs

Alq3

layer

Alq3

(15nm)

(a)

3 6 9 12 15 18 210

5000

10000

15000

20000

25000

30000

35000

Inte

nsity

(cps

)

Depth (nm)

BPhen layer


(II)

SNPs

Silver

Alq3

layer

Alq3

(15nm)BPhen (13nm)

(b)





3(15 nm)SNPs




HOMO

Electron transfer

SNP

LUMO

Alq3 EF


0 2 4 6 8 10 1200

05

10

15

20

25


Enha

ncem

ent f

acto

r

0

20

40

60

80

100

X (nm)

Fo

rste

r

Forster

ener

gy tr

ansfe

r effi

cien

cy (

)





3to the Fermi level



3to the SNPs






119864 =1

1 + (1198771198770)6 (1)


0is


1198770= 0211(120601

0119899minus41198691198962)16

(2)





(Radiative decay)

Excited state

Ground state

SNP


Excitation

Alq3

+ minus

+ minus

+ minus

+ minus

+ minus

+ minus

+ minus

+ minus


4 Conclusion




Acknowledgment


References


























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




HOMO

Electron transfer

SNP

LUMO

Alq3 EF


0 2 4 6 8 10 1200

05

10

15

20

25


Enha

ncem

ent f

acto

r

0

20

40

60

80

100

X (nm)

Fo

rste

r

Forster

ener

gy tr

ansfe

r effi

cien

cy (

)





3to the Fermi level



3to the SNPs






119864 =1

1 + (1198771198770)6 (1)


0is


1198770= 0211(120601

0119899minus41198691198962)16

(2)





(Radiative decay)

Excited state

Ground state

SNP


Excitation

Alq3

+ minus

+ minus

+ minus

+ minus

+ minus

+ minus

+ minus

+ minus


4 Conclusion




Acknowledgment


References


























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(Radiative decay)

Excited state

Ground state

SNP


Excitation

Alq3

+ minus

+ minus

+ minus

+ minus

+ minus

+ minus

+ minus

+ minus


4 Conclusion




Acknowledgment


References


























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



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Research Article Enhancement and Quenching of Fluorescence ... · e silver nanoparticles (SNPs) layer was incorporated as an interlayer between the electron-transport layer and theelectrode,whichcanimprovethee