SiloleSilole Derivative Properties Derivative Properties in Organic Light Emitting in Organic Light Emitting

DiodesDiodesE. DuncanE. Duncan

MLKMLK HS Physics TeacherHS Physics Teacher

Mentors: Prof. Bernard Mentors: Prof. Bernard KippelenKippelen & Dr. Benoit & Dr. Benoit DomercqDomercq

OutlineOutline

IntroductionIntroductionTheoryTheoryMethodologyMethodologyResultsResultsConclusionConclusionAcknowledgementsAcknowledgementsReferencesReferences

IntroductionIntroduction

ObjectiveObjectiveDefinitionsDefinitions

What is an OLED?What is an OLED?What is a What is a SiloleSilole??

MotivationMotivation

ObjectiveObjective

Organic light emitting diodes (Organic light emitting diodes (OLEDOLED) were ) were fabricated using a new family of materials fabricated using a new family of materials based on based on silolesilole derivatives.derivatives.44

Si

XZ-I-125

Si

XZ-I-151

Si Ph

H

XZ-I-149B

Si

XZ-II-69

What is an OLED?What is an OLED?

OLEDsOLEDs, organic light emitting diodes, are solid, organic light emitting diodes, are solid--state devices state devices composed of thin films of organic molecules that create light composed of thin films of organic molecules that create light

with the application of with the application of electricityelectricity..11

They are practically the dynamic opposite of Solar Cells, They are practically the dynamic opposite of Solar Cells, which create electricity with the application of light.which create electricity with the application of light.

What is a What is a SiloleSilole??SilolesSiloles are a family of materials that have been are a family of materials that have been

found to have high external quantum efficiencies found to have high external quantum efficiencies and electron transport properties.and electron transport properties.44

MotivationMotivation

Provide brighter, crisper displays on electronic devicesProvide brighter, crisper displays on electronic devicesVery thin multilayer devices that do not require a backlightVery thin multilayer devices that do not require a backlightPrinted on plastic making displays flexible and lightweightPrinted on plastic making displays flexible and lightweightUse less power than conventional Use less power than conventional LEDsLEDs or or liquid crystal displaysliquid crystal displays ((LCDsLCDs) ) Much less costly to fabricate than traditional LCD displays Much less costly to fabricate than traditional LCD displays

http://www.universaldisplay.com/foled.htm http://www.engadget.com/entry/1234000980044037

TheoryTheory

Basic OLED StructureBasic OLED StructureHow an OLED worksHow an OLED works

Basic OLED StructureBasic OLED Structure

Multilayer device made up ofMultilayer device made up ofAnodeAnodeOrganic LayersOrganic LayersCathode Cathode

Organic Layers consist of Organic Layers consist of Hole Transport Layer (HTL) Hole Transport Layer (HTL) Electron Transport Layer (ETL)Electron Transport Layer (ETL)Emissive Layer (EL)Emissive Layer (EL)

AnodeHTLETLCathode

Light

Basic OLED Structure Basic OLED Structure (cont’d)(cont’d)

SubstrateSubstrateAnodeAnodeOrganic LayersOrganic Layers

Conducting LayersConducting LayersHTLHTLETLETL

Emissive Layer (EL)Emissive Layer (EL)

CathodeCathode

Substrate Substrate -- The substrate is made of glass and supports the The substrate is made of glass and supports the OLEDOLED..Anode Anode -- The anode removes electrons (adds electron "holes") when a curreThe anode removes electrons (adds electron "holes") when a current flows through the device. nt flows through the device. Conducting Conducting Layer(sLayer(s) ) -- One layer made of organic plastic molecules that transport "holeOne layer made of organic plastic molecules that transport "holes" from the anode. s" from the anode. ((HTLHTL) Another layer made of organic plastic molecules (different fr) Another layer made of organic plastic molecules (different from those in hole transport layer) that om those in hole transport layer) that transport electrons from the cathode. (transport electrons from the cathode. (ETLETL))Emissive Layer Emissive Layer –– This organic layer is where light is made. (EL)This organic layer is where light is made. (EL)Cathode Cathode -- The cathode injects electrons when a current flows through the dThe cathode injects electrons when a current flows through the device.evice.

http://science.howstuffworks.com/oled

How an OLED worksHow an OLED works

Holes are injected from the anode and Holes are injected from the anode and recombine with electrons injected from the recombine with electrons injected from the cathode creating an exciton which emits cathode creating an exciton which emits light when it relaxes to the ground state.light when it relaxes to the ground state.

Anode

Cathode

++ +

e-e-

HTLAnode

ETLEmission Layer

Hole Injection

Exciton

++ +

HTLAnode

ETLEmission Layer

Electron Injection

Hole Injection

Exciton

e-

hν

An An OLEDOLED device made out of the device made out of the silolesilole material presented in this study.material presented in this study.

Cathodes (5 devices)

Anode

MethodologyMethodology

Experimental ApparatusExperimental ApparatusDevice FabricationDevice FabricationMaterials UsedMaterials UsedOLED MeasurementsOLED Measurements

Experimental ApparatusExperimental Apparatus

Physical Vapor Deposition SystemPhysical Vapor Deposition SystemDoubleDouble--Glove Box SystemGlove Box System

Physical Vapor Deposition system with 4 low power sources to depPhysical Vapor Deposition system with 4 low power sources to deposit osit organic materials and 2 high power sources to deposit metalsorganic materials and 2 high power sources to deposit metals

A DoubleA Double--Glove Box System with a integrated spinGlove Box System with a integrated spin--coater to fabricate thin films coater to fabricate thin films from solutionfrom solution

Device FabricationDevice Fabrication

Nitrogen environmentNitrogen environmentLayers are deposited using spinLayers are deposited using spin--coating coating techniquestechniques

The material is sublimated and deposits evenly The material is sublimated and deposits evenly onto the substrateonto the substrate

Materials UsedMaterials UsedAnodeAnode:: indium tin oxide (ITO) 150 indium tin oxide (ITO) 150 nmnmOrganic layersOrganic layers::

HTL:HTL:aa copolymer based on copolymer based on NN--NN’’--diphenyldiphenyl--NN--NN’’ bis(3bis(3--methylphenyl)methylphenyl)--[1[1--11’’--biphenyl]biphenyl]--44--44’’--diaminediamine ((TPDTPD) 40 nm ) 40 nm ETLETL:: tristris--(8(8--hydroxyquinolinehydroxyquinoline) ) aluminum (aluminum (AlQAlQ33) 40 nm) 40 nmEL:EL: silolessiloles derivatives blended derivatives blended with polystyrene (4:1 weight with polystyrene (4:1 weight ratio) 40 nm ratio) 40 nm

CathodeCathode:: Lithium Fluoride (Lithium Fluoride (LiFLiF) 1 ) 1 nm and Aluminum 300 nmnm and Aluminum 300 nm

N N

N

NN

OO

OAl

TPD

AlQ3

OLED Measurements OLED Measurements

Voltage is applied to the deviceVoltage is applied to the deviceRecord current flowing through the deviceRecord current flowing through the deviceForward light output data is collectedForward light output data is collectedElectroluminescent spectrum is takenElectroluminescent spectrum is takenFrom this data, analysis can be done on the From this data, analysis can be done on the device performancedevice performance

ResultsResults

OLED AnalysisOLED AnalysisSpectrum of Spectrum of OLEDsOLEDs with with silolesilole derivatives in derivatives in Polystyrene (4:1 wtPolystyrene (4:1 wt--%)%)L, J, V characteristics as ELL, J, V characteristics as ELL, J, V characteristics as ETLL, J, V characteristics as ETLFindings & ExpectationsFindings & Expectations

OLED AnalysisOLED AnalysisCurrent DensityCurrent Density -- amount of current flowing per amount of current flowing per unit area (mA/cmunit area (mA/cm22))LuminescenceLuminescence -- accounts the photopic response of accounts the photopic response of the eye, the eye, the sensitivity response of the the sensitivity response of the photodetector photodetector and the physical geometry of the and the physical geometry of the measurement setmeasurement set--up (cd/mup (cd/m22) ) External Quantum EfficiencyExternal Quantum Efficiency -- the measurement the measurement of the number of photons emitted from the device of the number of photons emitted from the device in the forward direction divided by the number of in the forward direction divided by the number of electrons injected into the device (%)electrons injected into the device (%)

Spectrum of Spectrum of OLEDsOLEDs with with silolesilolederivatives in Polystyrene (4:1 wtderivatives in Polystyrene (4:1 wt--%)%)

400 450 500 550 600 650 7000.0

0.2

0.4

0.6

0.8

1.0 XZ-III-28 XZ-VI-96 XZ-I-151 XZ-I-149d XZ-I-125 Alq3

public\shared\OLED\Siloles\AH-IV-7\spectrumAH-IV-7

Ele

ctro

lum

ines

cenc

e (a

.u.)

Wavelength (nm)

EL spectrum of Silole derivatives

400 450 500 550 600 650 7000.0

0.2

0.4

0.6

0.8

1.0

XZ-III-28 XZ-VI-96 XZ-I-151 XZ-I-149d XZ-I-125

public\shared\OLED\Siloles\AH-IV-7\spectrumAH-IV-14

Ele

ctro

lum

ines

cenc

e (a

.u.)

Wavelength (nm)

EL spectrum of Silole derivatives

Alq3 (40 nm)Silole:PS (40 nm)Poly-TPD-MeO2 (35 nm)

ITOGlass

Al (200 nm)LiF (1 nm)

Emission layer configuration (EL)

Silole:PS (40 nm)Poly-TPD-MeO2 (35 nm)

ITOGlass

Al (200 nm)LiF (1 nm)

Electron transport layer configuration (ETL)

L, J, V characteristics as ELL, J, V characteristics as EL

-2 0 2 4 6 8 10 12 14 161E-81E-71E-61E-51E-41E-30.010.1

110

1001000

XZ-III-28 XZ-VI-96 XZ-I-151 XZ-I-149d XZ-I-125

public\shared\OLED\Siloles\AH-IV-7\AH-IV-7

J-V characteristics of different siloles as EL

AH-IV-7

Cur

rent

Den

sity

(mA

/cm

2 )

Applied Voltage (V)

0

1

2

3

4

5

6

7

8

9

-2 0 2 4 6 8 10 12 14 161E-3

0.01

0.1

1

10

100

1000

10000

public\shared\OLED\Siloles\AH-IV-7\AH-IV-7AH-IV-7

Lum

inan

ce (c

d/m

2 )

Applied Voltage (V)

XZ-III-28 XZ-VI-96 XZ-I-151 XZ-I-149d XZ-I-125

L-V & EQE-V characteristics of different siloles as EL

Ext. Q

uantum E

fficiency (%)

L, J, V characteristics as ETLL, J, V characteristics as ETL

-2 0 2 4 6 8 10 12 14 16 18 201E-81E-71E-61E-51E-41E-30.010.1

110

1001000

XZ-III-28 XZ-VI-96 XZ-I-151 XZ-I-149b XZ-I-125

public\shared\OLED\Siloles\AH-IV-14\AH-IV-14

J-V characteristics of different siloles as ETL

AH-IV-14

Cur

rent

Den

sity

(mA

/cm

2 )

Applied Voltage (V)

0

1

2

3

4

5

6

7

8

9

-2 0 2 4 6 8 10 12 14 16 18 201E-3

0.01

0.1

1

10

100

1000

10000

public\shared\OLED\Siloles\AH-IV-14\AH-IV-14AH-IV-14

Lum

inan

ce (c

d/m

2 )

Applied Voltage (V)

XZ-III-28 XZ-VI-96 XZ-I-151 XZ-I-149b XZ-I-125

L-V & EQE-V characteristics of different siloles as ETL

Ext. Q

uantum E

fficiency (%)

Findings & ExpectationsFindings & Expectations

Current density, luminance, and external Current density, luminance, and external quantum efficiency were observed.quantum efficiency were observed.

Although the emission layer configuration (EL) Although the emission layer configuration (EL) efficiency was minutely greater than that of the efficiency was minutely greater than that of the electron transport layer configuration (ETL), the electron transport layer configuration (ETL), the results were essentially the same for both.results were essentially the same for both.

The efficiency was between 1 and 3% for both The efficiency was between 1 and 3% for both configurations.configurations.

ConclusionConclusion

Found that OLED testing is very rigorous & Found that OLED testing is very rigorous & detailed workdetailed workNot easy to find high efficiency (> 3%)Not easy to find high efficiency (> 3%)Higher efficiency with blue light emission is Higher efficiency with blue light emission is important future goalimportant future goalGood results in future very possible since this Good results in future very possible since this research team is dedicated, diligent, persistent, research team is dedicated, diligent, persistent, and supportive of one anotherand supportive of one another

AcknowledgementsAcknowledgements

Prof. Bernard Prof. Bernard KippelenKippelen, Professor, ProfessorDr. Benoit Dr. Benoit DomercqDomercq, Research Scientist, Research ScientistAndreas Andreas HaldiHaldi, Graduate Research Assistant, Graduate Research AssistantThe Remainder of the The Remainder of the KippelenKippelen Research Research Group of the Georgia Tech School of Group of the Georgia Tech School of Electrical and Computer EngineeringElectrical and Computer Engineering

The The KippelenKippelen Research Group Research Group

Acknowledgements Acknowledgements (cont’d)(cont’d)

Doctors Edward and Doctors Edward and LeylaLeyla Conrad, StepConrad, Step--UpUpGeorgia Institute of TechnologyGeorgia Institute of TechnologyNational Science Foundation National Science Foundation

ReferencesReferences

1.1. http://http://science.howstuffworks.com/oled.htmscience.howstuffworks.com/oled.htm2.2. http://http://en.wikipedia.org/wiki/oleden.wikipedia.org/wiki/oled3.3. 1, 11, 1--DiphenylDiphenyl--2,3,4,52,3,4,5--tetrakis(9,9tetrakis(9,9--dimethylfluorendimethylfluoren--

22--yl)silole Properties in Organic Lightyl)silole Properties in Organic Light--Emitting Emitting Diodes and OrganicDiodes and Organic--Field Effect Field Effect Transistors,SarahTransistors,SarahMontgomery, Purdue University, Bernard Montgomery, Purdue University, Bernard KippelenKippelen, , Benoit Benoit DomercqDomercq School of Electrical & Computer School of Electrical & Computer Engineering, Georgia Tech, 2006Engineering, Georgia Tech, 2006

4.4. Chen, H. Y.; et al. Chen, H. Y.; et al. ApplAppl. Phys. . Phys. LettLett. 2002, 81, (4), . 2002, 81, (4), 574574--576.576.