Thermal conductivity of organic semi Thermal conductivity of organic - - PowerPoint PPT Presentation

Thermal conductivity of organic semi Thermal conductivity of organic semi-

• conducting materials using 3 omega and

conducting materials using 3 omega and conducting materials using 3 omega and conducting materials using 3 omega and radiothermal radiothermal photometry techniques photometry techniques

• F. Reisdorffer1, N. Horny2, B. Garnier3 ,C. Renaud4, M. Chirtoc2, T.P. Nguyen1

2Laboratoire GRESPI 1Institut des Matériaux Jean Rouxel 3Laboratoire de Thermocinétique 4Laboratoire LAPLACE

Reims Nantes

3rd European Energy Conference , Budapest Oct 27‐30 2013

Toulouse Nantes

Context PTR 3 ω Comparison Conclusion Flexible transparent electronic market Monitoring Emerging devices OLEDs applications Car industry 2020 40 109 $ t 800 106 it Car industry

Flexible OLED market

2020: 40.109 $ et 800.106 units Lighting Lighting

http://www.ihs.com Aug 29th 2013

2

Context PTR 3 ω Comparison Conclusion Problematic Monitoring

High brightness Lighting g g

Lifetime decrease

g g

Hi h t d it Lifetime decrease J l ff t High current density OLED Temperature increase up to 70°C for Joule effect increase up to 70 C for 100 cd/m2

Thermal conductivity of organic thin films ?

3

Measurement of thin film thermal properties Context PTR 3 ω Comparison Conclusion Monitoring Organic thin films thermal conductivity measurement methods e<100nm Transient methods

• Transient plane source

Transient methods Not very accurate

• Laser Flash methods
• Photothermal radiometry (PTR)

Too much temperature increase Thi t d

• 3 omega (3)

This study 4

Context PTR 3 ω Comparison Conclusion

Outline Outline

• Radiothermal photometry (PTR)
• 3 omega (3)

g ( )

• Comparison

Conclusion & Perspectives

• Conclusion & Perspectives

5

Photothermal radiometry (PTR) Presentation Context PTR 3 ω Comparison Conclusion Monitoring Use of microlens beam-shaper for uniform sample irradiation

• 1-D model down to 0 1 Hz
• 1 D model down to 0.1 Hz
• Homogeneous phase up to 0.1 MHz

Observation scale µ, Diffusion length: mm to µm Use of gold layer to increase absorption 6

PTR Measurements Context PTR 3 ω Comparison Conclusion Monitoring

1.0 185 nm

• 20

Thi k 0.8 400 nm 600 nm 785 nm s

• 1/2)

Thi k

• 40
• 30

e (°) Thickness 0.4 0.6 T.F

½ (K.

Thickness

• 50
• 40

185 nm 400 nm 600 nm Phase 10 10

1

10

2

10

3

10

4

10

5

0.2 Frequency (Hz) 10 10

1

10

2

10

3

10

4

10

5

• 60

785 nm Frequency (Hz)

Gold layer thickness: 100 nm (PVD) Alq3 layer thickness: 185 nm to 785 nm (Thermal evaporation) Alq3 layer thickness: 185 nm to 785 nm (Thermal evaporation) Shift to low frequency with thickness Thermal model Thermal properties 7

PTR Analysis Context PTR 3 ω Comparison Conclusion

1.0 1.2

Theorical curve: Alq3 185 nm Experimental points: Alq3 185 nm Theorical curve: Alq3 600 nm E i l i Al 3 600

1-D model 3 layers

0.6 0.8

Experimental points: Alq3 600 nm

F

½ (K.s

• 1/2)

3 layers Thermal interfacial resistance included in the thermal conductivity measurement

10 10

1

10

2

10

3

10

4

10

5

0.2 0.4 T.F

h

Q (W.m-2)

10 10 10 10 10 10 Frequency (Hz)

• 20

z

Gold Alq3 Quartz

• Agreement between measured and computed values
• 40
• 30

se (°)

Quartz

• 3 layers model, limit of detection: 185 nm
• Alq3 thermal conductivity:
• Alq3 ρCp: 1.5-3.5 106 J.m-3.K-1
• 50

Theorical curve: Alq3 185 nm Experimental points: Alq3 185 nm Theorical curve: Alq3 600 nm

Phas

0.07-0.1 W.m-1.K-1

10 10

1

10

2

10

3

10

4

10

5

• 60

Experimental points: Alq3 600 nm

Frequency (Hz)

8

Context PTR 3 ω Comparison Conclusion Presentation of the 3 method Monitoring Principle: Thin metal strip used as a heater and a temperature sensor

Alq3 Gold 30m wide

          ) t 3 cos( T 1 ) t cos( T 1 ) t cos( ) T 1 ( I R ) t ( U           

p

) T 1 ( R R    

Alq3 Quartz

with

          ) t 3 cos( T 2 ) t cos( T 2 ) t cos( ) T 1 ( I R ) t ( U

ac ac dc

          

Thermal properties

) T 1 ( R R    

with

U(t) Lock-In Use of Wheatstone bridge (x103) + Lock-in amplifier (x105 ) AC lt + Lock-in amplifier (x10 ) Diffusion length: µm to mm Thi fil thi k 10 t 1 voltage Thin film thickness: 10 nm to 1 µm 9

Thin metal strip characteristics Context PTR 3 ω Comparison Conclusion

60 37.5 µm

Gold thin film

20 40 Height (nm)

Sputtering : length: 1.4 mm width: 30-40 µm thickness: 30 nm

800 820 840 860 880 900 Position (µm)

1.08

Systematic control using:

• profilometer
• optical microscope

1.04 1.06

R0

α=1.67 mK-1 Gold thin film temperature coefficient ? DC source and small variation

1 00 1.02

R/R

)) ( 1 ( T T R R    

5 10 15 20 25 30 35 40 1.00

T-T0 (K)

10

3 measurements and analysis Context PTR 3 ω Comparison Conclusion 6 2 < f/Hz < 5000 4 Integral calculus method (Cahill 1990*) : 300 K Alq3≈200 nm

In phase

2 TAC (K)

f f s AC

bK Pd dk Ds i k kb kb P T 2 ) / 2 ( ) ( ) ( sin ) (

2 2 2

2 1

   





  



Substrat Thin film

Out of phase

10

• 1

10 10

1

10

2

10

3

10

4

• 2

Frequency (Hz)  Agreement between experimental and theoretical curves

*D.G. Cahill,, Rev. Sci. Instrum. 61 (1990) 802–808.

11

1.6

1)

1500

Context PTR 3 ω Comparison Conclusion 3 results

1.2 1.4 ty (W.K

• 1.m
• 1

1000 1500 K

• 1)

Substrate Substrate

0.6 0.8 1.0 al conductivit 500 Cp (J.kg

• 1.

50 100 150 200 250 300 350 400 0.4 0.6 Therma Temperature (K) 100 200 300 400 Temperature (K) 0.07 .m

• 1)

Thin film Thermal properties of Quartz: Ks=1.43 W.m-1.K-1, Cps=848 J.kg-1. K-1 at 300K

0.06 tivity (W.K

• 1.

Alq3 thin Film at 300 K: K 0 067 W

1 K 1

0.05 rmal conduc

Kf=0.067 W.m-1.K-1

50 100 150 200 250 300 350 400 0.04 Ther Temperature (K)

12

Context PTR 3 ω Comparison Conclusion PTR vs 3

0.12

1.K

• 1)

Alq3 300K

0.08 0.10

ity (W.m

• 300K

0 04 0.06

PTR

conductiv

200 400 600 800 0.02 0.04

PTR 3

Thermal c T Thickness (nm)

Closeness of the agreement between PTR and 3 measurements g  Some literature results for thermal cond of Alq3:

• Pills (0.1 W.m-1.K-1)
• Thin films (One time sublimated: 0.5 W.m-1.K-1)

Thin films (One time sublimated: 0.5 W.m K ) Thermal conductivity decrease for reduced Alq3 thickness (for 25 < e < 600nm) 13

Context PTR 3 ω Comparison Conclusion C l i Monitoring

• Thermal conductivity measurement : Alq3 layer from 45 to 785 nm

at the same scale as in OLED Conclusion at the same scale as in OLED

• Thermal properties measurement performed by 2 techniques :
• photothermal radiometry (PTR)

3 omega (3)

• 3 omega (3)
• Closeness of the agreement between PTR and 3 measurements

Perspectives  Aging effect on Alq3 thermal properties  Thermal conductivity increase by doping y y p g  Temperature decrease during OLEDs operation (Active cooling: Peltier?) 14

Thanks for your attention

Aknowledgment : Région Pays de la Loire-Project PERLE2

3rd European Energy Conference , Budapest Oct 27‐30 2013