Minlu Zhang
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Minlu Zhang. Outline. Small molecular OLEDs (OLED) Polymer OLEDs (PLED) Applications Challenges. Single layer device. Cathode. P-n junction device. Organic Layer. Multiple layers device. Anode. Cathode. Cathode. Substrate. Electron transport layer. Electron Injection layer.

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Minlu Zhang

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Minlu Zhang


Outline

  • Small molecular OLEDs (OLED)

  • Polymer OLEDs (PLED)

  • Applications

  • Challenges


Single layer device

Cathode

P-n junction device

Organic Layer

Multiple layers device

Anode

Cathode

Cathode

Substrate

Electron transport layer

Electron Injection layer

Hole transport layer

Electron transport layer

Anode

Emissive layer

Substrate

Hole transport layer

Hole Injection layer

Anode

Substrate

Small molecular OLEDs — Structure


Cathode

Electron Injection layer

Electron transport layer

Emissive layer

Transparent

substrate

ITO

HIL

HTL

EML

e-

ETL

EIL

Cathode

Hole transport layer

e-

e-

Hole Injection layer

Anode

Substrate

h+

h+

h+

Small molecular OLEDs — Device operation principle

  • Electrons injected from cathode

  • Holes injected from anode

  • Transport and radiative recombination of electron hole pairs at emissive layer

LUMO — Ec

Light

HOMO — Ev


Small molecular OLEDs — Materials

EIL, ETL: n-type materials

Alq3, PBD

PBD

Alq3

HIL, HTL: p-type materials

NPB, TPD

NPB

TPB

EML:

Fluorescent dye

DCM2

Phosphorescent dye

PtOEP, Ir(ppy)3

DCM2


Small molecular OLEDs — Electrodes

Anode:

Indium-tin-oxide (ITO): 4.5-5.1 eV

Au: 5.1 eV

Pt: 5.7 eV

Cathode:

Ca: 2.9 eV

Mg: 3.7 eV

Al: 4.3 eV

Ag: 4.3 eV

Mg : Al alloys

Ca : Al Alloys


Substrate

Vacuum

Cathode

Small molecules

Electron transport layer

Hole transport layer

Anode

Substrate

Heater

Small molecular OLEDs — Device preparation

Thermal vacuum evaporation

Growth:

~10-5-10-7 Torr

Room temperature

~20 Å- 2000 Å


Cathode

Cathode

Emissive polymer

Emissive polymer

Anode

Conducting polymer

Substrate

Anode

Substrate

Polymer OLEDs— Structure and Operation

http://www.ewh.ieee.org/soc/cpmt/presentations/cpmt0401a.pdf


Polymer OLEDs— Materials

Conducting polymers:

PANI:PSS

PDOT:PSS

PANI

PSS

PDOT

Emissive polymers:

R-PPV

PFO


Spin coating

Polymer film

Substrate

Ink jet printing

Substrate

Polymer OLEDs— Fabrication

Spin coating

Ink jet printing

Screen printing

Web coating


Why Organic LED?

  • Vibrant colors

  • High contrast

  • Wide viewing angles from all directions

  • Low power consumption

  • Low operating voltages

  • Wide operating temperature range

  • A thin and lightweight form factor

  • Cost-effective manufacturability , etc


A full color, 13-inch diagonal small-molecular-weight OLED display with 2mm thickness.

Flexible internet display screen

S. R. Forrest in Nature428, 911 (2004)

Applications — Full color OLED display


Samsung large OLED displays

KODAK OLED displays

http://www.kodak.com/eknec/PageQuerier.jhtml?pq-path=1473/1481/1491&pq-locale=en_US

Applications — Full color OLED display


White OLEDs

From Universal Display Corporation

http://www.universaldisplay.com/white.htm

Applications — Solid state white lighting


Challenges

  • Lifetime

  • Red >10,000 hrs

  • Green >10,000 hrs

  • Blue ~1,000hrs ?

  • High efficiency ?

  • Pure color?


Thank You!


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