16-03-2012, 11:43 AM
OLED DISPLAY SYSTEMS
[attachment=18418]
Potentials of OLED
Suitable for thin, lightweight, printable
displays
Broad color range
Good contrast
High resolution(<5 μm pixel size)
Fast switching (1-10 μs)
Wide viewing angle
Low cost of materials
Energy level diagram of OLED
• Electrons injected from the cathode (Ca, Al, Ba, etc.)
• Holes injected from the anode (Indium/tin oxide, PANi, PEDOT)
• Transport and radiative recombination of electron hole
pairs at the emissive polymer
A threshold voltage
must be achieved to
overcome the barriers
to inject charges into
the organic materials
N2 molecules doped
during the evaporation
of Alq3 cause the
expansion of the traps
states below the
LUMO thus lowering
the injection barrier for
electrons
Inkjet printing
Advantage: high-resolution,
low cost, materials saving
selectively deposit many
layers in a display
simultaneously
Surface properties of the
substrate affect the
uniformity of the film
thickness
Problems: layer shift and
dimentional changes from
the PLED drying and
evaporation process
Challenges and shortcomings II
Brightness and Lifetime Requirements
State of art OLED brightness and lifetime: 100 nits and
40,000 hours (50% initial luminance)
High brightness level require the display driving
voltage levels to be increased which trades off
expected lifetime. For most OLED materials, the
relationship between driving voltage level and lifetime
is nearly linear.
Moisture sensitivity
Over time, moisture can react with the organic layers
and cause degradation and defects in an OLED
display
Sealing techniques
Inserting desiccants
[attachment=18418]
Potentials of OLED
Suitable for thin, lightweight, printable
displays
Broad color range
Good contrast
High resolution(<5 μm pixel size)
Fast switching (1-10 μs)
Wide viewing angle
Low cost of materials
Energy level diagram of OLED
• Electrons injected from the cathode (Ca, Al, Ba, etc.)
• Holes injected from the anode (Indium/tin oxide, PANi, PEDOT)
• Transport and radiative recombination of electron hole
pairs at the emissive polymer
A threshold voltage
must be achieved to
overcome the barriers
to inject charges into
the organic materials
N2 molecules doped
during the evaporation
of Alq3 cause the
expansion of the traps
states below the
LUMO thus lowering
the injection barrier for
electrons
Inkjet printing
Advantage: high-resolution,
low cost, materials saving
selectively deposit many
layers in a display
simultaneously
Surface properties of the
substrate affect the
uniformity of the film
thickness
Problems: layer shift and
dimentional changes from
the PLED drying and
evaporation process
Challenges and shortcomings II
Brightness and Lifetime Requirements
State of art OLED brightness and lifetime: 100 nits and
40,000 hours (50% initial luminance)
High brightness level require the display driving
voltage levels to be increased which trades off
expected lifetime. For most OLED materials, the
relationship between driving voltage level and lifetime
is nearly linear.
Moisture sensitivity
Over time, moisture can react with the organic layers
and cause degradation and defects in an OLED
display
Sealing techniques
Inserting desiccants
