Online proceedings - EDA Publishing Association

Yamasaki et al., 2000 [11], consisting hexagonally
closed-packed arrays of silica microspheres with the
diameter of 550 nm, were incorporated into OLED with a
conventional two-layer structure to enhance the external
quantum efficiency. Tsutsui et al., 2000 [12], incorporated
closed-packed arrays of silica microspheres with the
diameter of 550 nm into organic light-emitting devices,
increase the external quantum efficiency of 80%. Hobson et
al. 2002 [13], apply wavy component surface cause surface
plasmon resonance let light deliver out of the component.
From these references, the external quantum efficiency of
OLED could be increased by disturbing optical waveguide
such as adding high packing ratio array lens brightness
enhancement film. In this work, a new method of improve
the external quantum efficiency of OLED by adding Ag
particle into the silicon oil layer were applied.
11-13
May 2011, Aix-en-Provence, France
electron injection layer (EIL) Alq3 (700 Å), electron
transport layer (ETL) LiF (12 Å), and Cathode Al (1500 Å).
Pack under nitrogen atmosphere to finish green light OLED
(Fig 3).
II. EXPERIEMNTS
The optical lithography of like-LIGA technique is used
to manufacture the micro-scale array lens brightness
enhancement film, combined with Ag particle adding silicon
oil, form a low optical waveguide structure. The processes
include optical lithography, the fabrication of OLED with
Ag particle adding silicon oil, micro-structure measurement
and optical brightness measurement.
2.1 Device fabrication
The upper and lower rows of apertures were arranged
equidistantly. Round patterns laid out in an ortho-triangle on
the PET-based mask, to provide the cylinder of photo
resistor for further proces. The pore size is 30μm, gap is
50μm (Fig 1). The experiment parameter shows in Table 1.
The base plate was washed by acetone for cleaning the oil
and dust on the surface, further washed by DI water then dry
by nitrogen gas. The optical lithography processes include
photo resistor coating, soft bake, exposure, and hot process.
The AZ4620 photo resistor is spread on base plate through
two stage spin coating. The purpose of first stage (300 rpm,
10 sec) coating is spraying the photo resistor on the base
plate. The thickness of photo resistor is controlled by the
second stage spin coating (1500 rpm, 25 sec). After soft bake
(90 ℃ , 3min) and exposure (15sec), the base plate was put
into AZ 300MIF developer for several minutes, then the
cylinder structure was formed on the plate surface. In hot
process (160 ℃ , 10min), the kinetic energy of photo resistor
molecular increased due to the temperature raise, with the
effect of surface tension, the photo resistor will form the
shape similar to spherical surface.
Mixing PDMS and hardener at the ratio 10:1 then spray it
on the plate surface, hard baking at 60C for 4 hr. Detach
PDMS from the base plate, then get PDMS plate with indent
array lens structure on it. The UV-curing PMMA was coated
between PDMS plate and PET plate. Exposure this
combined plate under UV light for curing the PMMA.
Detach PDMS mold from this combined plate, attach this
plate on the OLED device surface by the Ag particle adding
silicon oil. The concentration of Ag particle is 0.5%, the
particle size is up to 0.5 μm. The fabrication of OLED is first
etching desired figure on ITO glass plate, then evaporation
coating in order of hole transport layer (HTL) NPb (500 Å),
Fig. 1 Design pattern layout on the PET mask. (unit:μm).
Table 1 Experimental parameters in lithography process.
Base plate clean H 2 SO 4 :H 2 O 2 =3:1 wash
Acetone:60 min
DI Water wash,N 2 dry
120℃bake 20 min dry
Spin coating Spread : 500 rpm 10 sec
Spin : 2000-800 rpm 30 sec
Soft bake 90℃ 3min
Hold 5 min
Exposure 350W, Near UV
600mJ/cm 2
Develop
3.5min
Hot process 160℃ , 30 min
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