Modification by Jason Marmon, George Lisensky, and Wendy deProphetis
from Frank G. Gao and Allen J. Bard, "Solid-State Organic Light-Emitting
Diodes Based on Tris(2,2'-bipyridine)ruthenium(II) Complexes,"Journal
of the American Chemical Society, 122(30),
7426-7427 (2000) and Hannah
Sevian, Sean Muller, Hartmut Rudmann, and Michael F. Rubner, "Using Organic
Light-Emitting Electrochemical Thin-Film Devices to Teach Materials Science,"Journal of Chemical Education, 81(11),
1620 (2004).
A coordination complex between a transparent tin oxide electrode and an active metal electrode produces light when an external voltage is supplied.
Procedure
Wear eye protection
Chemical gloves recommended
Identify the conducting side of a tin oxide-coated piece of glass by
using a multimeter to measure resistance. The conducting side will have
a finite resistance of 20-30 ohms.
Use double-stick tape to attach indium-tin oxide glass with the conductive
side up to a 2500 rpm fan.
Use a cotton applicator to spread a layer of [Ru(bpy)3](BF4)2
polyvinylalcohol solution on the center of the glass. Surround with a
splatter shield and spin at 2500 rpm for 30-60 seconds. Repeat for a total
of 3-4 applications, trying to keep some uncoated regions at the edges.
Instead of using the preferred spin coating method in the previous step, use double-stick tape to attach indium-tin oxide glass with the conductive
side up to the benchtop. Use a cotton applicator to spread a very thin layer of [Ru(bpy)3](BF4)2
polyvinylalcohol solution on the glass. Evaporate using a heat gun or
hair drier. Repeat for a total of 3-4 applications, trying to keep some
uncoated regions at the edges.
Prepare a mask using a piece of duct tape on aluminum foil and punching a 2/16 inch hole.
Remove any remaining moisture in the film by heating for at least
a minute in a hair drier. The primary reason for failure of oLEDs to light
is insufficient drying of the polymer layer before adding the active metal layer.
Use a cotton swab to paint through the template with liquid gallium-indium
alloy to add an active metal electrode. (This eutectic mixture of 75.5%
gallium and 24.5% indium is a liquid above 16.5 degrees centigrade.)
Touch the positive lead of a 4.5-volt power supply to the tin-oxide
glass (not the [Ru(bpy)3](BF4)2
coating). Gently touch the negative lead to the gallium-indium.
In humid environments the lifetime is greatly shortened.
View from under the indium-tin oxide glass (left) or view in the dark (right).
Materials
Stock Solutions for multiple preparations.
Place approximately 0.30 g PVA (polyvinyl alcohol, Aldrich, 36,316-2, Average MW 124,000-186,000) and 10 mL of water
in a 30-mL beaker. Dissolve the PVA by placing plastic wrap loosely over
the beaker and heating in a microwave repeatedly for 15 second increments
until dissolved. Do not allow the solution to boil.
Dissolve approximately 0.035 g [Ru(bpy)3](BF4)2 (Synthesis)
in 3 mL of polyvinylalcohol solution.
GaIn Eutectic, Aldrich, 49542-5
Equipment
Conductive Glass (1" x 1" x 2.3mm TEC 15 glass), Hartford Glass Co,
735 E Water Street, Hartford City, IN 47348 Phone: 765-348-1282
Ohmeter
2500 rpm fan and power supply, Radio Shack 273-243B
12VDC Cooling Fan, 273-1662 Universal Power Adapter
