Fabrication of White Light-emitting Electrochemical Cells with Stable Emission from Exciplexes

The overall goal of this procedure is to fabricate very simple polymer light-emitting electrochemical cells in the lab, and to obtain the sort of white emission that is required for lighting applications. This method can help solve the issues in the fabrication of organic electronic devices such as light-emitting electrochemical cells. The main advantage of this technique is that white emission, which is critical for light application, can be obtained by a very simple procedure.

Generally, chemists who are new to organic device fabrication will struggle, because the procedures are different from those of organic synthesis and other types of lab experiments. Once mastered, these techniques will allow you to fabricate your own devices for testing using materials you create. First, dissolve ten milligrams of PFD, and two point five milligrams of the desired aromatic amine in one milliliter of chloroform, for devices having a PFD to amine ratio of one to zero point two five.

Prepare an undoped PFD device by dissolving ten milligrams of PFD in one milliliter of chloroform. Stir each mixture for one hour at forty degrees celsius. Next, dissolve ten milligrams of polyethylene oxide, or PEO, in one milliliter of cyclohexanone, and stir the mixture for one hour at sixty degrees celsius.

Then, dissolve two point five milligrams of potassium triflate in one milliliter of cyclohexanone, and stir the mixture for one hour at sixty degrees celsius. Using micro-pipettes, add zero point seven eight milliliters of the PEO solution, and zero point one four seven milliliters of the potassium triflate solution to the PFD solution. Stir the mixed solution for four hours at forty degrees celsius.

Following this, filter the mixed solution using a membrane filter prior to spin coating. Ultrasonically clean patterned indium tin oxide glass substrates with diluted detergent, ionized water, acetone, and 2-propanol using a desktop ultrasonic bath. When finished, remove the solvent using a nitrogen blower.

Treat the substrates with UV Ozone for three minutes using a UV Ozone treating unit, according to the manufacturer's protocol. After placing the substrates in a glove box, set a cleaned substrate on the head of a spin coater. Dispense around one hundred microliters of the active layer solution using a micro-pipette.

Then, spin at eight-hundred RPM for sixty seconds. Increase the rate to one thousand RPM over three seconds, and spin at one thousand RPM for ten seconds. After drying the coated substrates in the glove box overnight, wipe off excess polymer to ensure a proper electrode connection and encapsulation.

Following this, place the substrates on an evaporation holder for deposition of aluminum. Load the holder in the evaporation chamber. Then, thermally deposit a one hundred nanometer layer of aluminum at an evaporation rate of zero point four nanometers per second to a stainless steel evaporation mask, which has three millimeter-wide openings for depositing the aluminum counter electrodes.

When deposition is complete, transfer the devices to a glove box under an inert atmosphere. Apply a bead of UV curable epoxy resin in the shape of a rectangle using a dispenser. Place a cover glass on the resin to encapsulate the device.

Now, cure the resin using UV radiation from a UV LED light source. To perform J-V-L measurements, use a spectral photo detector equipped with a DC voltage current source monitor. After connecting the terminals to the contacts of the device with alligator clips, place the device on the measurement stage.

Run the control software for data acquisition, and record the emissions spectra collected by the spectrometer through an optical fiber. The electroluminescent spectra were used to calculate the CIE coordinates and CRI values. Photographic images of the emitting devices were collected to verify the whiteness of the emission.

After watching this video, you should have a good understanding of how to fabricate polymer light-emitting electrochemical cells in your laboratory. Once mastered, these techniques should allow you to test your own materials, which could help to further your research.