Name: fabrication of white light-emitting electrochemical cells with stable emission from exciplexes
Uploaded: 2016-11-15T13:00:00
Description: Watch this Scientific Journal Video about Fabrication of White Light-emitting Electrochemical Cells with Stable Emission from Exciplexes at JoVE.com

This work was partially supported by a Grant-in-Aid for Scientific Research (No. 24225003). This work was supported financially by the JX Nippon Oil &#38; Energy Corporation.

1. Preparation of Active Layer Solutions
<ol>
	<li>Active layer solution for the amine doped PFD devices 
	NOTE: The PFD, 4,4&#39;,4&#39;&#39;-tris[2-naphthyl(phenyl)amino]triphenylamine (2-TNATA), 9,9-dimethyl-N,N&#39;-di(1-naphthyl)-N,N&#39;-diphenyl-9H-fluorene-2,7-diamine (DMFL-NPB), Poly(ethylene oxide) (PEO), were used as received. The potassium trifluoromethanesulfonate (K2CF3SO3) was dried under vacuum at 200 &#176;C for 1 hr prior to use....

<ol>
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The LEC has an active layer containing hydrophobic PFD and aromatic amines, and hydrophilic polyethylene oxide and KCF3SO3. Because these materials have very different solubilities, careful preparation of the spin coating solution is critical to avoid incomplete solvation. Each must be first dissolved separately and completely in solvents with sufficient solvating ability, then the solutions are mixed together to form a uniform mixture. Balancing the exciton and exciplex emissions is key to obtainin...

Research and development of polymer light-emitting electrochemical cells (PLECs) have expanded in recent years.1-15 PLECs are similar to organic light-emitting diodes (OLEDs) in that both are surface emitting organic devices and are expected to find their way into future lighting applications. OLEDs are already on the market, but the cost is still high, one reason being that OLEDs need a complicated device structure with multiple layers. In contrast, PLECs have a very simple device structure which consists of a single active layer (emitting layer) between a pair of electrodes. This means that PLECs are suited to mass production processes such as roll-to-roll printing and coating. 
A PLEC has an active layer consisting of a fluorescent &#960;-conjugated polymer (FCP). The FCP can be electrochemically doped with a polymer electrolyte (a mixture of an ion conducting polymer and a salt). The FCP is p-doped on the anode side and n-doped on the cathode side during operation, and generates excitons which emit light between the p- and n-doped regions. Therefore, the emission color reflects the exciton emission (=fluorescence) wavelength of the FCP.
Stable white light emission is important for lighting applications, and color mixing techniques which employ two or more emitters have been widely used to achieve this.10-14 Recently, we presented a different approach for obtaining stable white light emission, using an active layer which contains blue-fluorescent poly(9,9-di-n-dodecylfluorenyl-2,7-diyl) (PFD) and &#960;-conjugated aromatic amines15. This white light emission comes from exciplexes formed between PFD and amine molecules in excited states. Exciplex emission has a broader spectrum compared to the exciton emission from the PDF and/or amines, which gives it a color close to that of natural light. This translates to a higher color rendering index (CRI), which is preferable for lighting applications.
In this article, the authors describe the procedure used to fabricate the exciplex based LECs and show the stability of their white light emission.

<table border="0" cellpadding="0" cellspacing="0" width="734">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:332px;">Poly(9,9-di-n-dodecylfluorenyl-2,7-diyl) (PFD)</td>
			<td style="width:99px;">Aldrich</td>
			<td style="width:115px;">571660</td>
			<td style="width:189px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:332px;">4,4&#8217;,4&#8217;&#8217;-Tris[2-naphthyl(phenyl)amino]triphenylamine (2-TNATA)</td>
			<td style="width:99px;">Aldrich</td>
			<td style="width:115px;">768669</td>
			<td style="width:189px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:332px;">9,9-Dimethyl-N,N&#8217;-di(1-naphthyl)-N,N&#8217;-diphenyl-9H-fluorene-2,7-diamine (DMFL-NPB)</td>
			<td style="width:99px;">Aldrich</td>
			<td style="width:115px;"></td>
			<td style="width:189px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:332px;">Poly(ethylene oxide) (PEO)</td>
			<td style="width:99px;">Aldrich</td>
			<td style="width:115px;">182028</td>
			<td style="width:189px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:332px;">Potassium tirifluoromethansulfonate (KCF3SO3)</td>
			<td style="width:99px;">Aldrich</td>
			<td style="width:115px;">422843</td>
			<td style="width:189px;">dried under vacuum at 200 &#176;C for 2 hr prior to use</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:332px;">Chloroform</td>
			<td style="width:99px;">Kanto Chemical Co.</td>
			<td style="width:115px;">08097-25</td>
			<td style="width:189px;">dehydrated</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:332px;">Cyclohexanone</td>
			<td style="width:99px;">Kanto Chemical Co.</td>
			<td style="width:115px;">07555-00</td>
			<td style="width:189px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:332px;">SCAT 20-X (detergent)</td>
			<td style="width:99px;">Daiichi Kogyo Seiyaku</td>
			<td style="width:115px;"></td>
			<td style="width:189px;">diluted with water</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:332px;">Acetone</td>
			<td style="width:99px;">Kanto Chemical Co.</td>
			<td style="width:115px;">01866-25</td>
			<td style="width:189px;">Electronic grage</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:332px;">2-propanol</td>
			<td style="width:99px;">Kanto Chemical Co.</td>
			<td style="width:115px;">32439-75</td>
			<td style="width:189px;">Electronic grage</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:332px;">13mm GD/X Disposable Filter Device PVDF Filter Media, Polypropylene Housing</td>
			<td style="width:99px;">Whatman</td>
			<td style="width:115px;">6872-1304</td>
			<td style="width:189px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:332px;">UV/O3 Treating Unit</td>
			<td style="width:99px;">SEN Lights Co.&#160;</td>
			<td style="width:115px;">SSP16-110</td>
			<td style="width:189px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:332px;">Spectral Photo Detector</td>
			<td style="width:99px;">Otsuka Electronics</td>
			<td style="width:115px;">MCPD 9800</td>
			<td style="width:189px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:332px;">Voltage Current Source Monitor</td>
			<td style="width:99px;">&#160;ADCMT</td>
			<td style="width:115px;">6241A&#160;</td>
			<td style="width:189px;"></td>
		</tr>
		<tr height="168">
			<td height="168" style="height:168px;width:332px;">Evaporation Mask</td>
			<td style="width:99px;">&#160;Tokyo Process Service Co., Ltd.</td>
			<td style="width:115px;">NA</td>
			<td style="width:189px;">The evaporation mask was wet-etched to create openings for patterned deposition of aluminum. The size of the mask is 100 mm x 100 mm x 0.2 mm-thick.</td>
		</tr>
	</tbody>
</table>

fabrication of white light-emitting electrochemical cells with stable emission from exciplexes

The authors present an approach for fabricating stable white light emission from polymer light-emitting electrochemical cells (PLECs) having an active layer which consists of blue-fluorescent poly(9,9-di-n-dodecylfluorenyl-2,7-diyl) (PFD) and &#960;-conjugated triphenylamine molecules. This white light emission originates from exciplexes formed between PFD and amines in electronically excited states. A device containing PFD, 4,4&#39;,4&#39;&#39;-tris[2-naphthyl(phenyl)amino]triphenylamine (2-TNATA), Poly(ethylene oxide) and K2CF3SO3 showed white light emission with Commission internationale de l&#39;&#233;clairage (CIE) coordinates of (0.33, 0.43) and a Color Rendering Index (CRI) of Ra = 73 at an applied voltage of 3.5 V. Constant voltage measurements showed that the CIE coordinates of (0.27, 0.37), Ra of 67, and the emission color observed immediately after application of a voltage of 5 V were nearly unchanged and stable after 300 sec.

The electroluminescence (EL) spectra were used to calculate the CIE coordinates and CRI values (Figures 2, 4, 5). Photographic images of the emitting devices were collected to verify the whiteness of the emission (Figure 3).
The EL spectra of the amine doped PFD devices and the undoped PFD device are shown in Figure 2. The undoped PFD device showed blue emission that corresponds...

Watch this Scientific Journal Video about Fabrication of White Light-emitting Electrochemical Cells with Stable Emission from Exciplexes at JoVE.com

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

The authors present a method for fabricating stable white-light-emitting electrochemical cells utilizing emission from exciplexes formed between a blue-emitting fluorene polymer and aromatic amines.

The authors present an approach for fabricating stable white light emission from polymer light-emitting electrochemical cells (PLECs) having an active ...

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.

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