Name: well-aligned vertically oriented zno nanorod arrays and their application in inverted small molecule solar cells
Uploaded: 2018-04-25T12:30:00
Description: Watch this Scientific Journal Video about Well-aligned Vertically Oriented ZnO Nanorod Arrays and their Application in Inverted Small Molecule Solar Cells at JoVE.com

The authors would like to thank the National Science Council of China for the financial support of this research under Contract No. MOST 106-2221-E-239-035, and MOST 106-2119-M-033-00.

1. Growth of AZO Sputtered Seed Layer on ITO Substrate
<ol>
	<li>Stick 4 anti-corrosion tape pieces (0.3 x 1.5 cm) on one side of the indium tin oxide (ITO) substrate to form a square (1.5 x 1.5 cm). Put the ITO into hydrochloric acid for 15 min to etch the exposed area of ITO.</li>
	<li>Remove the tape and clean the sample using a sonicator; sonicate with deionized (DI) water, acetone, ethanol, and isopropanol in turn for 30 min each. Blow-dry the patterned ITO with a compressed nitrogen gun.</li>
	<li>Attach the clea...

<ol>
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Mater. 24 (38), 5267-5272 (2012).</li><li>Dou, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Systematic+Investigation+of+Benzodithiophene-+and+Diketopyrrolopyrrole-Based+Low-Bandgap+Polymers+Designed+for+Single+Junction+and+Tandem+Polymer+Solar+Cells.">Systematic Investigation of Benzodithiophene- and Diketopyrrolopyrrole-Based Low-Bandgap Polymers Designed for Single Junction and Tandem Polymer Solar Cells.</a> J. Am. Chem. Soc. 134 (24), 10071-10079 (2012).</li><li>Li, G., Zhu, R., Yang, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polymer+solar+cells.">Polymer solar cells.</a> Nat. 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Electron. 11 (11), 1828-1834 (2010).</li><li>Vandewal, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+the+origin+of+the+open-circuit+voltage+of+polymer-fullerene+solar+cells.">On the origin of the open-circuit voltage of polymer-fullerene solar cells.</a> Nat. Mater. 8, 904-909 (2009).</li><li>Sharma, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=X-ray+diffraction:+a+powerful+method+of+characterizing+nanomaterials.">X-ray diffraction: a powerful method of characterizing nanomaterials.</a> Recent Research in Science and Technology. 4 (8), 77-79 (2012).</li><li>Huggett, J. M., Shaw, H. 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F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influences+of+ZnO+sol-gel+thin+film+characteristics+on+ZnO+nanowire+arrays+prepared+at+low+temperature+using+all+solution-based+processing.">Influences of ZnO sol-gel thin film characteristics on ZnO nanowire arrays prepared at low temperature using all solution-based processing.</a> J. Appl. Phys. 103, 014304 (2008).</li><li>Leung, S. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light+Management+with+Nanostructures+for+Optoelectronic+Devices.">Light Management with Nanostructures for Optoelectronic Devices.</a> J. Phys. Chem. Lett. 5, 1479-1495 (2014).</li><li>Lee, C. 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By utilizing the NRs interlayer, both the Jsc and the FF of the devices can be improved. However, the surface roughness of NRs will also influence the subsequent processes. Thus, the orientation and the surface morphology of the NRs should be carefully manipulated. For a long time, the sol-gel processed ETL such as TiO2 and ZnO were commonly used in PSCs due to their simple procedures. However, the crystallization of sol-gel processed layers is generally of the amorphous type, and the surface morpho...

Organic photovoltaic (OPV) devices have recently undergone remarkable developments in the application of renewable energy sources. Such organic devices have many advantages, including solution-process compatibility, low cost, light weight, flexibility, etc.1,2,3,4,5 Up until now, polymer solar cells (PSCs) with a PCE of more than 10% have been developed by utilizing the conjugated polymers blended with PC71BM6. Compared to polymer-based PSCs, small molecule-based OPVs (SM-OPVs) have attracted more attention when it comes to fabricating OPVs due to their several distinct advantages, including well-defined chemical structures, facile synthesis and purification, and generally higher open-circuit voltages (Voc)7,8,9. At present, a 2-D structure conjugated small molecule SMPV1 (2,6-Bis[2,5-bis(3-octylrhodanine)-(3,3-dioctyl-2,2&#39;:5,2&#39;&#39;-terthiophene)]-4,8-bis((5-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b&#39;]dithiophene) with BDT-T (benzo[1,2-b:4,5-b&#39;]dithiophene) as the core unit and 3-octylrodanine as the electron-withdrawing end-group10 has been designed and used to blend with PC71BM for promising sustainable OPVs application. The PCE of conventional small molecule solar cells (SM-OPVs) based on SMPV1 blended with PC71BM has reached more than 8.0%10,11.
In the past, PSCs could be enhanced and optimized simply by adjusting the thickness of the active layer. However, unlike PSCs, SM-OPVs in general have a shorter diffusion length, which greatly limits the thickness of the active layer. Hence, to further increase the short current density (Jsc) of SM-OPVs, utilizing the nano-structure12 or NRs9 to improve optical absorption of SM-OPVs became necessary.
Among these methods, the anti-reflection NRs structure is generally effective for light harvesting of the active layer over a broad range of wavelengths; therefore, knowing how to grow well-aligned vertically oriented zinc oxide (ZnO) NRs is very critical. The surface roughness of the seed layer below the ZnO NRs layer has a great influence on the orientation of the NR arrays; therefore, in order to deposit well-oriented NRs, the crystallization of the seed layer needs to be precisely controlled9.
In this work, the AZO films are prepared by theRadio-Frequency (RF) sputtering technique. Compared with other techniques, RF sputtering is known to be an efficient technology that is transferable to industry for it is a reliable deposition technique, which allows the synthesis of high purity, uniform, smooth, and self-sustainable AZO thin films to grow over large area substrates. Utilizing the RF sputtering deposition enables the forming of high quality AZO films that exhibit high crystallization with reduced roughness of surface. Therefore, in the subsequent growth layer, the orientations of the NRs are highly aligned, even more so when compared to ZnO films prepared by the sol-gel method. Using this technique, the PCE of the inverted small molecule solar cells based on well-aligned vertically oriented ZnO NR arrays can reach 6.01%.

<table>
	<tbody>
		<tr>
			<td>AZO target</td>
			<td>Ultimate Materials Technology Co., Ltd.</td>
			<td>none</td>
			<td>AZO (2 wt% Al2O3 in ZnO) , 3&#8221;&#968;x 3mmt 
			+ 3mmt Cu B/P + Bonding</td>
		</tr>
		<tr>
			<td>SMPV1</td>
			<td>Luminescence Technology Corp.</td>
			<td>1651168-29-4</td>
			<td>2,6-Bis[2,5-bis(3-octylrhodanine)-(3,3-dioctyl-2,2&#39;:5,2&#39;&#39;-terthiophene)]-4,8-bis((5-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b&#39;]dithiophene</td>
		</tr>
		<tr>
			<td>RF sputtering system</td>
			<td>Kao Duen Technology Co., Ltd</td>
			<td>none</td>
			<td>http://www.kaoduen.com.tw/index.php?action=product</td>
		</tr>
		<tr>
			<td>Zinc Acetate Dihydrate</td>
			<td>J. T. Baker</td>
			<td>5970456</td>
			<td>4.39 g</td>
		</tr>
		<tr>
			<td>Monoethanolamine</td>
			<td>J. T. Baker</td>
			<td>141435</td>
			<td>1.22 g</td>
		</tr>
		<tr>
			<td>2-methoxyethanol</td>
			<td>Sigma-Aldrich</td>
			<td>109864</td>
			<td>40 mL</td>
		</tr>
		<tr>
			<td>Zinc Nitrate Hexahydrate</td>
			<td>J. T. Baker</td>
			<td>10196186</td>
			<td>1.49 g</td>
		</tr>
		<tr>
			<td>Hexamethylenetetramine</td>
			<td>Sigma-Aldrich</td>
			<td>100-97-0</td>
			<td>0.7 g</td>
		</tr>
		<tr>
			<td>Indium tin oxide (ITO)</td>
			<td>RiTdisplay</td>
			<td>none</td>
			<td>coated glass substrates (&#60;10 &#937; sq&#8211;1)</td>
		</tr>
		<tr>
			<td>AFM</td>
			<td>Veeco</td>
			<td>Innova SPM</td>
			<td></td>
		</tr>
		<tr>
			<td>SEM</td>
			<td>FEI</td>
			<td>Nova 200 NanoSEM</td>
			<td>operation voltage: 10 kV</td>
		</tr>
		<tr>
			<td>XRD</td>
			<td>Bruker</td>
			<td>D8 X-ray diffractometer</td>
			<td>2&#952; range: 10&#8211;90 &#176;; step size: 0.008 &#176;</td>
		</tr>
		<tr>
			<td>PL</td>
			<td>Horiba</td>
			<td>Jobin-Yvon HR800</td>
			<td>excitation source: 325 nm UV Laser 20 mW</td>
		</tr>
		<tr>
			<td>solar simulator</td>
			<td>Newport</td>
			<td>91192A</td>
			<td>AM 1.5G</td>
		</tr>
		<tr>
			<td>Precision Semiconductor Parameter Analyzer</td>
			<td>Keysight Technologies</td>
			<td>Agilent 4156C</td>
			<td>sweep from -1 to +1 V</td>
		</tr>
		<tr>
			<td>toluene</td>
			<td>Sigma-Aldrich</td>
			<td>108-88-3</td>
			<td>1 mL</td>
		</tr>
		<tr>
			<td>PC71BM</td>
			<td>Sigma-Aldrich</td>
			<td>609771-63-3</td>
			<td>11.25 mg</td>
		</tr>
		<tr>
			<td>Thermal evaporation system</td>
			<td>Kao Duen Technology Co., Ltd</td>
			<td>Kao Duen PVD System</td>
			<td>http://www.kaoduen.com.tw/index.php?action=product</td>
		</tr>
		<tr>
			<td>HCl</td>
			<td>Sigma-Aldrich</td>
			<td>7647-01-0</td>
			<td></td>
		</tr>
		<tr>
			<td>MoO3</td>
			<td>Alfa Aesar</td>
			<td>1313-27-5</td>
			<td>99.50%</td>
		</tr>
		<tr>
			<td>silver ingot</td>
			<td>ADMAT Inc.</td>
			<td>none</td>
			<td>100.00%</td>
		</tr>
		<tr>
			<td>Thin Film Deposition Controller</td>
			<td>INFICON</td>
			<td>XTC</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-corrosion tape (Polyimide Film)</td>
			<td>3M Taiwan Corporation</td>
			<td>none</td>
			<td>http://solutions.3m.com.tw/wps/portal/3M/zh_TW/InsulatingTape/home/product/Polyimide/</td>
		</tr>
		<tr>
			<td>spin-coater</td>
			<td>Chemat Technology, Inc</td>
			<td>KW-4A</td>
			<td>http://www.chemat.com/chematscientific/KW-4A.aspx</td>
		</tr>
	</tbody>
</table>

well-aligned vertically oriented zno nanorod arrays and their application in inverted small molecule solar cells

This manuscript describes how to design and fabricate efficient inverted solar cells, which are based on a two-dimensional conjugated small molecule (SMPV1) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), by utilizing ZnO nanorods (NRs) grown on a high quality Al-doped ZnO (AZO) seed layer. The inverted SMPV1:PC71BM solar cells with ZnO NRs that grew on both a sputtered and sol-gel processed AZO seed layer are fabricated. Compared with the AZO thin film prepared by the sol-gel method, the sputtered AZO thin film exhibits better crystallization and lower surface roughness, according to X-ray diffraction (XRD) and atomic force microscope (AFM) measurements. The orientation of the ZnO NRs grown on a sputtered AZO seed layer shows better vertical alignment, which is beneficial for the deposition of the subsequent active layer, forming better surface morphologies. Generally, the surface morphology of the active layer mainly dominates the fill factor (FF) of the devices. Consequently, the well-aligned ZnO NRs can be used to improve the carrier collection of the active layer and to increase the FF of the solar cells. Moreover, as an anti-reflection structure, it can also be utilized to enhance the light harvesting of the absorption layer, with the power conversion efficiency (PCE) of solar cells reaching 6.01%, higher than the sol-gel based solar cells with an efficiency of 4.74%.

The layered structure of the devices consisted of an ITO substrate/AZO (40 nm)/ZnO NRs layer, SMPV1:PC71BM (80 nm)/MoO3 (5 nm)/Ag (150 nm) as shown in Figure 1. In general, the AZO or ZnO seed layer is widely used to function as the electron transport layer (ETL) in PSCs devices. Apart from PSCs, SM-OPVs usually have a shorter active layer, limited by the shorter diffusion length8. Hence, to further improve the li...

Watch this Scientific Journal Video about Well-aligned Vertically Oriented ZnO Nanorod Arrays and their Application in Inverted Small Molecule Solar Cells at JoVE.com

Well-aligned Vertically Oriented ZnO Nanorod Arrays and their Application in Inverted Small Molecule Solar Cells

This manuscript describes how to design and fabricate efficient inverted SMPV1:PC71BM solar cells with ZnO nanorods (NRs) grown on a high quality Al-doped ZnO (AZO) seed layer. The well-aligned vertically oriented ZnO NRs exhibit high crystalline properties. The power conversion efficiency of solar cells can reach 6.01%.

This manuscript describes how to design and fabricate efficient inverted solar cells, which are based on a two-dimensional conjugated small molecule ...

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