This work was partially supported by JSPS KAKENHI Grant Number 25871029, the Nippon Sheet Glass Foundation for Materials Science and Engineering, and the Tochigi Industrial Promotion Center. The National Institute of Technology, Oyama College, also assisted with the publication costs of this article.

1. Preparation of Indium-tin-oxide (ITO) Glass for Solar Cell Fabrication
<ol>
	<li>Cut the ITO/glass substrate.
	<ol>
		<li>Using a glass cutter, cut the ITO/glass substrate (10 cm &#215; 10 cm) into pieces measuring approximately 2 cm &#215; 2 cm.</li>
	</ol>
	</li>
	<li>Chemically etch the ITO conductive layer.
	<ol>
		<li>Using a digital multimeter, check that the top of the ITO/glass piece has a conductive side.</li>
		<li>Place masking tape on both sides of the ITO/glass piece, leaving a central area of 2 mm &#21...

<ol>
	<li>Price, C. S., Stuart, C. A., Yang, L., Zhou, H., You, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorine+substituted+conjugated+polymer+of+medium+band+gap+yields+7%+efficiency+in+polymer-fullerene+solar+cells.">Fluorine substituted conjugated polymer of medium band gap yields 7% efficiency in polymer-fullerene solar cells.</a> J. Am. Chem. Soc. 133 (12), 4625-4631 (2011).</li><li>Liang, Y. Y., 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=For+the+bright+future-Bulk+heterojunction+polymer+solar+cells+with+power+conversion+efficiency+of+7.4%.">For the bright future-Bulk heterojunction polymer solar cells with power conversion efficiency of 7.4%.</a> Adv. Mater. 22, 135-138 (2010).</li><li>Chu, T. -. Y., 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=Bulk+heterojunction+solar+cells+using+thieno[3,4-c]pyrrole-4,6-dione+and+dithieno[3,2-b:2',3'-d]silole+copolymer+with+a+power+conversion+efficiency+of+7.3%.">Bulk heterojunction solar cells using thieno[3,4-c]pyrrole-4,6-dione and dithieno[3,2-b:2',3'-d]silole copolymer with a power conversion efficiency of 7.3%.</a> J. Am. Chem. Soc. 133 (12), 4250-4253 (2011).</li><li>Zhou, H., 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=Development+of+fluorinated+benzothiadiazole+as+a+structural+unit+for+a+polymer+solar+cell+of+7%+efficiency.">Development of fluorinated benzothiadiazole as a structural unit for a polymer solar cell of 7% efficiency.</a> Angew. Chem. Int. Ed. 50 (13), 2995-2998 (2011).</li><li>Janssen, J. A. 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Today. 14 (10), 462-470 (2011).</li><li>He, Z., Zhong, C., Su, S., Xu, M., Wu, H., Cao, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+power-conversion+efficiency+in+polymer+solar+cells+using+an+inverted+device+structure.">Enhanced power-conversion efficiency in polymer solar cells using an inverted device structure.</a> Nat. Photonics. 6, 591-595 (2012).</li><li>Baena, J. P. C., 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=Highly+efficient+planar+perovskite+solar+cells+through+band+alignment+engineering.">Highly efficient planar perovskite solar cells through band alignment engineering.</a> Energy Environ. Sci. 8, 2928-2934 (2015).</li><li>Shuttle, G. C., Hamilton, R., O'Regan, B. C., Nelson, J., Durrant, R. 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The authors declare that they have no competing financial interests.

In order to utilize the molecule&#39;s bulkiness in this method, it is important to know the conditions for film formation by spin coating. First, the p-type and n-type semiconductors must be able to be dissolved in the solvents. When some material remains, it will become the large core of the domains in the photoactive layer. The use of an adequate commercial filter for individual solvents is recommended to remove the remaining material. Next, the precursor solution in which the molecules dissolve must be uniformly and ...

Organic photovoltaic devices are considered promising renewable energy sources due to their low manufacturing cost and light weight1-7. Because of these advantages, a large number of scientists have been immersed in this promising area. In the past decade, dye-sensitized, organic thin-film, and perovskite-sensitized solar cells have achieved significant progress in power conversion efficiency in this area8.
Specifically, organic thin-film solar cells and BHJ organic thin-film solar-cell technology are efficient and cost-effective solutions for the utilization of solar energy. Furthermore, the energy conversion efficiency has reached over 10% with the use of low-band-gap polymers as the electron donor and fullerene derivatives as the electron acceptor (Phenyl-C61-Butyric-Acid-Methyl Ester: [60]PCBM or Phenyl-C71-Butyric-Acid-Methyl Ester: [70]PCBM)9-11. Moreover, some researchers have already reported the importance of the BHJ structure in the photoactive layer, which is constructed with low-band-gap polymers and fullerene derivatives to obtain a high overall efficiency. However, fullerene derivatives are air-sensitive. Therefore, an air-stable electron-accepting material is required as an alternative. A few reports previously suggested new types of organic photovoltaic cells that used n-type semiconducting polymers or metal oxides as electron acceptors. These reports supported the development of air-stable, fullerene-free, organic thin-film solar cells12-15.
However, in contrast to fullerene systems or n-type semiconducting polymer systems, obtaining a satisfactory performance of the BHJ structure in the photoactive layer, which has charge separation and charge transfer abilities, is difficult in metal oxide systems16-17. Furthermore, fullerene derivatives and n-type semiconducting polymers have high solubility in many solvents. Therefore, it is easy to control the morphology of the photoactive layer by selecting an ink solution as the solvent, which is the precursor of the photoactive layer18-20. In contrast, in the case of metal alkoxide systems used in combination with an electron-donating polymer, both semiconductors are insoluble in almost all solvents. This is because metal alkoxides do not have a high solubility in the solvent. Therefore, the selectivity of solvents for morphology control is extremely low.
In this article, we report a method for controlling the morphology of the photoactive layer by using molecular bulkiness to fabricate printable and highly air-stable BHJ solar cells. We describe the importance of morphology control for the progress of fullerene-free BHJ solar cells.

<table border="0" cellpadding="0" cellspacing="0" width="625">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ti(IV) isopropoxide, 97%</td>
			<td style="width:103px;">Sigma Aldrich</td>
			<td style="width:119px;">205273</td>
			<td style="width:187px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ti(IV) ethoxide</td>
			<td style="width:103px;">Sigma Aldrich</td>
			<td style="width:119px;">244759</td>
			<td>Technical grade</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ti(IV) butoxide, 97%</td>
			<td style="width:103px;">Sigma Aldrich</td>
			<td style="width:119px;">244112</td>
			<td>Reagent grade</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ti(IV) butoxide polymer</td>
			<td style="width:103px;">Sigma Aldrich</td>
			<td style="width:119px;">510718</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Poly[2,7-(9,9-dioctylfluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PFO-DBT)</td>
			<td style="width:103px;">Sigma Aldrich</td>
			<td style="width:119px;">754013</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">[6,6]-phenyl-C61 butyric acid methyl ester ([60]PCBM) 99.5%</td>
			<td style="width:103px;">Sigma Aldrich</td>
			<td style="width:119px;">684449</td>
			<td>Research grade</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS)</td>
			<td style="width:103px;">Heraeus</td>
			<td style="width:119px;">Clevios S V3</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">1N Hydrochloric acid</td>
			<td style="width:103px;">Wako</td>
			<td style="width:119px;">083-01095</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Chlorobenzene 99.0%</td>
			<td style="width:103px;">Wako</td>
			<td style="width:119px;">032-07986</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Acetone 99.5%</td>
			<td style="width:103px;">Wako</td>
			<td style="width:119px;">016-00346</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Indium-tin oxide (ITO)-coated glass substrate</td>
			<td style="width:103px;">Geomatec</td>
			<td style="width:119px;">0002</td>
			<td>100&#215;100&#215;1.1t (mm)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Glass substrate</td>
			<td style="width:103px;">Matsunami Glass</td>
			<td style="width:119px;">S7213</td>
			<td>76&#215;26&#215;1.2t (mm)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Cotton tail&#160;</td>
			<td style="width:103px;">As one</td>
			<td style="width:119px;">1-8584-16</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Epoxy resin</td>
			<td style="width:103px;">Nichiban</td>
			<td style="width:119px;">AR-R30</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Plastic spatula</td>
			<td style="width:103px;">As one</td>
			<td style="width:119px;">2-3956-02</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ultrasonic cleaner</td>
			<td style="width:103px;">As one</td>
			<td style="width:119px;">AS482</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Magnetic hot&#160; stirrer</td>
			<td style="width:103px;">As one</td>
			<td style="width:119px;">RHS-1DN</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ceramic hotplate</td>
			<td style="width:103px;">As one</td>
			<td style="width:119px;">CHP-17DN</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Spin coater</td>
			<td style="width:103px;">Kyowariken</td>
			<td style="width:119px;">K-359 S1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Vacuum pump</td>
			<td style="width:103px;">ULVAC</td>
			<td style="width:119px;">DA-30S</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:216px;">UV-O3 cleaner</td>
			<td style="width:103px;">Filgen</td>
			<td style="width:119px;">UV253E</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Screen printer</td>
			<td style="width:103px;">Mitani Electronics</td>
			<td style="width:119px;">MEC-2400</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Ultrasonic Soldering system</td>
			<td style="width:103px;">Kuroda Techno</td>
			<td style="width:119px;">SUNBONDER USM-5</td>
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			<td height="63" style="height:63px;width:216px;">Direct-current voltage and current source/monitor integrated system</td>
			<td style="width:103px;">San-Ei Electric</td>
			<td style="width:119px;">XES-40S1</td>
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			<td height="21" style="height:21px;width:216px;">Scanning electron microscope</td>
			<td style="width:103px;">JEOL Ltd.</td>
			<td style="width:119px;">JSM-7800</td>
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</table>

morphology control for fully printable organic&#8211;inorganic bulk-heterojunction solar cells based on a ti-alkoxide and semiconducting polymer

The photoactive layer of a typical organic thin-film bulk-heterojunction (BHJ) solar cell commonly uses fullerene derivatives as the electron-accepting material. However, fullerene derivatives are air-sensitive; therefore, air-stable material is needed as an alternative. In the present study, we propose and describe the properties of Ti-alkoxide as an alternative electron-accepting material to fullerene derivatives to create highly air-stable BHJ solar cells. It is well-known that controlling the morphology in the photoactive layer, which is constructed with fullerene derivatives as the electron acceptor, is important for obtaining a high overall efficiency through the solvent method. The conventional solvent method is useful for high-solubility materials, such as fullerene derivatives. However, for Ti-alkoxides, the conventional solvent method is insufficient, because they only dissolve in specific solvents. Here, we demonstrate a new approach to morphology control that uses the molecular bulkiness of Ti-alkoxides without the conventional solvent method. That is, this method is one approach to obtain highly efficient, air-stable, organic-inorganic bulk-heterojunction solar cells.

We have presented a protocol for fabricating fully printable organic-inorganic BHJ solar cells, as well as a method for controlling the phase-separation structure. The solar-cell performance has been extensively investigated27-31 when Ti(IV) isopropoxide and ethoxide were used as electron-accepting materials (Figure 1). These solar cells exhibited a short-circuit current density (Jsc) that is approximately eight times higher than that of devices using the &#34;...

Watch this Scientific Journal Video about Morphology Control for Fully Printable Organicâ€“Inorganic Bulk-heterojunction Solar Cells Based on a Ti-alkoxide and Semiconducting Polymer at JoVE.com

Morphology Control for Fully Printable Organic&amp;#8211;Inorganic Bulk-heterojunction Solar Cells Based on a Ti-alkoxide and Semiconducting Polymer

A method for fully printable, fullerene-free, highly air-stable, bulk-heterojunction solar cells based on Ti alkoxides as the electron acceptor and the electron-donating polymer fabrication is described here. Moreover, a method for controlling the morphology of the photoactive layer through the molecular bulkiness of the Ti-alkoxide units is reported.

Morphology Control for Fully Printable Organic&#8211;Inorganic Bulk-heterojunction Solar Cells Based on a Ti-alkoxide and Semiconducting Polymer

The photoactive layer of a typical organic thin-film bulk-heterojunction (BHJ) solar cell commonly uses fullerene derivatives as the electron-accepting ...

The overall goal of this experiemnt is to fabricate fully-printable, fullerene-free bulk-heterojunction solar cells using bulky titanium alkoxides as morphology-controlling electron acceptors. This method can help answer key questions in the bulk heterojunction solar cell field about controlling the phase-separation structure of the photoactive layer of organic-inorganic hybrid bulk heterojunction solar cells. The main advantage of this technique is that it controls the phase-separation structure by hindering self-organization with bulky molecules without the solubility limitations of the conventional solvent method.The implications of this technique extend to obtaining higher overall solar cell efficiency because charged separations and charged transfer occur always in the active layer. So, this method can provide insight into the PFO-DVT electron donor system. It can also be operated with semiconducting polymers such as P3HT or PTV7.To begin the procedure, using a glass cutter, cut a 1.1-millimeter-thick ITO glass substrate into two-centimeter by two-centimeter squares. Identify the conductive side of each square with a digital multimeter. Cover the conductive side of each square with two strips of masking tape, leaving a two-millimeter by two-centimeter area exposed in the center.Place a few drops of one-molar hydrochloric acid onto the exposed, conductive area of each square. Allow the squares to sit for three minutes to etch a stripe in the conductive layer. Then, wipe off the hydrochloric acid with a cotton swap, and remove the masking tape.Place the squares in a glass container, and fill the container with deionized water. Place the container in an ultrasonic cleaner water bath. Run the ultrasonic cleaner at 42 kilohertz for 15 minutes.Then, clean the squares in acetone and isopropanol for 15 minutes each. Dry the squares under a stream of dry air. Then, clean the dry squares in an ultraviolet ozone cleaner for 30 minutes.To prepare the precursor solutions, dissolve 0.5 milligrams of PFO-DBT and 1.0 milligrams of the chosen titanium alkoxide in one milliliter of chlorobenzene. Wrap the vial in aluminum foil to exclude light. Heat the precursor mixture to 70 degrees Celsius while stirring at 700 RPM.Stir the mixture at that temperature for about 20 minutes. Once the solution appears clear, allow it to cool to room temperature. Dissolve 0.5 milligrams of PFO-DBT and 1.0 milligrams of 60-PCBM in one milliliter of chlorobenzene as a reference standard.Heat, stir, and cool the reference standard under the same conditions as the precursors. To prepare for a spin coating, pre-heat the precursor or reference solution on a hot plate at 70 degrees Celsius while stirring at 700 RPM for 10 minutes. Heat a square of etched ITO glass substrate on a ceramic hot plate at 70 degrees for five minutes.Then, place the warmed ITO glass square on the center of the spin coater vacuum stage. Reheat this square to 70 degrees with a heat gun, and then turn on the vacuum pump to fix the square in place. Draw 0.5 milliliters of warm precursor or reference solution into a one milliliter syringe, and immediately place the solution on the square.Then, run the spin coater at 2, 000 to 6, 000 RPM for 60 seconds in the air to create a 50-nanometer-thick film. Allow the surface to dry for 10 minutes at room temperature in the absence of light. Then, use a cotton swab, wetted with chlorobenzene, to remove excess photoactive material.Dry the surface again under the same conditions. To analyze the phase-separation structure, stop the preparation here, and use an optical or scanning electron microscope to obtain images of the photoactive layer. To print an organic electrode on a photoactive-material-coated ITO glass square, use a screen printer with a 50-micrometer-thick metal mask to print a five-millimeter by 20-millimeter rectangle of PDOT-PSS on the surface of the square.Allow the electrode to dry for 30 minutes in air at room temperature in the absence of light. Then, cut out a 1.5-centimeter by 2.5-centimeter piece of 1.2-millimeter-thick glass substrate with a diamond cutter. Spread epoxy resin on the glass piece with a plastic spatula.Place the glass epoxy-side down on the sample, leaving one side of the sample surface exposed. Clean the supporting electrodes with acetone and a cotton swab. Use a ultrasonic soldering iron to solder the supporting electrodes onto the remaining exposed surface of the square.Measure the current voltage characteristics of the cell with a solar simulator. Repeat this procedure for each titanium alkoxide to be tested and for PFO-DBT as a reference. Organic-inorganic bulk heterojunction solar cells were fabricated using four different titanium alkoxides as electron acceptors.The current voltage characteristics were significantly affected by the alkoxide properties, which was attributed to differences in the phase-separation structure of the photoactive layer. The short-circuit current densities of the cells using titanium four isopropoxide, ethoxide, and butoxide were much higher than that of the cell using a butoxide polymer. Scanning electron microscopy of the photoactive layers showed acceptable phase-separation structures for the titanium four ethoxide and isopropoxide cells.The titanium four butoxide cell showed somewhat worse phase separation, which was attributed to the bulkiness of the butoxide. The even-greater bulk of the titanium four butoxide polymer was prohibitive to optimal phase separation, resulting in poor charge generation in the photoactive layer. After each development, this technique paved the way for researchers in the field of organic-inorganic hybrid solar cells to explore the combinations of various materials for highly-efficient photoactive layers.

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9.0K ビュー.  National Institute of Technology, Oyama College. The overall goal of this experiemnt is to fabricate fully-printable, fullerene-free bulk-heterojunction solar cells using bulky titanium alkoxides as morphology-controlling electron acceptors. This method can help answer key questions in the bulk heterojunction solar cell field about controlling the phase-separation structure of the photoactive layer of organic-inorganic hybrid bulk heterojunction solar cells. The main advantage of this technique is that it controls the phase-separation struc...