Name: electrospinning of photocatalytic electrodes for dye-sensitized solar cells
Uploaded: 2017-06-28T13:00:00
Description: Watch this Scientific Journal Video about Electrospinning of Photocatalytic Electrodes for Dye-sensitized Solar Cells at JoVE.com

The authors have no acknowledgements.

1. Precursor Solution Preparation
NOTE: Please consult all relevant material safety data sheets (MSDS) before use. Several of the chemicals used in this procedure are harmful and/or toxic to humans. Nanomaterials may have additional hazards compared to their bulk counterpart. Please use the appropriate safety measures and personal protective equipment.
<ol>
	<li>Place 5 g of titanium(IV) n-butoxide, 1 g of polyvinylpyrrolidone (PVP), 1 mL of glacial acetic acid, and 10 mL of absolute ethanol...

<ol>
	<li>O'Regan, B., Gr&#228;tzel, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+low-cost,+high-efficiency+solar+cell+based+on+dye-sensitized+colloidal+TiO2+films.">A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films.</a> Nature. 353 (6346), 737-740 (1991).</li><li>Lee, C. H., Chiu, W. H., Lee, K. M., Hsieh, W. F., Wu, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+performance+of+flexible+dye-sensitized+solar+cells+by+introducing+an+interfacial+layer+on+Ti+substrates.">Improved performance of flexible dye-sensitized solar cells by introducing an interfacial layer on Ti substrates.</a> J Mat Chem. 21 (13), 5114-5119 (2011).</li><li>Burschka, J., Pellet, N., 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=Sequential+deposition+as+a+route+to+high-performance+perovskite-sensitized+solar+cells.">Sequential deposition as a route to high-performance perovskite-sensitized solar cells.</a> Nature. 499 (7458), 316-319 (2013).</li><li>Ohsaki, Y., Masaki, N., 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=Dye-sensitized+TiO2+nanotube+solar+cells:+fabrication+and+electronic+characterization.">Dye-sensitized TiO2 nanotube solar cells: fabrication and electronic characterization.</a> Phys Chem Chem Phys. 7 (24), 4157-4163 (2005).</li><li>Mor, G. K., Shankar, K., Paulose, M., Varghese, O. K., Grimes, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+Photocleavage+of+Water+Using+Titania+Nanotube+Arrays.">Enhanced Photocleavage of Water Using Titania Nanotube Arrays.</a> Nano Letters. 5 (1), 191-195 (2005).</li><li>Feng, X., Shankar, K., Varghese, O. K., Paulose, M., Latempa, T. J., Grimes, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vertically+Aligned+Single+Crystal+TiO2+Nanowire+Arrays+Grown+Directly+on+Transparent+Conducting+Oxide+Coated+Glass:+Synthesis+Details+and+Applications.">Vertically Aligned Single Crystal TiO2 Nanowire Arrays Grown Directly on Transparent Conducting Oxide Coated Glass: Synthesis Details and Applications.</a> Nano Letters. 8 (11), 3781-3786 (2008).</li><li>Roy, P., Berger, S., Schmuki, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TiO2+Nanotubes:+Synthesis+and+Applications.">TiO2 Nanotubes: Synthesis and Applications.</a> Angewandte Chemie International Edition. 50 (13), 2904-2939 (2011).</li><li>Macdonald, T. J., Xu, J., 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=NiO+Nanofibers+as+a+Candidate+for+a+Nanophotocathode.">NiO Nanofibers as a Candidate for a Nanophotocathode.</a> Nanomaterials. 4 (2), 256-266 (2014).</li><li>Chuangchote, S., Sagawa, T., Yoshikawa, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+dye-sensitized+solar+cells+using+electrospun+TiO2+nanofibers+as+a+light+harvesting+layer.">Efficient dye-sensitized solar cells using electrospun TiO2 nanofibers as a light harvesting layer.</a> Appl Phys Lett. 93 (3), 033310 (2008).</li><li>Li, D., Xia, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospinning+of+Nanofibers:+Reinventing+the+Wheel?.">Electrospinning of Nanofibers: Reinventing the Wheel?.</a> Adv Mat. 16 (14), 1151-1170 (2004).</li><li>Li, W. J., Laurencin, C. T., Caterson, E. J., Tuan, R. S., Ko, F. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospun+nanofibrous+structure:+A+novel+scaffold+for+tissue+engineering.">Electrospun nanofibrous structure: A novel scaffold for tissue engineering.</a> J Biomed Mat Res. 60 (4), 613-621 (2002).</li><li>Jia, H., Zhu, G., Vugrinovich, B., Kataphinan, W., Reneker, D. H., Wang, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enzyme-Carrying+Polymeric+Nanofibers+Prepared+via+Electrospinning+for+Use+as+Unique+Biocatalysts.">Enzyme-Carrying Polymeric Nanofibers Prepared via Electrospinning for Use as Unique Biocatalysts.</a> Biotechnol Prog. 18 (5), 1027-1032 (2002).</li><li>Mai, L., Xu, 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=Electrospun+Ultralong+Hierarchical+Vanadium+Oxide+Nanowires+with+High+Performance+for+Lithium+Ion+Batteries.">Electrospun Ultralong Hierarchical Vanadium Oxide Nanowires with High Performance for Lithium Ion Batteries.</a> Nano Letters. 10 (11), 4750-4755 (2010).</li><li>Cai, J., Niu, 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=High-Performance+Supercapacitor+Electrode+Materials+from+Cellulose-Derived+Carbon+Nanofibers.">High-Performance Supercapacitor Electrode Materials from Cellulose-Derived Carbon Nanofibers.</a> ACS Appl Mat Interfaces. 7 (27), 14946-14953 (2015).</li><li>Joshi, P., Zhang, 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=Composite+of+TiO2+nanofibers+and+nanoparticles+for+dye-sensitized+solar+cells+with+significantly+improved+efficiency.">Composite of TiO2 nanofibers and nanoparticles for dye-sensitized solar cells with significantly improved efficiency.</a> Energ Environ Sci. 3 (10), 1507-1510 (2010).</li><li>Macdonald, T. J., Tune, D. D., Dewi, M. R., Gibson, C. T., Shapter, J. G., Nann, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+TiO2+Nanofiber-Carbon+Nanotube-Composite+Photoanode+for+Improved+Efficiency+in+Dye-Sensitized+Solar+Cells.">A TiO2 Nanofiber-Carbon Nanotube-Composite Photoanode for Improved Efficiency in Dye-Sensitized Solar Cells.</a> ChemSusChem. 8 (20), 3396-3400 (2015).</li><li>Teo, W. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Electrospinning parameters and fiber control. , (2015).</li></ol>

The methods presented in this work describe the fabrication of efficient nanofibrous photoanodes for photocatalytic devices such as DSSCs. Electrospinning is a very versatile technique for the fabrication of nanofibers, but a certain level of skill and knowledge is required to obtain materials with optimal morphologies. One of the most critical aspects to obtaining good nanofibers is the preparation of the precursor solution: there are some key factors, such as the concentration of the carrier polymer and the choice of t...

Dye-sensitized solar cells (DSSCs) are an interesting alternative to silicon-based solar cells1 thanks to their low cost, relatively simple manufacturing process, and ease of large-scale production. Another benefit is their potential to be incorporated into flexible substrates, a distinct advantage over silicon-based solar cells2. A typical DSSC utilizes: (1) a nanoparticulate TiO2 photoanode, sensitized with a dye, as a light-harvesting layer; (2) a Pt-coated FTO, used as a counter electrode; and (3) an electrolyte containing a redox couple, such as I-/I3-, placed between the two electrodes, working as a &#34;hole-conducting medium.&#34;
Although DSSCs have surpassed efficiencies of 15%3, the performance of nanoparticle-based photoanodes is still still hindered by a number of limitations, including slow electron mobility4, poor absorption of low-energy photons5, and charge recombination6. The electron collection efficiency strongly depends upon the rate of electron transport through the TiO2 nanoparticle layer. If the charge diffusion is slow, the probability of recombination with I3- in the electrolyte solution increases, resulting in a loss of efficiency.
It has been shown that replacing nanoparticulate TiO2 with one-dimensional (1D) TiO2 nanoarchitectures can improve charge transport by reducing the scattering of free electrons from the grain boundaries of the interconnected TiO2 nanoparticles7. As 1D nanostructures provide a more direct pathway for charge collection, we can expect that electron transport in nanofibers (NFs) would be significantly faster than in nanoparticles8,9.
Electrospinning is one of the most commonly used methods for the fabrication of fibrous materials with sub-micron diameters10. This technique involves the use of high voltage to induce the ejection of a polymer solution jet through a spinneret. Due to bending instability, this jet is subsequently stretched many times to form continuous nanofibers. In recent years, this technique has been extensively used to fabricate polymeric and inorganic materials, which have been used for numerous and diverse applications, such as tissue engineering11, catalysis12, and as electrode materials for lithium ion batteries13 and supercapacitors14.
The use of electrospun TiO2-NFs as the scattering layer in the photoanode can increase the performance of DSSCs. However, photoanodes with nanofibrous architectures tend to have poor dye absorption due to surface-area limitations. One of the possible solutions to overcome this is to mix NFs and nanoparticles. This has been shown to result in additional scattering layers, improving light absorption and overall efficiency15.
The protocol presented in this video provides a facile method to synthesize ultralong TiO2 nanofibers through a combination of electrospinning and sol-gel techniques, followed by a calcination process. The protocol then illustrates the use of the TiO2-NFs in combination with nanoparticulate TiO2 for the fabrication of a dual-layer photoanode with enhanced light-scattering capability using doctor blading techniques, as well as the subsequent assembly of a DSSC using such a photoanode.

<table border="0" cellpadding="0" cellspacing="0" width="689">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">titanium(IV) n-butoxide</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td align="right" style="width:127px;">244112</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Polyvinylpyrrolidone</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td align="right" style="width:127px;">437190</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">glacial acetic acid</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td style="width:127px;">A6283</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">Ethanol, absolute</td>
			<td style="width:149px;">Fisher Scientific</td>
			<td style="width:127px;">E/0650DF/17</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">20 mL Sample vials</td>
			<td style="width:149px;">(any)</td>
			<td style="width:127px;"></td>
			<td>(or larger volume)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">disposable 21G needle</td>
			<td style="width:149px;">(any)</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">P150 grit sandpaper</td>
			<td style="width:149px;">(any)</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">disposable 10mL syringe</td>
			<td style="width:149px;">(any)</td>
			<td style="width:127px;"></td>
			<td>(or larger volume)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">magnetic stirrer + stirring bar</td>
			<td style="width:149px;">(any)</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">PHD 2000 syringe pump</td>
			<td style="width:149px;">Harvard Apparatus</td>
			<td style="width:127px;">71-2002</td>
			<td>(or any other syringe pump capable of outputting a 1mL/hr flow</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">Aluminium foil</td>
			<td style="width:149px;">(any)</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">Stainless steel collector plate</td>
			<td style="width:149px;">(custom built)</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:247px;">High Voltage Power Source</td>
			<td style="width:149px;">Gamma High Voltage Research, Inc</td>
			<td style="width:127px;">ES30P-10W</td>
			<td>(or any other power supply capable of outputting +15 kV</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">Polycarbonate protective shield</td>
			<td style="width:149px;">(custom built)</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">Ceramic crucible</td>
			<td style="width:149px;">(any)</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">Muffle furnace</td>
			<td style="width:149px;">(any)</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">Titanium dioxide, nanopowder</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td align="right" style="width:127px;">718467</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">50 mL 1-neck round bottom flasks</td>
			<td style="width:149px;">(any)</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">bath sonicator</td>
			<td style="width:149px;">(any)</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">Terpineol</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">Rotary evaporator</td>
			<td style="width:149px;">(any)</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">FTO glass</td>
			<td style="width:149px;">Solaronix</td>
			<td>TCO30-10/LI</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">Adhesive tape</td>
			<td style="width:149px;">(any)</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">razor blade</td>
			<td style="width:149px;">(any)</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">SEM</td>
			<td style="width:149px;">JEOL</td>
			<td style="width:127px;">6500F</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">XRD</td>
			<td style="width:149px;">PANalytical&#160;</td>
			<td style="width:127px;">X&#39;pert Pro</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">Titanium Tetrachloride</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td align="right" style="width:127px;">89545</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">Ruthenizer&#160; 535-bisTBA</td>
			<td style="width:149px;">Solaronix</td>
			<td style="width:127px;">N719</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">sealing film</td>
			<td style="width:149px;">Dyesol</td>
			<td>Meltonix 1170-25</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">Pt-coated FTO</td>
			<td style="width:149px;">Solaronix</td>
			<td>TCO30-10/LI</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1-propyl-3-methylimidazolium iodide</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td align="right" style="width:127px;">49637</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">Iodine</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td align="right" style="width:127px;">207772</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">benzimidazole</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td align="right" style="width:127px;">194123</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">3-Methoxypropionitrile</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td align="right" style="width:127px;">65290</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">Digital source meter</td>
			<td style="width:149px;">Keithley</td>
			<td align="right" style="width:127px;">2400</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:247px;">Solar Simulator</td>
			<td style="width:149px;">Abet technologies</td>
			<td align="right" style="width:127px;">10500</td>
			<td></td>
		</tr>
	</tbody>
</table>

electrospinning of photocatalytic electrodes for dye-sensitized solar cells

This work demonstrates a protocol to fabricate a fiber-based photoanode for dye-sensitized solar cells, consisting of a light-scattering layer made of electrospun titanium dioxide nanofibers (TiO2-NFs) on top of a blocking layer made of commercially available titanium dioxide nanoparticles (TiO2-NPs). This is achieved by first electrospinning a solution of titanium (IV) butoxide, polyvinylpyrrolidone (PVP), and glacial acetic acid in ethanol to obtain composite PVP/TiO2 nanofibers. These are then calcined at 500 &#176;C to remove the PVP and to obtain pure anatase-phase titania nanofibers. This material is characterized using scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). The photoanode is prepared by first creating a blocking layer through the deposition of a TiO2-NPs/terpineol slurry on a fluorine-doped tin oxide (FTO) glass slide using doctor blading techniques. A subsequent thermal treatment is performed at 500 &#176;C. Then, the light-scattering layer is formed by depositing a TiO2-NFs/terpineol slurry on the same slide, using the same technique, and calcinating again at 500 &#176;C. The performance of the photoanode is tested by fabricating a dye-sensitized solar cell and measuring its efficiency through J-V curves under a range of incident light densities, from 0.25-1 Sun.

The TiO2 nanofibers were characterized using SEM, X-ray photoelectron spectroscopy (XPS), and XRD. The nanostructure of the photoanode was characterized using SEM. The performance of the assembled DSSC was tested using a solar simulator and a source measure unit.
The SEM image in Figure 1A shows that the nanofibers synthesized using this protocol have a porous structure and a high aspect ...

Watch this Scientific Journal Video about Electrospinning of Photocatalytic Electrodes for Dye-sensitized Solar Cells at JoVE.com

Electrospinning of Photocatalytic Electrodes for Dye-sensitized Solar Cells

The overall goal of this project was to use electrospinning to fabricate a photoanode with improved performance for dye-sensitized solar cells.

This work demonstrates a protocol to fabricate a fiber-based photoanode for dye-sensitized solar cells, consisting of a light-scattering layer made of ...

The overall goal of this work is to fabricate a photoanode for dye-sensitized solar cells with improved performance using electrospinning. Nanomaterials are great. They show chemical and physical properties that you cannot find in the corresponding bulk materials.However, if you try to make a device using nanomaterials, this become, can become quite difficult. In this video, we show how to fabricate one-dimensional inorganic nanofibres, and using them for a solar cell device. The directionality in the nanofibres causes the devices to have a much better performance compared with devices that just use nanocrystalline materials.To make the precursor solution, place 10 milliliters of absolute ethanol, one milliliter of glacial acetic acid, five grams of Titanium(II)oxide, and one gram of PVP into a sample vial. Mix the solution until it has become homogeneous and no bubbles can be observed. In order to obtain a one-dimensional nanoarchitecture, we're going to use electrospinning.A simple yet rather clever technique which allows us to obtain nanofibres with several micrometers in length and only few hundred nanometers in diameter. To prepare the needle used for the electrospinning process, cut the tip of a 21 gauge needle and sand it down using moderate grade sandpaper until the tip is completely flat. Load the precursor solution into the syringe and place it on the syringe pump.Wrap the collector plate with aluminum foil and place the protective shield around the setup. The distance between the needle and the collector plate should be 20 centimeters. Connect the collector to the ground and the needle to the power source.Set the flow rate of the syringe pump to one milliliter per hour, and begin pumping. As soon as some solution appears on the tip of the needle, turn on the high voltage source and set it to 15 kilovolts. At this point, fibers are going to collect on the plate.This can be left running for as long as necessary to achieve the desired thickness of the fiber mat. After the spinning is completed, turn off the high voltage source and remove the foil from the collector plate. Letting the fibers rest overnight makes it easier to peel them off the collector plate.Place the peeled off fibers in a crucible and place them in a furnace with a temperature ramp of five degrees per minute, up to 500 degrees for two hours to remove the PVP and produce pure TiO2 nanofibres. Fabrication of the photoanode requires that the position of a light-scattering layer consisting of titanium dioxide nanofibres on top of a blocking layer made of commercially available titanium dioxide nanoparticles. This is essential for preventing charge accumulation with a substrate.Start by adding 500 milligrams of titanium dioxide nanoparticles to 20 mils of ethanol in a round-bottom flask. In a separate flask, mix 500 milligrams of the electrospun titanium dioxide nanofibres with another 20 mils of ethanol. Sonicate the solutions for two hours using a bath sonicator.Once uniform mixtures are obtained, add 2 mils of terpineol to each flask, and sonicate for another 15 minutes. Finally, evaporate the solvent using a rotary evaporator to obtain the slurries. Using a diamond glass cutter, cut an FTO slide into a two by two centimeter square.Place adhesive tape on the glass slide, leaving a 0.4 square centimeter area, exposing the center. Deposit a few drops of the titanium dioxide nanoparticle slurry on the center of the glass slide. Use a razor blade to spread the slurry evenly on the exposed area.Once a uniform coating is achieved, carefully remove the adhesive tape. Photoanodes are then placed in a furnace and centered at 500 degrees for two hours. Repeat the process on the same glass slide, this time using the nanofibre slurry to deposit the light scattering layer.The composite photoanode is again centered at 500 degrees for two hours. To characterize our nanofibres, we are going to use SEM and XRD, and then to test the performance of our nanofibres, we are going to implement them in a dye-sensitized solar cell. To prepare the sample for scanning electron microscoping, attach a strip of adhesive carbon tape on the microscope stub.And then carefully place a small quantity of nanofibres on the tape. Mount the stub onto a sample holder and lower it into the exchange chamber of the instrument. Set up the instrument conditions and parameters accordingly.Collect images of the sample, making sure that they display the overall morphology of the material. The SEM images show that the fibers are porous in structure and have a high aspect ratio. To prepare the material for X-ray diffraction characterization, gently grind some nanofibres into a fine powder and spread them evenly on an XRD stage.Load the sample into the diffractometer. Set up the acquisition parameters and start collecting the data. The diffractogram shows a series of peaks corresponding to the anatase phase of titanium dioxide.To prepare the solar cell, first treat the TiO2 photoanodes with an aqueous solution of TiCl4 at 75 degrees C for 45 minutes. After treatment, wash the photoanodes with the ionized water. Dry them, and insensitize them in a solution of Ruthenizer N719 and absolute ethanol for 24 hours under dark conditions.The sensitized photoanodes will wash with ethanol to remove excess dye molecules from the TiO2 photoanode surface. Sealing film is used as a thermoplastic gasket between the counter electrode and the photoanodes. Counter electrodes of platinum-coated FTO are used for all solar cells.The assembled solar cells are heated to 100 degrees C for 15 minutes to seal the gasket. A redox mediator is added to the internal space of the solar cells by vacuum filling. J-V curves are acquired using a Keithley 2400 Digital SourceMeter under a 100 milowatt per centimeter square illumination from a xenon arc source passed through an AM 1.5 G filter.The illumination plane for the light source is calibrated with a monocrystalline silicon reference cell. In this video, we have shown you how to fabricate a dye-sensitized solar cells using inorganic nanofibres. On top of this application, there are many other possibilities.For example, batteries, transparent electrodes, active filters, and others. If you want to know more details, please have a look at our publications. I hope you enjoyed and learned from this video, and please contact us if you've got question or want to give any feedback.

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Research

JoVE Journal

Engineering

Polycrystalline Silicon Thin-film Solar cells with Plasmonic-enhanced Light-trapping

One of major approaches to cheaper solar cells is reducing the amount of semiconductor material used for their fabrication and making cells thinner. To compensate for lower light absorption such physically thin devices have to incorporate light-trapping which increases their optical thickness. Light scattering by textured surfaces is a common technique but it cannot be universally applied to all solar cell technologies. Some cells, for example those made of evaporated silicon, are planar as produced and they require an alternative light-trapping means suitable for planar devices. Metal nanoparticles formed on planar silicon cell surface and capable of light scattering due to surface plasmon resonance is an effective approach.
The paper presents a fabrication procedure of evaporated polycrystalline silicon solar cells with plasmonic light-trapping and demonstrates how the cell quantum efficiency improves due to presence of metal nanoparticles.
To fabricate the cells a film consisting of alternative boron and phosphorous doped silicon layers is deposited on glass substrate by electron beam evaporation. An Initially amorphous film is crystallised and electronic defects are mitigated by annealing and hydrogen passivation. Metal grid contacts are applied to the layers of opposite polarity to extract electricity generated by the cell. Typically, such a ~2 &mu;m thick cell has a short-circuit current density (Jsc) of 14-16 mA/cm2, which can be increased up to 17-18 mA/cm2 (~25% higher) after application of a simple diffuse back reflector made of a white paint.
To implement plasmonic light-trapping a silver nanoparticle array is formed on the metallised cell silicon surface. A precursor silver film is deposited on the cell by thermal evaporation and annealed at 23&deg;C to form silver nanoparticles. Nanoparticle size and coverage, which affect plasmonic light-scattering, can be tuned for enhanced cell performance by varying the precursor film thickness and its annealing conditions. An optimised nanoparticle array alone results in cell Jsc enhancement of about 28%, similar to the effect of the diffuse reflector. The photocurrent can be further increased by coating the nanoparticles by a low refractive index dielectric, like MgF2, and applying the diffused reflector. The complete plasmonic cell structure comprises the polycrystalline silicon film, a silver nanoparticle array, a layer of MgF2, and a diffuse reflector. The Jsc for such cell is 21-23 mA/cm2, up to 45% higher than Jsc of the original cell without light-trapping or ~25% higher than Jsc for the cell with the diffuse reflector only.
Introduction
Light-trapping in silicon solar cells is commonly achieved via light scattering at textured interfaces. Scattered light travels through a cell at oblique angles for a longer distance and when such angles exceed the critical angle at the cell interfaces the light is permanently trapped in the cell by total internal reflection (Animation 1: Light-trapping). Although this scheme works well for most solar cells, there are developing technologies where ultra-thin Si layers are produced planar (e.g. layer-transfer technologies and epitaxial c-Si layers) 1 and or when such layers are not compatible with textures substrates (e.g. evaporated silicon) 2. For such originally planar Si layer alternative light trapping approaches, such as diffuse white paint reflector 3, silicon plasma texturing 4 or high refractive index nanoparticle reflector 5 have been suggested.
Metal nanoparticles can effectively scatter incident light into a higher refractive index material, like silicon, due to the surface plasmon resonance effect 6. They also can be easily formed on the planar silicon cell surface thus offering a light-trapping approach alternative to texturing. For a nanoparticle located at the air-silicon interface the scattered light fraction coupled into silicon exceeds 95% and a large faction of that light is scattered at angles above critical providing nearly ideal light-trapping condition (Animation 2: Plasmons on NP). The resonance can be tuned to the wavelength region, which is most important for a particular cell material and design, by varying the nanoparticle average size, surface coverage and local dielectric environment 6,7. Theoretical design principles of plasmonic nanoparticle solar cells have been suggested 8. In practice, Ag nanoparticle array is an ideal light-trapping partner for poly-Si thin-film solar cells because most of these design principle are naturally met. The simplest way of forming nanoparticles by thermal annealing of a thin precursor Ag film results in a random array with a relatively wide size and shape distribution, which is particularly suitable for light-trapping because such an array has a wide resonance peak, covering the wavelength range of 700-900 nm, important for poly-Si solar cell performance. The nanoparticle array can only be located on the rear poly-Si cell surface thus avoiding destructive interference between incident and scattered light which occurs for front-located nanoparticles 9. Moreover, poly-Si thin-film cells do not requires a passivating layer and the flat base-shaped nanoparticles (that naturally result from thermal annealing of a metal film) can be directly placed on silicon further increases plasmonic scattering efficiency due to surface plasmon-polariton resonance 10.
The cell with the plasmonic nanoparticle array as described above can have a photocurrent about 28% higher than the original cell. However, the array still transmits a significant amount of light which escapes through the rear of the cell and does not contribute into the current. This loss can be mitigated by adding a rear reflector to allow catching transmitted light and re-directing it back to the cell. Providing sufficient distance between the reflector and the nanoparticles (a few hundred nanometers) the reflected light will then experience one more plasmonic scattering event while passing through the nanoparticle array on re-entering the cell and the reflector itself can be made diffuse - both effects further facilitating light scattering and hence light-trapping. Importantly, the Ag nanoparticles have to be encapsulated with an inert and low refractive index dielectric, like MgF2 or SiO2, from the rear reflector to avoid mechanical and chemical damage 7. Low refractive index for this cladding layer is required to maintain a high coupling fraction into silicon and larger scattering angles, which are ensured by the high optical contrast between the media on both sides of the nanoparticle, silicon and dielectric 6. The photocurrent of the plasmonic cell with the diffuse rear reflector can be up to 45% higher than the current of the original cell or up to 25% higher than the current of an equivalent cell with the diffuse reflector only.

Polycrystalline silicon thin-film solar cells on glass are fabricated by deposition of boron and phosphorous doped silicon layers followed by crystallisation, defect passivation and metallisation. Plasmonic light-trapping is introduced by forming Ag nanoparticles on the silicon cell surface capped with a diffused reflector resulting in ~45% photocurrent enhancement.

One of major approaches to cheaper solar cells is reducing the amount of semiconductor material used for their fabrication and making cells thinner. To ...

Harvesting Solar Energy by Means of Charge-Separating Nanocrystals and Their Solids

Conjoining different semiconductor materials in a single nano-composite provides synthetic means for the development of novel optoelectronic materials offering a superior control over the spatial distribution of charge carriers across material interfaces. As this study demonstrates, a combination of donor-acceptor nanocrystal (NC) domains in a single nanoparticle can lead to the realization of efficient photocatalytic1-5 materials, while a layered assembly of donor- and acceptor-like nanocrystals films gives rise to photovoltaic materials.
Initially the paper focuses on the synthesis of composite inorganic nanocrystals, comprising linearly stacked ZnSe, CdS, and Pt domains, which jointly promote photoinduced charge separation. These structures are used in aqueous solutions for the photocatalysis of water under solar radiation, resulting in the production of H2 gas. To enhance the photoinduced separation of charges, a nanorod morphology with a linear gradient originating from an intrinsic electric field is used5. The inter-domain energetics are then optimized to drive photogenerated electrons toward the Pt catalytic site while expelling the holes to the surface of ZnSe domains for sacrificial regeneration (via methanol). Here we show that the only efficient way to produce hydrogen is to use electron-donating ligands to passivate the surface states by tuning the energy level alignment at the semiconductor-ligand interface. Stable and efficient reduction of water is allowed by these ligands due to the fact that they fill vacancies in the valence band of the semiconductor domain, preventing energetic holes from degrading it. Specifically, we show that the energy of the hole is transferred to the ligand moiety, leaving the semiconductor domain functional. This enables us to return the entire nanocrystal-ligand system to a functional state, when the ligands are degraded, by simply adding fresh ligands to the system4.
To promote a photovoltaic charge separation, we use a composite two-layer solid of PbS and TiO2 films. In this configuration, photoinduced electrons are injected into TiO2 and are subsequently picked up by an FTO electrode, while holes are channeled to a Au electrode via PbS layer6. To develop the latter we introduce a Semiconductor Matrix Encapsulated Nanocrystal Arrays (SMENA) strategy, which allows bonding PbS NCs into the surrounding matrix of CdS semiconductor. As a result, fabricated solids exhibit excellent thermal stability, attributed to the heteroepitaxial structure of nanocrystal-matrix interfaces, and show compelling light-harvesting performance in prototype solar cells7.

A general strategy for the development of charge-separating semiconductor nanocrystal composites deployable for solar energy production is presented. We show that assembly of donor-acceptor nanocrystal domains in a single nanoparticle geometry gives rise to a photocatalytic function, while bulk-heterojunctions of donor-acceptor nanocrystal films can be used for photovoltaic energy conversion.

Conjoining different semiconductor materials in a single nano-composite provides synthetic means for the development of novel optoelectronic materials ...

Integrating a Triplet-triplet Annihilation Up-conversion System to Enhance Dye-sensitized Solar Cell Response to Sub-bandgap Light

The poor response of dye-sensitized solar cells (DSCs) to red and infrared light is a significant impediment to the realization of higher photocurrents and hence higher efficiencies. Photon up-conversion by way of triplet-triplet annihilation (TTA-UC) is an attractive technique for using these otherwise wasted low energy photons to produce photocurrent, while not interfering with the photoanodic performance in a deleterious manner. Further to this, TTA-UC has a number of features, distinct from other reported photon up-conversion technologies, which renders it particularly suitable for coupling with DSC technology. In this work, a proven high performance TTA-UC system, comprising a palladium porphyrin sensitizer and rubrene emitter, is combined with a high performance DSC (utilizing the organic dye D149) in an integrated device. The device shows an enhanced response to sub-bandgap light over the absorption range of the TTA-UC sub-unit resulting in the highest figure of merit for up-conversion assisted DSC performance to date.

An integrated device, incorporating a dye-sensitized solar cell and triplet-triplet annihilation up-conversion unit was produced, affording enhanced light harvesting, from a wider section of the solar spectrum. Under modest irradiation levels a significantly enhanced response to low energy photons was demonstrated, yielding a record figure of merit for dye-sensitized solar cells.

The poor response of dye-sensitized solar cells (DSCs) to red and infrared light is a significant impediment to the realization of higher photocurrents ...

Ambient Method for the Production of an Ionically Gated Carbon Nanotube Common Cathode in Tandem Organic Solar Cells

A method of fabricating organic photovoltaic (OPV) tandems that requires no vacuum processing is presented. These devices are comprised of two solution-processed polymeric cells connected in parallel by a transparent carbon nanotubes (CNT) interlayer. This structure includes improvements in fabrication techniques for tandem OPV devices. First the need for ambient-processed cathodes is considered. The CNT anode in the tandem device is tuned via ionic gating to become a common cathode. Ionic gating employs electric double layer charging to lower the work function of the CNT electrode. Secondly, the difficulty of sequentially stacking tandem layers by solution-processing is addressed. The devices are fabricated via solution and dry-lamination in ambient conditions with parallel processing steps. The method of fabricating the individual polymeric cells, the steps needed to laminate them together with a common CNT cathode, and then provide some representative results are described. These results demonstrate ionic gating of the CNT electrode to create a common cathode and addition of current and efficiency as a result of the lamination procedure.

A method of fabricating, in ambient conditions, organic photovoltaic tandem devices in a parallel configuration is presented. These devices feature an air-processed, semi-transparent, carbon nanotube common cathode.

A method of fabricating organic photovoltaic (OPV) tandems that requires no vacuum processing is presented. These devices are comprised of two ...

Making Record-efficiency SnS Solar Cells by Thermal Evaporation and Atomic Layer Deposition

Tin sulfide (SnS) is a candidate absorber material for Earth-abundant, non-toxic solar cells. SnS offers easy phase control and rapid growth by congruent thermal evaporation, and it absorbs visible light strongly. However, for a long time the record power conversion efficiency of SnS solar cells remained below 2%. Recently we demonstrated new certified record efficiencies of 4.36% using SnS deposited by atomic layer deposition, and 3.88% using thermal evaporation. Here the fabrication procedure for these record solar cells is described, and the statistical distribution of the fabrication process is reported. The standard deviation of efficiency measured on a single substrate is typically over 0.5%. All steps including substrate selection and cleaning, Mo sputtering for the rear contact (cathode), SnS deposition, annealing, surface passivation, Zn(O,S) buffer layer selection and deposition, transparent conductor (anode) deposition, and metallization are described. On each substrate we fabricate 11 individual devices, each with active area 0.25 cm2. Further, a system for high throughput measurements of current-voltage curves under simulated solar light, and external quantum efficiency measurement with variable light bias is described. With this system we are able to measure full data sets on all 11 devices in an automated manner and in minimal time. These results illustrate the value of studying large sample sets, rather than focusing narrowly on the highest performing devices. Large data sets help us to distinguish and remedy individual loss mechanisms affecting our devices.

Tin sulfide (SnS) is a candidate material for Earth-abundant, non-toxic solar cells. Here, we demonstrate the fabrication procedure of the SnS solar cells employing atomic layer deposition, which yields 4.36% certified power conversion efficiency, and thermal evaporation which yields 3.88%.

Tin sulfide (SnS) is a candidate absorber material for Earth-abundant, non-toxic solar cells. SnS offers easy phase control and rapid growth by congruent ...

Integration of Light Trapping Silver Nanostructures in Hydrogenated Microcrystalline Silicon Solar Cells by Transfer Printing

One of the potential applications of metal nanostructures is light trapping in solar cells, where unique optical properties of nanosized metals, commonly known as plasmonic effects, play an important role. Research in this field has, however, been impeded owing to the difficulty of fabricating devices containing the desired functional metal nanostructures. In order to provide a viable strategy to this issue, we herein show a transfer printing-based approach that allows the quick and low-cost integration of designed metal nanostructures with a variety of device architectures, including solar cells. Nanopillar poly(dimethylsiloxane) (PDMS) stamps were fabricated from a commercially available nanohole plastic film as a master mold. On this nanopatterned PDMS stamps, Ag films were deposited, which were then transfer-printed onto block copolymer (binding layer)-coated hydrogenated microcrystalline Si (&#181;c-Si:H) surface to afford ordered Ag nanodisk structures. It was confirmed that the resulting Ag nanodisk-incorporated &#181;c-Si:H solar cells show higher performances compared to a cell without the transfer-printed Ag nanodisks, thanks to plasmonic light trapping effect derived from the Ag nanodisks. Because of the simplicity and versatility, further device application would also be feasible thorough this approach.

A viable transfer printing-based methodology to introduce plasmonic metal nanostructures in solar cells is described. Using nanopillar poly(dimethylsiloxane) stamps, an Ag-based ordered nanodisk array was integrated with standard hydrogenated microcrystalline Si solar cells, which led to improved device performances due to plasmonic light trapping.

One of the potential applications of metal nanostructures is light trapping in solar cells, where unique optical properties of nanosized metals, commonly ...

Printing Fabrication of Bulk Heterojunction Solar Cells and In Situ Morphology Characterization

Polymer-based materials hold promise as low-cost, flexible efficient photovoltaic devices. Most laboratory efforts to achieve high performance devices have used devices prepared by spin coating, a process that is not amenable to large-scale fabrication. This mismatch in device fabrication makes it difficult to translate quantitative results obtained in the laboratory to the commercial level, making optimization difficult. Using a mini-slot die coater, this mismatch can be resolved by translating the commercial process to the laboratory and characterizing the structure formation in the active layer of the device in real time and in situ as films are coated onto a substrate. The evolution of the morphology was characterized under different conditions, allowing us to propose a mechanism by which the structures form and grow. This mini-slot die coater offers a simple, convenient, material efficient route by which the morphology in the active layer can be optimized under industrially relevant conditions. The goal of this protocol is to show experimental details of how a solar cell device is fabricated using a mini-slot die coater and technical details of running in situ structure characterization using the mini-slot die coater.

Printing Fabrication of Bulk Heterojunction Solar Cells and In Situ Morphology Characterization

Here, we present a protocol to fabricate organic thin film solar cells using a mini-slot die coater and related in-line structure characterizations using synchrotron scattering techniques.

Polymer-based materials hold promise as low-cost, flexible efficient photovoltaic devices. Most laboratory efforts to achieve high performance devices ...

Digital Printing of Titanium Dioxide for Dye Sensitized Solar Cells

Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less environmentally damaging with lower processing temperatures presenting a viable and low cost alternative to conventional production. This paper further enhances these environmental credentials by evaluating the digital printing and therefore additive production route for these cells. This is achieved here by investigating the formation and performance of a metal oxide photoelectrode using nanoparticle sized titanium dioxide. An ink-jettable material was formulated, characterized and printed with a piezoelectric inkjet head to produce a 2.6 &#181;m thick layer. The resultant printed layer was fabricated into a functioning cell with an active area of 0.25 cm2 and a power conversion efficiency of 3.5%. The binder-free formulation resulted in a reduced processing temperature of 250 &#176;C, compatible with flexible polyamide substrates which are stable up to temperatures of 350 &#730;C. The authors are continuing to develop this process route by investigating inkjet printing of other layers within dye sensitized solar cells.

This paper investigates the suitability of inkjet printing for the manufacturing of dye-sensitized solar cells. A binder-free TiO2 nanoparticle ink was formulated and printed onto a FTO glass substrate. The printed layer was fabricated into a cell with an active area of 0.25 cm2 and an efficiency of 3.5%.

Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less ...

Monovalent Cation Doping of CH3NH3PbI3 for Efficient Perovskite Solar Cells

Here, we demonstrate the incorporation of monovalent cation additives into CH3NH3PbI3 perovskite in order to adjust the optical, excitonic, and electrical properties. The possibility of doping was investigated by adding monovalent cation halides with similar ionic radii to Pb2+, including Cu+, Na+, and Ag+. A shift in the Fermi level and a remarkable decrease of sub-bandgap optical absorption, along with a lower energetic disorder in the perovskite, was achieved. An order-of-magnitude enhancement in the bulk hole mobility and a significant reduction of transport activation energy within an additive-based perovskite device was attained. The confluence of the aforementioned improved properties in the presence of these cations led to an enhancement in the photovoltaic parameters of the perovskite solar cell. An increase of 70 mV in open circuit voltage for AgI and a 2 mA/cm2 improvement in photocurrent density for NaI- and CuBr-based solar cells were achieved compared to the pristine device. Our work paves the way for further improvements in the optoelectronic quality of CH3NH3PbI3 perovskite and subsequent devices. It highlights a new avenue for investigations on the role of dopant impurities in crystallization and controls the electronic defect density in perovskite structures.

Monovalent Cation Doping of CH3NH3PbI3 for Efficient Perovskite Solar Cells

Here, we present a protocol to adjust the properties of solution-processed CH3NH3PbI3 through the incorporation of monovalent cation additives in order to achieve highly efficient perovskite solar cells.

Here, we demonstrate the incorporation of monovalent cation additives into CH3NH3PbI3 perovskite in order to adjust the optical, excitonic, and electrical ...

In Situ Monitoring of the Accelerated Performance Degradation of Solar Cells and Modules: A Case Study for Cu(In,Ga)Se2 Solar Cells

The levelized cost of electricity (LCOE) of photovoltaic (PV) systems is determined by, among other factors, the PV module reliability. Better prediction of degradation mechanisms and prevention of module field failure can consequently decrease investment risks as well as increase the electricity yield. An improved knowledge level can for these reasons significantly decrease the total costs of PV electricity. 
In order to better understand and minimize the degradation of PV modules, the occurring degradation mechanisms and conditions should be identified. This should preferably happen under combined stresses, since modules in the field are also simultaneously exposed to multiple stress factors. Therefore, two 'Combined Stress test with in situ measurement' setups have been designed and constructed. These setups allow the simultaneous use of humidity, temperature, illumination, and electrical biases as independently controlled stress factors on solar cells and minimodules. The setups also allow real-time monitoring of the electrical properties of these samples. This protocol presents these setups and describes the experimental possibilities. Moreover, results obtained with these setups are also presented: various examples about the influence of both deposition and degradation conditions on the stability of thin film Cu(In,Ga)Se2 (CIGS) as well as Cu2ZnSnSe4 (CZTS) solar cells are described. Results on the temperature dependency of CIGS solar cells are also presented.

In Situ Monitoring of the Accelerated Performance Degradation of Solar Cells and Modules: A Case Study for CuIn,GaSe2 Solar Cells

Two &#39;Combined Stress test with in situ measurement&#39; setups, which allow real-time monitoring of accelerated degradation of solar cells and modules, were designed and constructed. These setups allow the simultaneous use of humidity, temperature, electrical biases, and illumination as independently controlled stress factors. The setups and various experiments executed are presented.

The levelized cost of electricity (LCOE) of photovoltaic (PV) systems is determined by, among other factors, the PV module reliability. Better prediction ...