This work is supported by the Natural Science Foundation of China (No. 21506194, 21676255).

Caution: Please consult all relevant Material Safety Data Sheets (MSDS) before operation. Several chemicals are flammable and highly corrosive. Concentrating light can cause harmful light intensity and temperature increases. Please use all appropriate safety devices such as personal protective equipment (safety glasses, gloves, lab coats, pants, etc.).
1. Catalyst Preparation
<ol>
	<li>Preparation of TiO2 by anodization 
	Note: Anodization uses metal...

<ol>
	<li>De-Richter, R. K., Ming, T., Caillol, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fighting+global+warming+by+photocatalytic+reduction+of+CO2,+using+giant+photocatalytic+reactors.">Fighting global warming by photocatalytic reduction of CO2, using giant photocatalytic reactors.</a> Renewable &amp; Sustainable Energy Reviews. 19 (1), 82-106 (2013).</li><li>Fang, Y., Wang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photocatalytic+CO2+conversion+by+polymeric+carbon+nitrides.">Photocatalytic CO2 conversion by polymeric carbon nitrides.</a> Chemical Communications. 54 (45), 5674-5687 (2018).</li><li>Kondratenko, E. V., 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=Status+and+perspectives+of+CO2+conversion+into+fuels+and+chemicals+by+catalytic,+photocatalytic+and+electrocatalytic+processes.">Status and perspectives of CO2 conversion into fuels and chemicals by catalytic, photocatalytic and electrocatalytic processes.</a> Energy &amp; Environmental Science. 6 (11), 3112-3135 (2013).</li><li>Izumi, Y., Jin, F., He, L. -. N., Hu, Y. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+Advances+(2012-2015)+in+the+Photocatalytic+Conversion+of+Carbon+Dioxide+to+Fuels+Using+Solar+Energy:+Feasibilty+for+a+New+Energy.">Recent Advances (2012-2015) in the Photocatalytic Conversion of Carbon Dioxide to Fuels Using Solar Energy: Feasibilty for a New Energy.</a> Advances in CO2 Capture, Sequestration, and Conversion. , 1-46 (2015).</li><li>White, J. 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=Light-Driven+Heterogeneous+Reduction+of+Carbon+Dioxide:+Photocatalysts+and+Photoelectrodes.">Light-Driven Heterogeneous Reduction of Carbon Dioxide: Photocatalysts and Photoelectrodes.</a> Chemical Reviews. 115 (23), 12888-12935 (2015).</li><li>Habisreutinger, S. N., Schmidtmende, L., Stolarczyk, J. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photocatalytic+Reduction+of+CO2+on+TiO2+and+Other+Semiconductors.">Photocatalytic Reduction of CO2 on TiO2 and Other Semiconductors.</a> Angewandte Chemie International Edition. 52 (29), 7372-7408 (2013).</li><li>Weinstein, L. A., 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=Concentrating+Solar+Power.">Concentrating Solar Power.</a> Chemical Reviews. 115 (23), 12797-12838 (2015).</li><li>Herrmann, J. M., 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=TiO2+-based+solar+photocatalytic+detoxification+of+water+containing+organic+pollutants.+Case+studies+of+2,+4-dichlorophenoxyaceticacid+(2,+4+-+D)+and+of+benzofuran.">TiO2 -based solar photocatalytic detoxification of water containing organic pollutants. Case studies of 2, 4-dichlorophenoxyaceticacid (2, 4 - D) and of benzofuran.</a> Applied Catalysis B Environmental. 17 (1-2), 15-23 (1998).</li><li>Zeng, 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=Combined+effects+of+initial+water+content+and+heating+parameters+on+solar+pyrolysis+of+beech+wood.">Combined effects of initial water content and heating parameters on solar pyrolysis of beech wood.</a> Energy. 125, 552-561 (2017).</li><li>Zeng, 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=Characterization+of+solar+fuels+obtained+from+beech+wood+solar+pyrolysis.">Characterization of solar fuels obtained from beech wood solar pyrolysis.</a> Fuel. 188, 285-293 (2017).</li><li>Nguyen, T. V., Wu, J. C. S., Chiou, C. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photoreduction+of+CO+over+Ruthenium+dye-sensitized+TiO-based+catalysts+under+concentrated+natural+sunlight.">Photoreduction of CO over Ruthenium dye-sensitized TiO-based catalysts under concentrated natural sunlight.</a> Catalysis Communications. 9 (10), 2073-2076 (2008).</li><li>Guan, G., 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=Photoreduction+of+carbon+dioxide+with+water+over+K2Ti6O13,+photocatalyst+combined+with+Cu/ZnO+catalyst+under+concentrated+sunlight.">Photoreduction of carbon dioxide with water over K2Ti6O13, photocatalyst combined with Cu/ZnO catalyst under concentrated sunlight.</a> Applied Catalysis A: General. 249 (1), 11-18 (2003).</li><li>Han, S., Chen, Y. F., Abanades, S., Zhang, Z. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improving+photoreduction+of+CO2+with+water+to+CH4+in+a+novel+concentrated+solar+reactor.">Improving photoreduction of CO2 with water to CH4 in a novel concentrated solar reactor.</a> Journal of Energy Chemistry. 26 (4), 743-749 (2017).</li><li>Roy, S. 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=Toward+solar+fuels:+photocatalytic+conversion+of+carbon+dioxide+to+hydrocarbons.">Toward solar fuels: photocatalytic conversion of carbon dioxide to hydrocarbons.</a> ACS Nano. 4 (3), 1259-1278 (2010).</li><li>Li, D., Chen, Y. F., Abanades, S., Zhang, Z. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+activity+of+TiO2+by+concentrating+light+for+photoreduction+of+CO2+with+H2O+to+CH4.">Enhanced activity of TiO2 by concentrating light for photoreduction of CO2 with H2O to CH4.</a> Catalysis Communications. 113, 6-9 (2018).</li></ol>

Concentrating light reduces the light incident area and requires the use of a disc-shaped catalyst or a so-called fixed-bed reactor to hold the catalyst. Since the light source is usually a round-shaped lamp, the shape of the catalyst should also be round. To obtain a round disc, it is possible to press the powder into a disk by tableting or to change the metal foil into an oxide by anodization. The anodization method uses electricity to oxidize the metal to an oxide semiconductor. As the metal precursor is already a she...

The utilization of fossil fuels is accompanied by large amounts of CO2 emission, contributing greatly to global warming. CO2 capture, storage, and conversion are essential to reduce the CO2 content in the atmosphere1. The photoreduction of CO2 to hydrocarbons can reduce CO2, convert CO2 to fuels, and save solar energy. However, CO2 is an extremely stable molecule. Its C=O bond possesses a higher dissociation energy (about 750 kJ/mol)2. This means that CO2 is very hard to be activated and transformed, and only short wavelength lights with high energy can be functional during the process. Therefore, CO2 photoreduction studies suffer from low conversion efficiencies and reaction rates at present. Most reported CH4 yield rates are only at several &#181;mol&#183;gcata-1&#183;h-1 levels on a TiO2 catalyst3,4. The design and fabrication of photocatalytic systems with high conversion efficiency and reaction rate for CO2 reduction remain a challenge.
One popular area of research into CO2 photoreduction catalysts is to broaden the available light band to the visible spectrum and enhance the utilization efficiency of these wavelengths5,6. Instead, in this manuscript, we try to increase the reaction rate by enhancing the light intensity. As the driving force of a photocatalytic reaction is solar light, the basic idea is to use concentration technology to raise the incident solar light intensity and, therefore, increase the reaction rate. This is similar to a thermocatalytic process, where the reaction rate can be increased by increasing the temperature. Of course, the temperature effect cannot be not increased infinitely, and likewise with the light intensity; a major goal of this research is to find a suitable light intensity or concentration ratio.
This is not the first experiment that uses concentrating technology. In fact, it has been widely used in concentrating solar power and waste water treatment7,8. Biomaterials such as beech wood sawdust can be pyrolyzed in a solar reactor9,10. Some previous reports have mentioned the method for CO2 photoreduction11,12,13. One sample exhibited a 50% increment in the product yield when the light intensity was doubled14. Our group has found that concentrating light can raise CH4 yield rate with an up to 12-fold increase in intensity. In addition, pretreatment of catalyst before reaction by concentrating light can further increase the CH4 yield rate15. Here, we demonstrate the experimental system and method in detail.

<table>
	<tbody>
		<tr>
			<td>Ti foil, 99.99%</td>
			<td>Hebei Metal Technology Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pt foil, 99.99%</td>
			<td>Tianjin Aida Henghao Technology Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium fluoride, 98%</td>
			<td>Aladdin</td>
			<td>A111758</td>
			<td>Humidity sensitive</td>
		</tr>
		<tr>
			<td>Glycol, &#62;99.9%</td>
			<td>Aladdin</td>
			<td>E103323</td>
			<td></td>
		</tr>
		<tr>
			<td>Anhydrous ethanol,&#62;99.9%</td>
			<td>Aladdin</td>
			<td>E111977</td>
			<td>Flammable</td>
		</tr>
		<tr>
			<td>Acetone, &#62;99.5%</td>
			<td>Hangzhou Shuanglin Chemical Co., Ltd.</td>
			<td>200-662-2</td>
			<td>Irritating smell</td>
		</tr>
		<tr>
			<td>Nitric acid, 65.0%-68.0%</td>
			<td>Hangzhou Shuanglin Chemical Co., Ltd.</td>
			<td>231-714-2</td>
			<td>Humidity sensitive</td>
		</tr>
		<tr>
			<td>Hydrogen peroxide, 30 wt. % in H2O</td>
			<td>Aladdin</td>
			<td>H112515</td>
			<td>Strong oxidative</td>
		</tr>
		<tr>
			<td>Urea, 99%</td>
			<td>Aladdin</td>
			<td>U111897</td>
			<td></td>
		</tr>
		<tr>
			<td>De-ionized water, 99.00%</td>
			<td>Laboratory made</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Xe lamp, CELHXF300/CELHXUV300</td>
			<td>Beijing Zhongjiao Jinyuan Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Stainless cylinder reactor, CEL-GPPC</td>
			<td>Beijing Zhongjiao Jinyuan Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Fresnel lens, MYlens</td>
			<td>Meiying Technology Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>7000 mesh sandpaper</td>
			<td>Zibo Taichuan Abrasives Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ultrasonic cleaner, SK2210HP</td>
			<td>Shanghai Kedao Ultrasonic Instrument Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Thermostatical water bath, DF-101S</td>
			<td>Boncie Instrument Technology Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Alligator clip</td>
			<td>Guangzhou Rongyu Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>DC constant voltage source, DY-150V 2A</td>
			<td>Shanghai Anding Electric Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Muffle furnace, KSL-1200X</td>
			<td>Hefei Kejing Materials Technolgy Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Quartz glass</td>
			<td>Lianyungang Weida Quartz Products Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Thermocouples, WRNK-191K</td>
			<td>Feiyang Electric Accessories Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Electronmagnetic stirrer, 85-2</td>
			<td>Shanghai Zhiwei Electric Appliance Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum pump,SHB-IIIA</td>
			<td>Henan Province Taikang science and education equipment factory</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Gas Chromatograph, GC2014</td>
			<td>SHIMAPZU</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>HT-PLOT Q capillary column</td>
			<td>Hychrom</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Optical power meter,CEL-NP2000</td>
			<td>Beijing Zhongjiao Jinyuan Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Electronic scale, JJ124BC</td>
			<td>Shanghai Jingtian Electronic Instrument Co., Ltd.</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

co2 photoreduction to ch4 performance under concentrating solar light

We demonstrate a method for the enhancement of CO2 photoreduction. As the driving force of a photocatalytic reaction is from solar light, the basic idea is to use concentration technology to raise the incident solar light intensity. Concentrating a large-area light onto a small area cannot only increase light intensity, but also reduce the catalyst amount, as well as the reactor volume, and increase the surface temperature. The concentration of light can be realized by different devices. In this manuscript, it is realized by a Fresnel lens. The light penetrates the lens and is concentrated on a disc-shaped catalyst. The results show that both the reaction rate and the total yield are efficiently increased. The method can be applied to most CO2 photoreduction catalysts, as well as to similar reactions with a low reaction rate at natural light.

The original photocatalytic reactor system mainly contains two components, a Xe lamp and a stainless cylinder reactor. For the concentrating light reactor system, we added a Fresnel lens and a catalyst holder, as shown in Figure 1. The Fresnel lens is used to concentrate the light in a smaller area. As the light has been concentrated, the catalyst must be placed in a lit area; therefore, the catalyst is made into disc shape, and a holder is used to hold the c...

Watch this Scientific Journal Video about CO2 Photoreduction to CH4 Performance Under Concentrating Solar Light at JoVE.com

CO2 Photoreduction to CH4 Performance Under Concentrating Solar Light

We present a protocol for improving the performance of CO2 photoreduction to CH4 by heightening the incident light intensity via concentrating solar energy technology.

CO2 Photoreduction to CH4 Performance Under Concentrating Solar Light

We demonstrate a method for the enhancement of CO2 photoreduction. As the driving force of a photocatalytic reaction is from solar light, the basic idea ...

This method can help answer key questions in the artificial photosynthesis field, such as carbon dioxide photoreduction to methane. Concentrating technology can not only increase the light intensity but also reduce the catalyst amount as well as the reactor volume, while increasing the reaction temperature, thereby increasing the photoreduction reaction rate. Though this method can provide insight into photocatalytic reduction of carbon dioxide, it can also be applied to other systems such as concentrating solar power and wastewater treatment.To prepare the titanium dioxide by anodization dissolve 0.3 grams of ammonium fluoride and two milliliters of water into 100 milliliters of glycol in a 200 milliliter beaker with a stirrer to form the electrolyte. Place the beaker with the electrolyte into a 45 degree celsius water bath. Trim the titanium foil with scissors to 25 by 25 millimeters then polish the titanium foil surface with a 7000 mesh sand paper to remove the surface impurities.Submerge the titanium foil in a volumetric flask containing 15 milliliters of ethanol and then a flask with 15 milliliters of acetone. Now treat the foil for 15 minutes with an ultrasonic cleaner. Take out the titanium foil, rinse it three to five times with the ionized water and place it in a volumetric flask containing 20 milliliters of ethanol.Prepare the polishing solution in a 100 milliliter beaker as described in the text protocol. Now remove the titanium foil from the ethanol flask, rinse it three times with the ionized water and put it into the polishing solution for two to thee minutes. Remove the titanium foil and wash it with the ionized water an additional three times.Use an anoid alligator clip to hold the pretreated titanium foil and a cathode clip to hold a platinum foil. Place the two foils face to face in the electrolyte at a distance of two centimeters from each other. Turn on the direct current stabilized current power source, tune the voltage to 50 volts and electrolyze for 30 minutes.After the anodization has finished turn off the power and take out the titanium dioxide foil. Submerge the titanium foil in a volumetric flask containing 15 milliliters of ethanol and then transfer to a flask with 15 milliliters of acetone. Treat the titanium foil for 15 minutes with an ultrasonic cleaner.Following treatment, rinse the titanium foil three to five times with the ionized water and place it in 15 milliliter crucible. Put the crucible in an oven at 60 degrees Celsius for 12 hours to let the foil dry. Once dry, calcine the titanium dioxide foil in a muffle furnace under 400 degree Celsius for two hours with a heating rate of two degree Celsius per minute.To perform catalytic tests under concentrating light, clean the stainless cylinder shaped reactor with the ionized water. Then dry it in an oven at 60 degree Celsius for 10 minutes to ensure no interference from other carbon sources. After drying in the oven, add two milliliters of water, a stirrer and a catalyst holder to the reactor.Place a quartz glass with pours on the bottom of the holder and place the titanium dioxide catalysts on the center of the quartz glass. Now put thermal cup hole through an opening in the reactor wall and onto the catalyst surface. Add a Fresno lens on the top of the holder and seal the reactor with a quartz glass window.Place the reactor on the electromagnetic apparatus and check the air tightness with nitrogen. Feed the carbon dioxide into the reactor through a mass flow controller and flush the reactor at least three times to change the gas in the reactor to carbon dioxide. Place the Xenon lamp two centimeters directly above the reactor.Power on the Xenon lamp and adjust it's current to 15 amps then turn on the magnetic stirrers switch to start the reaction. Record the temperature change on the catalyst surface and in the gas. Analyze the product every hour using gas chromatography equipped with the flame ionized detector and a capillary column for separation of hydro carbons with one to six carbons.Calculate the number of products by the the external standard line method. Before quantifying the product build a standard curve of methane. Shown here is a device for concentrating photocatalytic reduction of carbon dioxide.XRD and SEM characterization of the catalyst showed that the prepared catalyst was a typical titanium oxide nanotube. Shown here is the catalyst under natural light. Under concentrating light the catalyst shows some shining.Here the x-ray diffraction pattern is shown, after concentrating light irradiation, to reveal crystal structure changes. The crystallinity is clearly improved after reaction under concentrating light. Methane yield is measured under natural and under concentrating light.The reaction rates of methane on different catalyst were significantly improved under the concentrating conditions. Pre-treatment of the catalyst with suitable gas would further increase the methane production rate. Following this procedure, other methods like concentrated photocatalysis under real sunlight can be performed in order to answer addition questions like photocatalytic splitting of water, and degradation of volatile organic compounds under real sunlight.After it's development, this technique paved the way for researchers in the photocatalytic field how to improve carbon dioxide photoreduction behavior in a photochemical system. Don't forget that working with concentrating light can be extremely hazardous and precautions such as googles should always be taken while performing this procedure.

co2-photoreduction-to-ch4-performance-under-concentrating-solar-light

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 ...

Using Neutron Spin Echo Resolved Grazing Incidence Scattering to Investigate Organic Solar Cell Materials

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped crystallites. Neutrons are passed through two well defined regions of magnetic field; one before and one after the sample. The two magnetic field regions have opposite polarity and are tuned such that neutrons travelling through both regions, without being perturbed, will undergo the same number of precessions in opposing directions. In this case the neutron precession in the second arm is said to &#34;echo&#34; the first, and the original polarization of the beam is preserved. If the neutron interacts with a sample and scatters elastically the path through the second arm is not the same as the first and the original polarization is not recovered. Depolarization of the neutron beam is a highly sensitive probe at very small angles (&#60;50&#160;&#956;rad) but still allows a high intensity, divergent beam to be used. The decrease in polarization of the beam reflected from the sample as compared to that from the reference sample can be directly related to structure within the sample.
In comparison to scattering observed in neutron reflection measurements the SERGIS signals are often weak and are unlikely to be observed if the in-plane structures within the sample under investigation are dilute, disordered, small in size and polydisperse or the neutron scattering contrast is low. Therefore, good results will most likely be obtained using the SERGIS technique if the sample being measured consist of thin films on a flat substrate and contain scattering features that contains a high density of moderately sized features (30 nm to 5 &#181;m) which scatter neutrons strongly or the features are arranged on a lattice. An advantage of the SERGIS technique is that it can probe structures in the plane of the sample.

Progress has been made in utilizing spin echo resolved grazing incidence scattering (SERGIS) as a neutron scattering technique to probe the length-scales in irregular samples. Crystallites of [6,6]-phenyl-C61-butyric acid methyl ester have been probed using the SERGIS technique and the results confirmed by optical and atomic force microscopy.

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped ...

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 ...

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 ...

Experimental Protocol to Investigate Particle Aerosolization of a Product Under Abrasion and Under Environmental Weathering

The present article presents an experimental protocol to investigate particle aerosolization of a product under abrasion and under environmental weathering, which is a fundamental element to the approach of nanosafety-by-design of nanostructured products for their durable development. This approach is basically a preemptive one in which the focus is put on minimizing the emission of engineered nanomaterials' aerosols during the usage phase of the product's life cycle. This can be attained by altering its material properties during its design phase without compromising with any of its added benefits. In this article, an experimental protocol is presented to investigate the nanosafety-by-design of three commercial nanostructured products with respect to their mechanical solicitation and environmental weathering. The means chosen for applying the mechanical solicitation is an abrasion process and for the environmental weathering, it is an accelerated UV exposure in the presence of humidity and heat. The eventual emission of engineered nanomaterials is studied in terms of their number concentration, size distribution, morphology and chemical composition. The purpose of the protocol is to study the emission for test samples and experimental conditions which are corresponding to real life situations. It was found that the application of the mechanical stresses alone emits the engineered nanomaterials' aerosols in which the engineered nanomaterial is always embedded inside the product matrix, thus, a representative product element. In such a case, the emitted aerosols comprise of both nanoparticles as well as microparticles. But if the mechanical stresses are coupled with the environmental weathering, the experimental protocol reveals then the eventual deterioration of the product, after a certain weathering duration, may lead to the emission of the free engineered nanomaterial aerosols too.

In this article, an experimental protocol to investigate particle aerosolization of a product under abrasion and under environmental weathering is presented. Results on the emission of engineered nanomaterials, in the form of aerosols are presented. The specific experimental set-up is described in detail.

The present article presents an experimental protocol to investigate particle aerosolization of a product under abrasion and under environmental ...

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 ...

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 ...

Scanning Light Scattering Profiler (SLPS) Based Methodology to Quantitatively Evaluate Forward and Backward Light Scattering from Intraocular Lenses

The scanning light scattering profiler (SLSP) methodology has been developed for the full-angle quantitative evaluation of forward and backward light scattering from intraocular lenses (IOLs) using goniophotometer principles. This protocol describes the SLSP platform and how it employs a 360&#176; rotational photodetector sensor that is scanned around an IOL sample while recording the intensity and location of scattered light as it passes through the IOL medium. The SLSP platform can be used to predict, non-clinically, the propensity for current and novel IOL designs and materials to induce light scatter. Non-clinical evaluation of light scattering properties of IOLs can significantly reduce the number of patient complaints related to unwanted glare, glistening, optical defects, poor image quality, and other phenomena associated with the unintended light scattering. Future studies should be conducted to correlate SLSP data with clinical results to help identify which measured light scatter is most problematic for patients that have undergone cataract surgery subsequent to IOL implantation.

Scanning Light Scattering Profiler SLPS Based Methodology to Quantitatively Evaluate Forward and Backward Light Scattering from Intraocular Lenses

This protocol describes the scanning light scattering profiler (SLSP) that enables the full-angle quantitative evaluation of forward and backward scattering of light from intraocular lenses (IOLs) using goniophotometer principles.

The scanning light scattering profiler (SLSP) methodology has been developed for the full-angle quantitative evaluation of forward and backward light ...

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 ...

Indoor Experimental Assessment of the Efficiency and Irradiance Spot of the Achromatic Doublet on Glass (ADG) Fresnel Lens for Concentrating Photovoltaics

We present a method to characterize achromatic Fresnel lenses for photovoltaic applications. The achromatic doublet on glass (ADG) Fresnel lens is composed of two materials, a plastic and an elastomer, whose dispersion characteristics (refractive index variation with wavelength) are different. We first designed the lens geometry and then used ray-tracing simulation, based on the Monte Carlo method, to analyze its performance from the point of view of both optical efficiency and the maximum attainable concentration. Afterwards, ADG Fresnel lens prototypes were manufactured using a simple and reliable method. It consists of a prior injection of plastic parts and a consecutive lamination, together with the elastomer and a glass substrate to fabricate the parquet of ADG Fresnel lenses. The accuracy of the manufactured lens profile is examined using an optical microscope while its optical performance is evaluated using a solar simulator for concentrator photovoltaic systems. The simulator is composed of a xenon flash lamp whose emitted light is reflected by a parabolic mirror. The collimated light has a spectral distribution and an angular aperture similar to the real Sun. We were able to assess the optical performance of the ADG Fresnel lenses by taking photographs of the irradiance spot cast by the lens using a charge-coupled device (CCD) camera and measuring the photocurrent generated by several types of multi junction (MJ) solar cells, which have been previously characterized at a solar simulator for concentrator solar cells. These measurements have demonstrated the achromatic behavior of ADG Fresnel lenses and, as a consequence, the suitability of the modelling and manufacturing methods.

Indoor Experimental Assessment of the Efficiency and Irradiance Spot of the Achromatic Doublet on Glass ADG Fresnel Lens for Concentrating Photovoltaics

The achromatic doublet on glass (ADG) Fresnel lens makes use of two materials with differing dispersion to reduce chromatic aberration and increase attainable concentration. In this paper, a protocol for the complete characterization of the ADG Fresnel lens is presented.