Questa ricerca è stata supportata come parte del Centro per l&#39;Energia Nanoscienze, un Frontier Centro di ricerca energetica finanziata dal Dipartimento dell&#39;Energia degli Stati Uniti, Office of Science sotto Premio Numero DE-SC0001013. Vogliamo anche ringraziare il Dr. Max Zhang e il Dr. Jianhua Yang di HP Labs per il loro aiuto su misura TiO 2 sputtering pellicola e indici di rifrazione.

1. Preparare il polidimetilsilossano Blank (PDMS) substrato per nanoimprint Mold <ol><li> Processo Silicon Wafer Trattamento <ol><li> Pulire un wafer di silicio da 4 pollici da risciacquo con acetone, metanolo e isopropanolo. </li><li> Colpo asciugare usando la pistola di azoto. </li><li> Pulire con soluzione Piranha (3: 1 miscela di acido solforico al 30% di perossido di idrogeno) immergendo all&#39;interno per 15 min. </li><li> Risciacquare con acqua deionizzata. Colpo secco utilizzando la pistola di azoto. </li><li> Posizionare il wafer in un essiccatore di vetro. Aggiungere una goccia (20 gocce = 1 ml) di agente (triclorosilano) rilasciando in un essiccatore. </li><li> Pompare giù un essiccatore fino a quando il misuratore legge -762 Torr e attendere 5 ore. </li><li> Prendere wafer out, che è stato trattato con distaccante. </li></ol></li><li> Preparazione di PDMS Film (Utilizzato come Mold in nanoimprint) <ol><li> Pesare 10 g di elastomero siliconico base e 1 g di induritore. </li><li> Aggiungeteli nello stesso bicchiere di vetro. </li><li> StiR e mescolare con una bacchetta di vetro per 5 min. </li><li> Mettere il composto in un essiccatore a vuoto fino a quando il misuratore legge -762 Torr a pompare fuori tutte le bolle d&#39;aria intrappolate. </li><li> Stendere uniformemente sul trattato wafer di silicio da 4 pollici. </li><li> Cuocere la cialda con PDMS sulla parte superiore del forno a vuoto per 7 ore a 80 ° C per trattare la pellicola PDMS. </li></ol></li></ol> 2. Preparare il Mold nanoimprint (duplicazione dal Master Mold) <ol><li> Spin dodici gocce (20 gocce = 1 ml) di UV curable resist (15,2%) su un wafer di silicio pulito vuoto per 30 secondi a 1500 rpm. </li><li> Sbucciare con attenzione un pezzo di pellicola PDMS fuori wafer di silicio trattata. </li><li> Mettere la pellicola PDMS sul UV curabile resistere e lasciare assorbire resistere alla UV per 5 min allora sbucciarla fuori. </li><li> Ripetere 2.1-2.3 sulla stessa pellicola PDMS per due volte. Assorbire resistere UV per 3 minuti e 1 min, rispettivamente. </li><li> Collocare la pellicola PDMS (dopo tre volte UV resistono assorbimento) su uno stampo maestro di silicio. </li><li> Mettetelo in una camera con l&#39;ambiente di azoto. </li><li> Accendere lampada UV per curare il campione per 5 min. </li><li> Staccare la pellicola PDMS. Resistete alla curato UV sui PDMS manterrà il modello negativo dello stampo maestro. </li><li> Usa RF O 2 al plasma per il trattamento stampo PDMS. (Potenza RF: 30 W, pressione: 260 mTorr, tempo: 1 min) </li><li> Collocare lo stampo PDMS in una camera a vuoto con una goccia (20 gocce = 1 ml) di agente di distacco per 2 ore. </li></ol> 3. nanoimprint modello Transfer <ol><li> Spin otto gocce (20 gocce = 1 ml) di PMMA (996k, 3,1%) sul substrato da impresso per 50 secondi a 3.500 giri. </li><li> Cuocere su una piastra per 5 minuti a 120 ° C. </li><li> Attendere che il campione si raffreddi. </li><li> Spin otto gocce (20 gocce = 1 ml) di UV curable resist (3,9%) sullo stesso substrato. </li><li> Mettere lo stampo PDMS (preparata al punto 2) sul campione (sia con UV resistere e PMMA). </li><li> Mettetelo in una camera con l&#39;ambiente di azoto.</li><li> Accendere la lampada UV per curare per 5 min. </li><li> Peel lo stampo PDMS off il campione e il modello sullo stampo PDMS viene trasferito al campione. </li></ol> 4. Cr processo Lift-off <ol><li> Ion etching reattivo strato residuo di UV resistere e PMMA Nota: Il SOP per la macchina ICP sono disponibili all&#39;indirizzo https://www.nanocenter.umd.edu/equipment/fablab/sops/etch-07/Oxford%20Chlorine%20Etcher%20SOP.pdf <ol><li> Entra in macchina RIE ICP. </li><li> Caricare un vuoto wafer di silicio da 4 pollici. Eseguire la ricetta pulita per 10 min. </li><li> Prendete il wafer di silicio vuoto fuori. </li><li> Montare il campione su un altro wafer di silicio pulito e caricarlo nella macchina. </li><li> Eseguire il UV resistono ricetta acquaforte per 2 minuti (la ricetta può essere trovato in Tabella 1). </li><li> Prendere il campione fuori. Caricare un vuoto wafer di silicio da 4 pollici. Eseguire nuovamente la ricetta pulito (si possono trovare nella tabella 1) per 10 minuti. </li><li> Montare il campione su un wafer di silicio pulitoe caricarlo in macchina. </li><li> Eseguire la ricetta acquaforte PMMA (si possono trovare nella tabella 1) per 2 minuti. Nota: Ora la residua resist è stato inciso e substrato è esposto. </li></ol></li><li> Cr E-beam di evaporazione <ol><li> Log in e-beam evaporatore. </li><li> Caricare la sorgente di metallo Cr e del campione nella camera. </li><li> Impostare lo spessore (20 nm) e velocità di deposizione (0,03 nm / sec). </li><li> Pompare la camera fino a vuoto richiesto (10 -7 Torr) è raggiunto. </li><li> Avviare il processo di deposizione. </li><li> Prendere il campione fuori al termine di deposizione. </li></ol></li><li> CR Lift-off Procedura <ol><li> Immergere il campione in acetone con agitazione ad ultrasuoni per 5 min. </li><li> Pulire il campione mediante risciacquo con acetone, metanolo e isopropanolo. Nota: Il Cr evaporato sul resist sarà rimosso e una maschera Cr per substrato attacco è formato. </li></ol></li></ol> 5. TiO2 Deposizione <ol><li> Caricare il campione. </li><li> Impostare i parametri per la macchina diretta magnetron sputtering corrente <ol><li> Utilizzare una pressione della camera di 1,5 mTorr, Ar flusso di 100 sccm e una potenza di 130 W. sputtering </li><li> Utilizzare una temperatura di 27 ° C e una velocità di rotazione di fase 20 rpm. </li></ol></li><li> Avviare il processo di polverizzazione e fermarsi a spessore desiderato. </li><li> Prelevare il campione fuori e ricuocere il film TiO 2 in ambiente di ossigeno a 300 ° C per 3 ore. </li></ol> 6. Forte contrasto stridente Acquaforte <ol><li> Entra nella macchina plasma ad accoppiamento induttivo (ICP) attacco con ioni reattivi (RIE). </li><li> TiO2 acquaforte <ol><li> Caricare un vuoto wafer di silicio da 4 pollici. </li><li> Avviare ed eseguire la ricetta pulito (si possono trovare nella tabella 1) per 10 minuti. </li><li> Scaricare caricare il wafer vuoto e caricare il campione con maschera Cr. </li><li> Imposta tempo di attacco. Inizia TiO2 acquaforte ricetta. La volontà di auto processo di incisioneautomaticamente smettere. </li><li> Scaricare il campione. </li></ol></li><li> SiO 2 Acquaforte <ol><li> Ripetere il punto 5.2 eccezione di usare il SiO 2 acquaforte ricetta. </li></ol></li></ol> 7. riflettanza Misurazione <ol><li> Esegui il login e accendere il sistema di misurazione. </li><li> Posizionare lo specchio campione di riflessione sul portacampioni e allineare il percorso ottico. </li><li> Calibrare il sistema di riflettanza 100%. </li><li> Togliere lo standard specchio di riflessione e posizionare il HCG. </li><li> Misurare la riflettanza della HCG. </li><li> Salvare i dati e uscire dal sistema di misura. </li></ol>

<ol>
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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detailed+Balance+Limit+of+Efficiency+of+p-n+Junction+Solar+Cells.">Detailed Balance Limit of Efficiency of p-n Junction Solar Cells.</a> Journal of Applied Physics. 32, 510-519 (1961).</li><li>Green, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Potential+for+low+dimensional+structures+in+photovoltaics.">Potential for low dimensional structures in photovoltaics.</a> Materials Science and Engineering: B. 74, 118-124 (2000).</li><li>Karagodsky, V., Chang-Hasnain, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physics+of+near-wavelength+high+contrast+gratings.">Physics of near-wavelength high contrast gratings.</a> Opt. Express. 20, 10888-10895 (2012).</li><li>Chou, S. Y., Krauss, P. R., Renstrom, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoimprint+lithography.">Nanoimprint lithography.</a> Journal of Vacuum Science &amp; Technology B: Microelectronics and Nanometer Structures. 14, 4129-4133 (1996).</li><li>Namiki, 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+new+FDTD+algorithm+based+on+alternating-direction+implicit+method.+Microwave+Theory+and+Techniques.">A new FDTD algorithm based on alternating-direction implicit method. Microwave Theory and Techniques.</a> IEEE Transactions on. 47, 2003-2007 (1999).</li><li>Moharam, M. G., Gaylord, T. 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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=Sub-50+nm+period+patterns+with+EUV+interference+lithography.">Sub-50 nm period patterns with EUV interference lithography.</a> Microelectronic Engineering. 67, 56-62 (2003).</li><li>Li, Z., 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=Hybrid+nanoimprint&#8722;+soft+lithography+with+sub-15+nm+resolution.">Hybrid nanoimprint&#8722; soft lithography with sub-15 nm resolution.</a> Nano letters. 9, 2306-2310 (2009).</li><li>Yu, Z., Chen, L., Wu, W., Ge, H., Chou, S. 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The authors have nothing to disclose.

In primo luogo, la qualità del film TiO 2 è molto importante per le prestazioni HCG. Il picco riflettanza sarà maggiore se il film TiO 2 ha meno perdita e rugosità superficiale. Il film TiO 2 con un indice di rifrazione superiore è anche favorevole perché la modalità confinamento ottico sarà arricchito da un elevato contrasto di indice, che può dar luogo ad una più piatta e banda riflettanza più ampia HCG. In secondo luogo, gli errori di fabbricazi...

La nostra società moderna non può sopravvivere senza spostare una parte significativa del consumo di energia alle fonti energetiche rinnovabili. Per ottenere tutto ciò, dobbiamo trovare un modo per raccogliere l&#39;energia rinnovabile ad un costo inferiore rispetto alle fonti energetiche a base di petrolio nel prossimo futuro. L&#39;energia solare è il più abbondante energia rinnovabile sulla terra. Nonostante che molti progressi sono stati fatti nella raccolta di energia solare, è ancora molto difficile competere con le fonti di energia a base di petrolio. Migliorare l&#39;efficienza delle celle solari è uno dei modi più efficaci per abbassare il costo del sistema di raccolta di energia solare. Lenti ottiche e riflettori per i piatti sono di solito utilizzati in fotovoltaici a più alta concentrazione (CPV) sistemi 1 per ottenere una elevata concentrazione di incidenza dell&#39;energia solare sulle celle solari di piccola zona, quindi è economicamente sostenibile per sfruttare tandem costoso multi-giunzione celle solari 2 a sistemi CPV, e per mantenere un ragionevolecostare allo stesso tempo. Tuttavia, per la maggior parte dei sistemi fotovoltaici non concentrati, che di solito richiedono una grande area rata di celle solari, le celle solari tandem ad alto costo non possono essere incorporati, anche se di solito hanno una più ampia risposta spettro solare e una maggiore efficienza di conversione complessiva del celle solari singola giunzione 3. Recentemente, con l&#39;aiuto delle ottiche splitting spettro parallele (cioè dispersivo elemento), la divisione dello spettro tecnologia fotovoltaica parallelo 4 ha permesso che la copertura spettro simile o migliore e l&#39;efficienza di conversione può essere realizzato senza utilizzare le celle solari tandem costoso. Lo spettro solare può essere diviso in diverse bande e ogni banda può essere assorbita e convertita in elettricità dalle celle solari a giunzione specializzati. In questo modo, i tandem costoso celle solari in sistemi CPV possono essere sostituiti da una distribuzione parallela di singola giunzione cella solares, senza alcun compromesso sulla performance. L&#39;elemento dispersivo che è stato progettato in questa relazione può essere applicato in un sistema CPV riflettente (che si basa su riflettori piatto) per realizzare splitting spettro parallelo per il miglioramento solare elettrica efficienza di conversione e costo ridotto. Multistrato grigliati alto contrasto (HCG) 5 viene utilizzato come elemento dispersivo progettando ogni strato di HCG per lavorare come un riflettore banda ottica. Le strutture ei parametri dell&#39;elemento dispersivo sono numericamente ottimizzati. Inoltre, la realizzazione di griglie ad alto contrasto per l&#39;elemento dispersivo utilizzando dielettrico (TiO2) sputtering, nanoimprint litografia 6 e attacco con ioni reattivi si studia e dimostrati.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>184 SILICONE ELASTOMER KIT</td>
			<td>SYLGARD</td>
			<td></td>
			<td>Polydimethylsiloxane (PDMS)</td>
		</tr>
		<tr>
			<td>4-inch silicon wafer</td>
			<td>Universitywafer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>4-inch fused silica wafer</td>
			<td>Universitywafer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Poly(methyl methacrylate)</td>
			<td>SIGMA-ALDRICH</td>
			<td align="right">182265</td>
			<td></td>
		</tr>
		<tr>
			<td>UV-curable resist</td>
			<td></td>
			<td></td>
			<td>Nor available on market</td>
		</tr>
		<tr>
			<td>PlasmaLab System 100</td>
			<td>Oxford Instruments</td>
			<td></td>
			<td>ICP IRE machine</td>
		</tr>
		<tr>
			<td>UV curing system for nanoimprint fabrication</td>
			<td></td>
			<td></td>
			<td>Not available on market</td>
		</tr>
		<tr>
			<td>Ocean Optics HR-4000&#160;</td>
			<td>Ocean Optics</td>
			<td>HR-4000</td>
			<td>Spectrometer with normal detector</td>
		</tr>
		<tr>
			<td>Lambda 950 UV / VIS</td>
			<td>PerkinElmer</td>
			<td></td>
			<td>spectrometer with hemisphere intergration detector</td>
		</tr>
		<tr>
			<td>JSM-7001F-LV</td>
			<td>JEOL</td>
			<td></td>
			<td>Field emission SEM</td>
		</tr>
		<tr>
			<td>DC magnetron sputtering machine</td>
			<td></td>
			<td></td>
			<td>Equipment is in HP labs, who helped us to sputter the TiO2</td>
		</tr>
		<tr>
			<td>Metal e-beam evaporator</td>
			<td>Temescal</td>
			<td>BJD-1800</td>
			<td></td>
		</tr>
	</tbody>
</table>

fabrication of high contrast gratings for the spectrum splitting dispersive element in a concentrated photovoltaic system

High contrast gratings are designed and fabricated and its application is proposed in a parallel spectrum splitting dispersive element that can improve the solar conversion efficiency of a concentrated photovoltaic system. The proposed system will also lower the solar cell cost in the concentrated photovoltaic system by replacing the expensive tandem solar cells with the cost-effective single junction solar cells. The structures and the parameters of high contrast gratings for the dispersive elements were numerically optimized. The large-area fabrication of high contrast gratings was experimentally demonstrated using nanoimprint lithography and dry etching. The quality of grating material and the performance of the fabricated device were both experimentally characterized. By analyzing the measurement results, the possible side effects from the fabrication processes are discussed and several methods that have the potential to improve the fabrication processes are proposed, which can help to increase the optical efficiency of the fabricated devices.

La Figura 1 mostra l&#39;implementazione dell&#39;elemento dispersivo (multistrato alta reticolo contrasto (HCG)) in un impianto fotovoltaico concentrato. La luce del sole viene prima riflessa dallo specchio primario e incide sull&#39;elemento riflettente dispersivo, dove il fascio viene riflesso e diviso in diverse bande di lunghezze d&#39;onda diverse. Ogni banda graverà su una certa posizione sulla matrice di celle solari per il miglior assorbimento e la conversione in energia elettrica. La chiave d...

Watch this Scientific Journal Video about Fabrication of High Contrast Gratings for the Spectrum Splitting Dispersive Element in a Concentrated Photovoltaic System at JoVE.com

Fabrication of High Contrast Gratings for the Spectrum Splitting Dispersive Element in a Concentrated Photovoltaic System

The fabrication of high contrast gratings as the parallel spectrum splitting dispersive element in a concentrated photovoltaic system is demonstrated. Fabrication processes including nanoimprint lithography, TiO2 sputtering and reactive ion etching are described. Reflectance measurement results are used to characterize the optical performance.

Fabbricazione di Grigliati un forte contrasto per la suddivisione Spectrum Dispersive elemento in un sistema fotovoltaico a concentrazione

High contrast gratings are designed and fabricated and its application is proposed in a parallel spectrum splitting dispersive element that can improve ...

fabrication-high-contrast-gratings-for-spectrum-splitting-dispersive

Research

JoVE Journal

Engineering

10.6K Views.  University of Sothern California. The fabrication of high contrast gratings as the parallel spectrum splitting dispersive element in a concentrated photovoltaic system is demonstrated. Fabrication processes including nanoimprint lithography, TiO2 sputtering and reactive ion etching are described. Reflectance measurement results are used to characterize the optical performance. 

Video: Fabrication of High Contrast Gratings for the Spectrum Splitting Dispersive Element in a Concentrated Photovoltaic System

Electron Channeling Contrast Imaging for Rapid III-V Heteroepitaxial Characterization

Misfit dislocations in heteroepitaxial layers of GaP grown on Si(001) substrates are characterized through use of electron channeling contrast imaging (ECCI) in a scanning electron microscope (SEM). ECCI allows for imaging of defects and crystallographic features under specific diffraction conditions, similar to that possible via plan-view transmission electron microscopy (PV-TEM). A particular advantage of the ECCI technique is that it requires little to no sample preparation, and indeed can use large area, as-produced samples, making it a considerably higher throughput characterization method than TEM. Similar to TEM, different diffraction conditions can be obtained with ECCI by tilting and rotating the sample in the SEM. This capability enables the selective imaging of specific defects, such as misfit dislocations at the GaP/Si interface, with high contrast levels, which are determined by the standard invisibility criteria. An example application of this technique is described wherein ECCI imaging is used to determine the critical thickness for dislocation nucleation for GaP-on-Si by imaging a range of samples with various GaP epilayer thicknesses. Examples of ECCI micrographs of additional defect types, including threading dislocations and a stacking fault, are provided as demonstration of its broad, TEM-like applicability. Ultimately, the combination of TEM-like capabilities &#8211; high spatial resolution and richness of microstructural data &#8211; with the convenience and speed of SEM, position ECCI as a powerful tool for the rapid characterization of crystalline materials.

The use of electron channeling contrast imaging in a scanning electron microscope to characterize defects in III-V/Si heteroexpitaxial thin films is described. This method yields similar results to plan-view transmission electron microscopy, but in significantly less time due to lack of required sample preparation.

Electron Channeling Contrast Imaging per Rapid III-V eteroepitassiale Caratterizzazione

Misfit dislocations in heteroepitaxial layers of GaP grown on Si(001) substrates are characterized through use of electron channeling contrast imaging ...

Ricerca

Ingegneria

Energy Dispersive X-ray Tomography for 3D Elemental Mapping of Individual Nanoparticles

Energy dispersive X-ray spectroscopy within the scanning transmission electron microscope (STEM) provides accurate elemental analysis with high spatial resolution, and is even capable of providing atomically resolved elemental maps. In this technique, a highly focused electron beam is incident upon a thin sample and the energy of emitted X-rays is measured in order to determine the atomic species of material within the beam path. This elementally sensitive spectroscopy technique can be extended to three dimensional tomographic imaging by acquiring multiple spectrum images with the sample tilted along an axis perpendicular to the electron beam direction.
Elemental distributions within single nanoparticles are often important for determining their optical, catalytic and magnetic properties. Techniques such as X-ray tomography and slice and view energy dispersive X-ray mapping in the scanning electron microscope provide elementally sensitive three dimensional imaging but are typically limited to spatial resolutions of &gt; 20 nm. Atom probe tomography provides near atomic resolution but preparing nanoparticle samples for atom probe analysis is often challenging. Thus, elementally sensitive techniques applied within the scanning transmission electron microscope are uniquely placed to study elemental distributions within nanoparticles of dimensions 10-100 nm.
Here, energy dispersive X-ray (EDX) spectroscopy within the STEM is applied to investigate the distribution of elements in single AgAu nanoparticles. The surface segregation of both Ag and Au, at different nanoparticle compositions, has been observed.

The use of energy dispersive X-ray tomography in the scanning transmission electron microscope to characterize elemental distributions within single nanoparticles in three dimensions is described.

Tomografia a dispersione di energia dei raggi X per il 3D Elemental mappatura delle nanoparticelle individuali

Energy dispersive X-ray spectroscopy within the scanning transmission electron microscope (STEM) provides accurate elemental analysis with high spatial ...

Writing Bragg Gratings in Multicore Fibers

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong suppression at a single wavelength requires that all cores have matching transmission profiles. These gratings cannot be inscribed using the same method as for single-core fibers because the curved surface of the cladding acts as a lens, focusing the incoming UV laser beam and causing variations in exposure between cores. Therefore we use an additional optical element to ensure that the beam shape does not change while passing through the cross-section of the multicore fiber. This consists of a glass capillary tube which has been polished flat on one side, which is then placed over the section of the fiber to be inscribed. The laser beam enters the fiber through the flat surface of the capillary tube and hence maintains its original dimensions. This paper demonstrates the improvements in core-to-core uniformity for a 7-core fiber using this method. The technique can be generalized to larger multicore fibers.

We describe a technique for inscribing identical fiber Bragg gratings into each core of a multicore fiber. This is achieved by introducing an additional surface into the optical path to mitigate lensing by the curved surface of the fiber cladding.

Scrivendo di Bragg in fibra Multicore

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong ...

Fabrication of Fully Solution Processed Inorganic Nanocrystal Photovoltaic Devices

We demonstrate a method for the preparation of fully solution processed inorganic solar cells from a spin and spray coating deposition of nanocrystal inks. For the photoactive absorber layer, colloidal CdTe and CdSe nanocrystals (3-5 nm) are synthesized using an inert hot injection technique and cleaned with precipitations to remove excess starting reagents. Similarly, gold nanocrystals (3-5 nm) are synthesized under ambient conditions and dissolved in organic solvents. In addition, precursor solutions for transparent conductive indium tin oxide (ITO) films are prepared from solutions of indium and tin salts paired with a reactive oxidizer. Layer-by-layer, these solutions are deposited onto a glass substrate following annealing (200-400 &#176;C) to build the nanocrystal solar cell (glass/ITO/CdSe/CdTe/Au). Pre-annealing ligand exchange is required for CdSe and CdTe nanocrystals where films are dipped in NH4Cl:methanol to replace long-chain native ligands with small inorganic Cl- anions. NH4Cl(s) was found to act as a catalyst for the sintering reaction (as a non-toxic alternative to the conventional CdCl2(s) treatment) leading to grain growth (136&#177;39 nm) during heating. The thickness and roughness of the prepared films are characterized with SEM and optical profilometry. FTIR is used to determine the degree of ligand exchange prior to sintering, and XRD is used to verify the crystallinity and phase of each material. UV/Vis spectra show high visible light transmission through the ITO layer and a red shift in the absorbance of the cadmium chalcogenide nanocrystals after thermal annealing. Current-voltage curves of completed devices are measured under simulated one sun illumination. Small differences in deposition techniques and reagents employed during ligand exchange have been shown to have a profound influence on the device properties. Here, we examine the effects of chemical (sintering and ligand exchange agents) and physical treatments (solution concentration, spray-pressure, annealing time and annealing temperature) on photovoltaic device performance.

This protocol describes the synthesis and solution deposition of inorganic nanocrystals layer by layer to produce thin film electronics on non-conductive surfaces. Solvent-stabilized inks can produce complete photovoltaic devices on glass substrates via spin and spray coating following post-deposition ligand exchange and sintering.

Fabbricazione di inorganici nanocristalli fotovoltaici dispositivi completamente Soluzione Processing

We demonstrate a method for the preparation of fully solution processed inorganic solar cells from a spin and spray coating deposition of nanocrystal ...

Recombination Dynamics in Thin-film Photovoltaic Materials via Time-resolved Microwave Conductivity

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials such as organo-lead halide perovskites is presented. The perovskite film thickness and absorption coefficient are initially characterized by profilometry and UV-VIS absorption spectroscopy. Calibration of both laser power and cavity sensitivity is described in detail. A protocol for performing Flash-photolysis Time Resolved Microwave Conductivity (TRMC) experiments, a non-contact method of determining the conductivity of a material, is presented. A process for identifying the real and imaginary components of the complex conductivity by performing TRMC as a function of microwave frequency is given. Charge carrier dynamics are determined under different excitation regimes (including both power and wavelength). Techniques for distinguishing between direct and trap-mediated decay processes are presented and discussed. Results are modelled and interpreted with reference to a general kinetic model of photoinduced charge carriers in a semiconductor. The techniques described are applicable to a wide range of optoelectronic materials, including organic and inorganic photovoltaic materials, nanoparticles, and conducting/semiconducting thin films.

A Time Resolved Microwave Conductivity technique for investigating direct and trap-mediated recombination dynamics and determining carrier mobilities of thin film semiconductors is presented here.

La ricombinazione Dynamics nel fotovoltaici a film sottile Materiali tramite risolta nel tempo Microonde Conducibilità

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials ...

Challenges in Rheological Characterization of Highly Concentrated Suspensions &#8212; A Case Study for Screen-printing Silver Pastes

A comprehensive rheological characterization of highly concentrated suspensions or pastes is mandatory for a targeted product development meeting the manifold requirements during processing and application of such complex fluids. In this investigation, measuring protocols for a conclusive assessment of different process relevant rheological parameters have been evaluated. This includes the determination of yield stress, viscosity, wall slip velocity, structural recovery after large deformation and elongation at break as well as tensile force during filament stretching.
The importance of concomitant video recordings during parallel-plate rotational rheometry for a significant determination of rheological quantities is demonstrated. The deformation profile and flow field at the sample edge can be determined using appropriate markers. Thus, measurement parameter settings and plate roughness values can be identified for which yield stress and viscosity measurements are possible. Slip velocity can be measured directly and measuring conditions at which plug flow, shear banding or sample spillover occur can be identified clearly. 
Video recordings further confirm that the change in shear moduli observed during three stage oscillatory shear tests with small deformation amplitude in stage I and III but large oscillation amplitude in stage II can be directly attributed to structural break down and recovery. For the pastes investigated here, the degree of irreversible, shear-induced structural change increases with increasing deformation amplitude in stage II until a saturation is reached at deformations corresponding to the crossover of G' and G'', but the irreversible damage is independent of the duration of large amplitude shear. 
A capillary breakup elongational rheometer and a tensile tester have been used to characterize deformation and breakup behavior of highly filled pastes in uniaxial elongation. Significant differences were observed in all experiments described above for two commercial screen-printing silver pastes used for front side metallization of Si-solar cells.

Challenges in Rheological Characterization of Highly Concentrated Suspensions &amp;#8212; A Case Study for Screen-printing Silver Pastes

A protocol for a robust and application relevant rheological characterization of highly concentrated suspensions is presented. Silver pastes used for screen-printing application in solar cell production are employed as model systems.

Le sfide in reologico Caratterizzazione di sospensioni altamente concentrato - un caso di studio per la serigrafia paste d&#39;argento

A comprehensive rheological characterization of highly concentrated suspensions or pastes is mandatory for a targeted product development meeting the ...

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) scaffolds with tunable specific surface areas up to 80 m2&#183;g-1. An aqueous solution of a zirconium salt, yttrium salt, and glucose is mixed with propylene oxide (PO) to form a gel. The gel is dried under ambient conditions to form a xerogel. The xerogel is pressed into pellets and then sintered in an argon atmosphere. During sintering, a YSZ ceramic phase forms and the organic components decompose, leaving behind amorphous carbon. The carbon formed in situ serves as a hard template, preserving a high surface area YSZ nanomorphology at sintering temperature. The carbon is subsequently removed by oxidation in air at low temperature, resulting in a porous, nanostructured YSZ scaffold. The concentration of the carbon template and the final scaffold surface area can be systematically tuned by varying the glucose concentration in the gel synthesis. The carbon template concentration was quantified using thermogravimetric analysis (TGA), the surface area and pore size distribution was determined by physical adsorption measurements, and the morphology was characterized using scanning electron microscopy (SEM). Phase purity and crystallite size was determined using X-ray diffraction (XRD). This fabrication approach provides a novel, flexible platform for realizing unprecedented scaffold surface areas and nanomorphologies for ceramic-based electrochemical energy conversion applications, e.g. solid oxide fuel cell (SOFC) electrodes.

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels

A protocol for fabricating porous, nanostructured yttria-stabilized-zirconia (YSZ) scaffolds at temperatures between 1,000 &#176;C and 1,400 &#176;C is presented.

Fabbricazione ad alta temperatura di Nanostrutturati di ossido di ittrio stabilizzato-Zirconia (YSZ) Ponteggi da<em&gt; In Situ</em&gt; Carbon Templating xerogel

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) ...

Detecting the Water-soluble Chloride Distribution of Cement Paste in a High-precision Way

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a high-precision chloride profile. Firstly, paste specimens are molded, cured, and exposed to cyclic wet-dry conditions. Then, powder samples at different specimen depths are grinded when the exposure age is reached. Finally, the water-soluble chloride content is detected using a silver nitrate titration method, and chloride profiles are plotted. The key to improving the accuracy of the chloride distribution along the depth is to exclude the error in the powderization, which is the most critical step for testing the distribution of chloride. Based on the above concept, the grinding method in this protocol can be used to grind powder samples automatically layer by layer from the surface inward, and it should be noted that a very thin grinding thickness (less than 0.5 mm) with a minimum error less than 0.04 mm can be obtained. The chloride profile obtained by this method better reflects the chloride distribution in specimens, which helps researchers to capture the distribution features that are often overlooked. Furthermore, this method can be applied to studies in the field of cement-based materials, which require high chloride distribution accuracy.

A protocol for obtaining a water-soluble chloride profile by using a high precision milling method is presented.

Rilevare la distribuzione di cloruro solubile in acqua della pasta di cemento in un modo ad alta precisione

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a ...

Method for Recording Broadband High Resolution Emission Spectra of Laboratory Lightning Arcs

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional camera film methods and then digital camera technology, from which several important characteristics have been derived. However, such work has always been limited due to the inherently random and non-repeatable nature of natural lightning events in the field. Recent developments in lightning test facilities now allow the reproducible generation of lightning arcs within controlled laboratory environments, providing a test bed for the development of new sensors and diagnostic techniques to understand lightning mechanisms better. One such technique is a spectroscopic system using digital camera technology capable of identifying the chemical elements with which the lightning arc interacts, with these data then being used to derive further characteristics. In this paper, the spectroscopic system is used to obtain the emission spectrum from a 100 kA peak, 100 &#181;s duration lightning arc generated across a pair of hemispherical tungsten electrodes separated by a small air gap. To maintain a spectral resolution of less than 1 nm, several individual spectra were recorded across discrete wavelength ranges, averaged, stitched, and corrected to produce a final composite spectrum in the 450 nm (blue light) to 890 nm (near infrared light) range. Characteristic peaks within the data were then compared to an established publicly available database to identify the chemical element interactions. This method is readily applicable to a variety of other light emitting events, such as fast electrical discharges, partial discharges, and sparking in electrical equipment, apparatus, and systems.

Emission spectroscopy techniques have traditionally been used to analyze inherently random lightning arcs occurring in nature. In this paper, a method developed to obtain the emission spectroscopy from reproducible lightning arcs generated within a laboratory environment is described.

Metodo per la registrazione dei spettri ad alta risoluzione a banda larga degli arci fulmini di laboratorio

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional ...

Flow-assisted Dielectrophoresis: A Low Cost Method for the Fabrication of High Performance Solution-processable Nanowire Devices

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of nanowires. DEP is used for nanowire analysis, characterization, and for solution-based fabrication of semiconducting devices. The method works by applying an alternating electric field between metallic electrodes. The nanowire formulation is then dropped onto the electrodes which are on an inclined surface to create a flow of the formulation using gravity. The nanowires then align along the gradient of the electric field and in the direction of the liquid flow. The frequency of the field can be adjusted to select nanowires with superior conductivity and lower trap density. 
In this work, flow-assisted DEP is used to create nanowire field effect transistors. Flow-assisted DEP has several advantages: it allows selection of nanowire electrical properties; control of nanowire length; placement of nanowires in specific areas; control of orientation of nanowires; and control of nanowire density in the device. 
The technique can be expanded to many other applications such as gas sensors and microwave switches. The technique is efficient, quick, reproducible, and it uses a minimal amount of dilute solution making it ideal for the testing of novel nanomaterials. Wafer scale assembly of nanowire devices can also be achieved using this technique, allowing large numbers of samples for testing and large-area electronic applications.

In this paper, flow assisted dielectrophoresis is demonstrated for the self-assembly of nanowire devices. The fabrication of a silicon nanowire field effect transistor is shown as an example.

Flusso-assistita dielettroforesi: Un metodo a basso costo per la realizzazione di dispositivi ad alte prestazioni soluzione-processable Nanowire

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of ...