Esta pesquisa foi apoiada como parte do Centro de Energia Nanociência, um Centro de Pesquisa de Energia Frontier financiado pelo Departamento de Energia dos EUA, Escritório de Ciência sob Award Número DE-SC0001013. Queremos também agradecer ao Dr. Max Zhang Jianhua e Dr. Yang do HP Labs por sua ajuda na medição TiO2 pulverização catódica filme e índices de refração.

1. Prepare o polidimetilsiloxano Blank (PDMS) Substrato para nanoimpressão Mold <ol><li> Processo de Tratamento Silicon Wafer <ol><li> Limpar uma bolacha de silício de 4 polegadas por lavagem com acetona, metanol e isopropanol. </li><li> Funda-o secar usando a arma de azoto. </li><li> Limpar com solução piranha (mistura 3: 1 de ácido sulfúrico com 30% de peróxido de hidrogénio) por imersão dentro de 15 min. </li><li> Lavar com água DI. Seque usando a arma de azoto. </li><li> Coloque a bolacha em um dessecador de vidro. Adicionar uma gota (20 gotas = 1 ml) de agente (triclorossilano), libertando no exsicador. </li><li> Pump down exsicador até o medidor lê -762 Torr e esperar por 5 horas. </li><li> Leve o wafer fora, o que tem sido tratada com agente de liberação. </li></ol></li><li> Preparação de PDMS Film (Usado como Mold em nanoimpressão) <ol><li> Pesar 10 g de base de elastómero de silicone e 1 g de agente de cura. </li><li> Adicionar-los na mesma proveta de vidro. </li><li> Stir e misture com uma vareta de vidro durante 5 minutos. </li><li> Coloque a mistura em um exsicador de vácuo até que o calibre lê -762 Torr para bombear para fora todas as bolhas de ar aprisionadas. </li><li> Espalhe-os uniformemente sobre o tratado wafer de silício de 4 polegadas. </li><li> Cozer a bolacha com PDMS em cima no forno de vácuo durante 7 h a 80 ° C para curar o filme de PDMS. </li></ol></li></ol> 2. Prepare o Mold nanoimpressão (Duplicação do Mold Master) <ol><li> Gire doze gotas (20 gotas = 1 ml) de UV curável resistem (15,2%) em um wafer de silício em branco limpo durante 30 segundos a 1500 rpm. </li><li> Retire cuidadosamente um pedaço de filme PDMS fora do wafer de silício tratado. </li><li> Coloque o filme PDMS para o UV curável resistir e deixá-lo absorver a UV resistir por 5 min, em seguida, retire-a. </li><li> Repetir 2,1-2,3 no mesmo filme para PDMS duas vezes. Absorve a resistir UV durante 3 min e 1 min, respectivamente. </li><li> Coloque o filme PDMS (após três vezes UV resistir absorção) sobre um molde mestre de silício. </li><li> Colocá-lo em uma câmara com ambiente de azoto. </li><li> Ligue lâmpada de UV para curar a amostra durante 5 minutos. </li><li> Retire o filme PDMS. O UV curado resistir nas PDMS vai manter o padrão negativo do molde mestre. </li><li> Use RF O2 plasma para tratar o molde PDMS. (Potência RF: 30 W, a pressão: 260 mTorr, tempo: 1 min) </li><li> Coloque o molde PDMS em uma câmara de vácuo com uma gota (20 gotas = 1 ml) do agente de libertação, durante 2 h. </li></ol> 3. nanoimpressão Transferência Padrão <ol><li> Rotação oito gotas (20 gotas = 1 mL) de PMMA (996k, 3,1%) sobre o substrato a ser impresso por 50 segundos a 3500 rpm. </li><li> Asse numa placa de aquecimento durante 5 minutos a 120 ° C. </li><li> Aguarde até que a amostra arrefeça. </li><li> Rotação oito gotas (20 gotas = 1 mL) de UV curável resistem (3,9%) no mesmo substrato. </li><li> Coloque o molde PDMS (preparado no passo 2) para a amostra (com ambos UV resistir e PMMA). </li><li> Colocá-lo em uma câmara com ambiente de azoto.</li><li> Acender a luz UV para curar durante 5 minutos. </li><li> Retire o molde PDMS fora a amostra e o padrão sobre o molde PDMS é transferido para a amostra. </li></ol> 4. Cr Descolagem Processo <ol><li> Ion reativa gravura camada residual de UV resistir e PMMA Nota: A SOP para a máquina ICP pode ser encontrada em https://www.nanocenter.umd.edu/equipment/fablab/sops/etch-07/Oxford%20Chlorine%20Etcher%20SOP.pdf <ol><li> Log in máquina RIE ICP. </li><li> Coloque uma pastilha de silício em branco de 4 polegadas. Executar a receita limpa para 10 min. </li><li> Leve o wafer de silício em branco para fora. </li><li> Monte a amostra em outra pastilha de silício limpo e carregá-lo para dentro da máquina. </li><li> Executar a UV resistir receita condicionamento durante 2 min (a receita pode ser encontrada na Tabela 1). </li><li> Leve a amostra para fora. Coloque uma pastilha de silício em branco de 4 polegadas. Volte a executar a receita limpo (pode ser encontrado na Tabela 1) durante 10 min. </li><li> Monte a amostra sobre uma pastilha de silício limpoe carregá-lo para dentro da máquina. </li><li> Executar a receita gravura PMMA (pode ser encontrada na Tabela 1) durante 2 min. Nota: Agora o resíduo resistem foi gravado e o substrato é exposto. </li></ol></li><li> Cr E-feixe de evaporação <ol><li> Faça o login no evaporador e-feixe. </li><li> Carregue a fonte de metal Cr e amostras para a câmara. </li><li> Defina a espessura (20 nm) e taxa de deposição (0,03 nm / seg). </li><li> Bomba da câmara de vácuo até requerido (10 -7 Torr) é alcançado. </li><li> Iniciar o processo de deposição. </li><li> Leve a amostra para fora após a conclusão de deposição. </li></ol></li><li> Cr Levante-off Procedimento <ol><li> Imergir a amostra em acetona, com agitação ultra-sons durante 5 min. </li><li> Limpar a amostra por lavagem com acetona, metanol e isopropanol. Nota: O Cr evaporada no resistem vai ser retirada e uma máscara de Cr para substrato de gravação é formada. </li></ol></li></ol> 5. TiO 2 DepOSIÇÃO <ol><li> Amostra de carga. </li><li> Defina os parâmetros para a máquina de corrente contínua pulverização catódica <ol><li> Use uma pressão na câmara de 1,5 mTorr, o fluxo de Ar de 100 sccm e uma fonte de pulverização de 130 W. </li><li> Utilize uma temperatura de 27 ° C e uma velocidade de rotação de fase 20 rpm. </li></ol></li><li> Inicie o processo de pulverização catódica e parar em espessura desejada. </li><li> Leve a amostra para fora e emparelhar o TiO 2 filme em ambiente de oxigênio a 300 ° C durante 3 horas. </li></ol> 6. Alto Contraste Grades Gravura <ol><li> Log na máquina de plasma indutivamente acoplado (ICP) gravação iónica reactiva (RIE). </li><li> TiO 2 decapagem <ol><li> Coloque uma pastilha de silício em branco de 4 polegadas. </li><li> Iniciar e executar a receita limpo (pode ser encontrada na Tabela 1) durante 10 min. </li><li> Descarregar carregar o wafer em branco e carregar a amostra com Cr máscara. </li><li> Definir tempo de ataque. Iniciar TiO2 receita decapagem. O processo de gravação vontade automaticamente parar. </li><li> Descarregar a amostra. </li></ol></li><li> SiO2 Etching <ol><li> Repita o passo 5.2 excepto o uso da receita gravura SiO 2. </li></ol></li></ol> Medição 7. Reflectance <ol><li> Fazer login e ligar o sistema de medição. </li><li> Coloque o espelho padrão de reflexão no suporte de amostras e alinhar o caminho óptico. </li><li> Calibrar o sistema para a reflectância a 100%. </li><li> Tire o espelho padrão de reflexão e coloque o HCG. </li><li> Medir a reflectância da HCG. </li><li> Salvar os dados e sair do sistema de medição. </li></ol>

<ol>
	<li>Horne, S., 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=A+Solid+500+Sun+Compound+Concentrator+PV+Design.">A Solid 500 Sun Compound Concentrator PV Design.</a> Photovoltaic Energy Conversion, Conference Record of the 2006 IEEE 4th World Conference on. , 694-697 (2006).</li><li>Guter, W., 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=Current-matched+triple-junction+solar+cell+reaching+41.1%+conversion+efficiency+under+concentrated+sunlight.">Current-matched triple-junction solar cell reaching 41.1% conversion efficiency under concentrated sunlight.</a> Applied Physics Letters. 94, 223504 (2009).</li><li>Shockley, W., Queisser, H. 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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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The authors have nothing to disclose.

Em primeiro lugar, a qualidade do filme de TiO 2 é muito crucial para o desempenho de HCG. O pico de reflectância será mais elevada se o filme de TiO 2 com menos perda e a rugosidade da superfície. O TiO2 filme com um índice de refracção mais elevado, também é favorável porque o modo de confinamento óptica irá ser reforçada por um contraste maior no índice, o que pode dar origem a uma banda mais achatada e mais larga na reflectância HCG. Em seg...

Nossa sociedade moderna não vai sobreviver sem mover uma parcela significativa do consumo de energia de fontes renováveis ​​de energia. Para que isso aconteça, temos de encontrar uma maneira de colher a energia renovável a um custo menor do que as fontes de energia à base de petróleo em um futuro próximo. A energia solar é a energia renovável mais abundante na Terra. Apesar de que um grande número de avanços têm sido feitos na colheita de energia solar, que ainda é muito difícil de competir com fontes de energia à base de petróleo. Melhorar a eficiência das células solares é uma das maneiras mais eficientes para reduzir o custo do sistema de captação de energia solar. Lentes ópticas e reflectores de prato são normalmente utilizados em sistemas fotovoltaicos mais concentrada (CPV) um para alcançar uma elevada concentração de energia solar de incidência sobre as células solares de pequena área, de modo que é economicamente viável para explorar em tandem caro células solares multi-junção em dois sistemas CPV, e para manter um razoávelcustar ao mesmo tempo. No entanto, para a maioria dos sistemas fotovoltaicos não-concentrados, que normalmente exigem uma parcela de células solares de grande área, as células solares em tandem de alto custo não podem ser incorporados, embora eles geralmente têm uma resposta espectro solar mais ampla e uma maior eficiência de conversão global do que o único de junção de células solares 3. Recentemente, com a ajuda dos paralelas óptica de divisão de espectro (isto é, elemento dispersivo), paralela a divisão do espectro tecnologia fotovoltaica 4 tornou possível que uma cobertura de espectro semelhante ou melhor e eficiência de conversão pode ser conseguida sem a utilização de células solares em tandem caro. O espectro solar podem ser divididos em diferentes faixas e cada faixa pode ser absorvida e convertida em electricidade por as células solares de junção única especializados. Desta forma, as células solares em tandem caros nos sistemas CPV pode ser substituído por uma distribuição paralela de uma única junção de células solaress sem qualquer compromisso sobre o desempenho. O elemento de dispersão que foi concebido no presente relatório pode ser aplicada num sistema CPV reflectora (que se baseia na reflectores de prato) para realizar a divisão do espectro paralelo para a melhoria da eficiência de conversão de energia solar de energia elétrica e custo reduzido. Multicamada grelhas de alto contraste (hCG) 5 é utilizado como o elemento de dispersão através da concepção de cada camada de HCG para trabalhar como um reflector de banda óptica. As estruturas e os parâmetros do elemento dispersivo são numericamente optimizado. Além disso, o fabrico de grades de alto contraste para o elemento dispersivo usando dieléctrico (TiO 2) sputtering, nanoimpressão litografia 6 e gravação iónica reactiva é estudada e demonstrada.

<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.

A Figura 1 mostra a implementação do elemento dispersivo (multicamada alta grade contraste (GCH)) num sistema fotovoltaico concentrado. A luz solar é reflectida pelo primeiro espelho primário e colide com o elemento dispersivo reflexiva, em que o feixe é reflectido e dividido em diferentes bandas de comprimentos de onda diferentes. Cada banda vai colidir com um determinado local na matriz de células solares para a melhor absorção e conversão em eletricidade. A chave para este sistema é a conce...

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.

Fabricação de grades de alto contraste para o Splitting Spectrum dispersivo Elemento em um sistema fotovoltaico concentrado

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 visualizações.  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. 

Vídeo: 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 Canalização Contraste de imagem para Rápido III-V heteroepitaxiais Caracterização

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

Engenharia

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 de raios-X de energia dispersiva para 3D Elemental Mapeamento de nanopartículas individuais

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.

Escrevendo redes de Bragg em fibras 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.

Fabricação de Solução totalmente processado inorgânicos nanocristais fotovoltaicos Devices

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.

Recombinação Dynamics em Thin-film materiais fotovoltaicos via Condutividade Microondas resolvida no tempo

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.

Desafios na reológico Caracterização de suspensões altamente concentrado - um estudo de caso para-impressão da tela de prata Cola

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.

Fabricação de alta temperatura de nanoestruturado ria-Stabilized Zirconia-Scaffolds (ZEI) pela<em&gt; In Situ</em&gt; Carbono Templating xerogéis

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.

Detectando a distribuição de cloreto solúvel em água da pasta de cimento em uma maneira de alta precisão

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.

Método para gravação de banda larga de alta resolução espectros de emissão de laboratório arcos relâmpago

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.

Dieletroforese assistida por fluxo: Um método de baixo custo para a fabricação de dispositivos de solução-processable nanofio de alto desempenho

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