The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Miro Zeman - One of the best experts on this subject based on the ideXlab platform.
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experimental demonstration of 4n2 classical absorption limit in nanotextured ultrathin solar cells with dielectric omnidirectional Back Reflector
ACS Photonics, 2014Co-Authors: Andrea Ingenito, Olindo Isabella, Miro ZemanAbstract:The experimental demonstration of the 4n2 classical absorption limit in solar cells has been elusive for the last 30 years. Especially the assumptions on front and internal rear reflectance in a slab of absorbing material are not easily fulfilled unless an appropriate light-trapping scheme is applied. We propose an advanced metal-free light-trapping scheme for crystalline silicon wafers. For different bulk thicknesses, at the front side of the wafers we applied a nanotexture known as black-silicon. At the rear side, we implemented a random pyramidal texture coated with a distributed Bragg Reflector. Such a dielectric Back Reflector was designed to exhibit a maximized omnidirectional internal rear reflectance in the region of weak absorption of crystalline silicon. Integrating the measured absorptance spectra of our wafers with the reference solar photon flux between 400 and 1200 nm, we could calculate the so-called implied photogenerated current densities. For wafers thinner than 35 μm, we achieved more t...
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combined optical and electrical design of plasmonic Back Reflector for high efficiency thin film silicon solar cells
Photovoltaic Specialists Conference, 2013Co-Authors: Hairen Tan, Arno H. M. Smets, Rudi Santbergen, Guangtao Yang, Miro ZemanAbstract:A Back Reflector (BR) that can efficiently scatter weakly absorbed light is essential to obtain high-efficiency thin-film silicon solar cells. We present the design routes of plasmonic BR based on self-assembled silver nanoparticles (Ag NPs) for high-efficiency thin-film silicon solar cells. Both optical and electrical effects on solar cells are considered. The shape of Ag NPs, the thickness of ZnO:Al spacer layers,materials on top of Ag NPs, and nanoparticle size are crucial for the performance of plasmonic BR. Increased annealing temperature lead to the formation of more appropriate shapes (more spherical and regular shapes) for a good light scattering and, thus, increase the photocurrent. The ZnO:Al layer between the Ag NPs and the Ag planar film has an optical effect on solar cells, while the ZnO:Al layer between the Ag NPs and the doped a-Si:H has both optical and electrical influence on the device. Larger NPs have less parasitic absorption and can preferentially scatter light into larger angles, thus increasing the spectral response in the solar cell. However, for larger Ag NPs, the fill factor deteriorates due to the rougher surface in the plasmonic BR, indicating a compromise between light trapping and electrical performance. Following the design routes, we obtained 8.4% high-efficiency plasmonic a-Si:H solar cell.
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improved light trapping in microcrystalline silicon solar cells by plasmonic Back Reflector with broad angular scattering and low parasitic absorption
Applied Physics Letters, 2013Co-Authors: Hairen Tan, Rudi Santbergen, Miro Zeman, Baojie Yan, Laura Sivec, Arno H. M. SmetsAbstract:We show experimentally that the photocurrent of thin-film hydrogenated microcrystalline silicon (μc-Si:H) solar cells can be enhanced by 4.5 mA/cm2 with a plasmonic Back Reflector (BR). The light trapping performance is improved using plasmonic BR with broader angular scattering and lower parasitic absorption loss through tuning the size of silver nanoparticles. The μc-Si:H solar cells deposited on the improved plasmonic BR demonstrate a high photocurrent of 26.3 mA/cm2 which is comparable to the state-of-the-art textured Ag/ZnO BR. The commonly observed deterioration of fill factor is avoided by using μc-SiOx:H as the n-layer for solar cells deposited on plasmonic BR.
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The role of oxide interlayers in Back Reflector configurations for amorphous silicon solar cells
Journal of Applied Physics, 2013Co-Authors: Valeria Demontis, Arno H. M. Smets, Rudi Santbergen, Carla Sanna, Jimmy Melskens, Alfonso Damiano, Miro ZemanAbstract:Thin oxide interlayers are commonly added to the Back Reflector of thin-film silicon solar cells to increase their current. To gain more insight in the enhancement mechanism, we tested different Back Reflector designs consisting of aluminium-doped zinc oxide (ZnO:Al) and/or hydrogenated silicon oxide (SiOx:H) interlayers with different metals (silver, aluminium, and chromium) in standard p-i-n a-Si:H solar cells. We use a unique inverse modeling approach to show that in most Back Reflectors the internal metal reflectance is lower than expected theoretically. However, the metal reflectance is increased by the addition of an oxide interlayer. Our experiments demonstrate that SiOx:H forms an interesting alternative interlayer because unlike the more commonly used ZnO:Al it can be deposited by plasma-enhanced chemical vapour deposition and it does not reduce the fill factor. The largest efficiency enhancement is obtained with a double interlayer of SiOx:H and ZnO:Al.
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Towards Lambertian internal light scattering in solar cells using coupled plasmonic and dielectric nanoparticles as Back Reflector
Conference Record of the IEEE Photovoltaic Specialists Conference, 2013Co-Authors: Rudi Santbergen, Johan Blanker, Aditya Dhathathreyan, Hairen Tan, Arno H. M. Smets, Miro ZemanAbstract:We present a novel approach that opens the route to exceeding the 4n2 light trapping limit. White paint, usually based on titanium dioxide (TiO2) nanoparticles, is well known for its high reflectance and excellent light scattering properties. The angular intensity distribution (AID) is close to the ideal Lambertian cos(φ) distribution when light is scattered into air. White paint therefore seems to be the ideal Back Reflector for solar cell applications. However, when white paint scatters light into c-Si, the AID is refracted into a narrower cone, leading to a large deviation from the Lambertian scattering. Here we present an effective approach to avoid this refraction effect and significantly improve light trapping. Our approach is based on combining dielectric TiO2 nanoparticles with plasmonic silver nanoparticles. The dielectric particles efficiently couple the incident light to the plasmonic particles which in turn couple the light into the absorber layer. Because plasmonic nanoparticles can couple the light beyond the critical angle, the resulting AID inside the absorber is much broader than without the plasmonic particles. We show that this leads to improved light trapping and solar cell performance.
Christophe Ballif - One of the best experts on this subject based on the ideXlab platform.
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silver versus white sheet as a Back Reflector for microcrystalline silicon solar cells deposited on lpcvd zno electrodes of various textures
Progress in Photovoltaics, 2015Co-Authors: Rami Khazaka, Franz-josef Haug, Etienne Moulin, Mathieu Boccard, Loic Garcia, Simon Hanni, F Meillaud, Christophe BallifAbstract:We compare the performance of two Back Reflector designs on the optoelectrical properties of microcrystalline silicon solar cells. The first one consists of a 5-mu m-thick low-pressure chemical vapor deposition (LPCVD)-ZnO electrode combined with a white sheet; the second one incorporates an Ag Reflector deposited on a thin LPCVD-ZnO layer (with thickness below 200nm). For this latter design, the optical loss in the nano-rough Ag Reflector can be strongly reduced by smoothing the surface of the thin underlying ZnO layer, by means of an Ar-plasma treatment. Because of its superior lateral conductivity, the thin-ZnO/Ag Back Reflector design provides a higher fill factor than the dielectric Back Reflector design. When decreasing the roughness of the front electrode with respect to our standard front LPCVD-ZnO layer, the electrical cell performance is improved; in addition, the implementation of the thin-ZnO/Ag Back Reflector leads to a significant relative gain in light trapping. Applying this newly optimized combination of front and Back electrodes, the conversion efficiency is improved from 8.9% up to 9.4%, for cells with an active-layer thickness of only 1.1 mu m. We thereby highlight the necessity to optimize simultaneously the front and Back electrodes. Copyright (c) 2014 John Wiley & Sons, Ltd.
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High-Efficiency Amorphous Silicon Solar Cell on a Periodic Nanocone Back Reflector
Advanced Energy Materials, 2012Co-Authors: Ching-mei Hsu, Celine Pahud, Franz-josef Haug, Zhichao Ruan, Corsin Battaglia, Christophe Ballif, Shanhui Fan, Yi CuiAbstract:An amorphous silicon solar cell on a periodic nanocone Back Reflector with a high 9.7% initial conversion efficiency is presented. The optimized Back-Reflector morphology provides powerful light trapping and enables excellent electrical cell performance. Up-scaling to industrial production of large-area modules should be possible using nanoimprint lithography.
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highly reflective nanotextured sputtered silver Back Reflector for flexible high efficiency n i p thin film silicon solar cells
Solar Energy Materials and Solar Cells, 2011Co-Authors: Karin Soderstrom, Celine Pahud, Franz-josef Haug, Jordi Escarre, Remi Biron, Christophe BallifAbstract:High reflectivity is essential when a metal is used as Back contact and Reflector in thin-film silicon solar cells. We show that thermal annealing at 150 °C improves the reflectivity of silver films deposited by sputtering at room temperature on nanotextured substrates. The annealing provokes two interlinked effects: rearrangement of the silver layer with a modification of its morphology and an increase of up to 42% in the grain size of the polycrystalline film for the preferential orientation as measured by X-ray diffraction. The main consequence of these two mechanisms is a large increase in the reflectivity of silver when measured in air. This reflectivity increase is also noticeable in devices: amorphous silicon thin-film solar cells grown on annealed silver films yield higher internal and external quantum efficiencies compared to cells grown on as-deposited silver. The morphology modification smoothes down the substrate, which is revealed by a clear increase of the open-circuit voltage and fill factor of the cells grown on top. An amorphous silicon cell with a 200 nm nominally thick i-layer fabricated on a flexible plastic substrate yielded an initial efficiency close to 10% with 15.9 mA/cmof short-circuit current using highly reflective annealed textured silver. We also propose, for industrial purpose, the sputtering of thin silver layer (120 nm) under moderate substrate temperature (∼150 °C) to increase the layer reflectivity, which avoids lengthening of the Back Reflector fabrication.
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transmission electron microscopy of the textured silver Back Reflector of a thin film silicon solar cell from crystallography to optical absorption
World Conference on Photovoltaic Energy Conversion, 2011Co-Authors: Rafal E Duninborkowski, Christophe Ballif, F J Haug, Takeshi Kasama, C B Boothroyd, Quentin Jeangros, Karin Soderstrom, Martial DuchampAbstract:The study of light trapping in amorphous, microcrystalline and micromorph thin-film Si solar cells is an important and active field of investigation. It has been demonstrated that the use of a rough Ag Back-Reflector lead to an increase of short circuit current but also to losses through the creation of surface plasmon polaritons. Here, we use transmission electron microscopy (TEM) techniques to study the grain structure of a Ag thin-film that was sputtered on top of 2-μm-thick rough ZnO layer defects, such as twin-boundaries have been observed. A smoothing of the top Ag surface was also observed after ex-situ annealing. Electron energy-loss spectroscopy with a monochromatic beam was used to measure the surface plasmon resonance with nm spatial resolution. 1 eV and 3 eV Ag surface plasmon resonances have been observed on as-grown layers. Such measurements provide valuable information about the origin of optical absorption losses previously measured in Ag Back-Reflector of thin-film Si solar cells.
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photocurrent enhancement in thin film amorphous silicon solar cells with silver nanoparticles
Progress in Photovoltaics, 2011Co-Authors: C Eminian, F J Haug, O Cubero, X Niquille, Christophe BallifAbstract:Silver nanoparticles embedded in a dielectric material have strong scattering properties under light illumination, due to localized surface plasmons. This effect is a potential way to achieve light trapping in thin-film solar cells. In this paper we study light scattering properties of nanoparticles on glass and ZnO, and on silver coated with ZnO, which represent the Back Reflector of a solar cell. We find that large nanoparticles embedded in the dielectric at the Back contact of amorphous silicon solar cells lead to a remarkable increase in short circuit current of 20% compared to co-deposited cells without nanoparticles. This increase is strongly correlated with the enhanced cell absorption in the long wavelengths and is attributed to localized surface plasmons. We also discuss the electrical properties of the cells. Copyright # 2010 John Wiley & Sons, Ltd.
Lionel C. Kimerling - One of the best experts on this subject based on the ideXlab platform.
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demonstration of enhanced absorption in thin film si solar cells with textured photonic crystal Back Reflector
Applied Physics Letters, 2008Co-Authors: Lingping Zeng, B. A. Alamariu, X. Duan, C Hong, Jifeng Liu, Peter Bermel, Kurt Broderick, John D Joannopoulos, Lionel C. KimerlingAbstract:Herein the authors report the experimental application of a powerful light trapping scheme, the textured photonic crystal (TPC) Backside Reflector, to thin film Si solar cells. TPC combines a one-dimensional photonic crystal as a distributed Bragg Reflector with a diffraction grating. Light absorption is strongly enhanced by high reflectivity and large angle diffraction, as designed with scattering matrix analysis. 5 μm thick monocrystalline thin film Si solar cells integrated with TPC were fabricated through an active layer transfer technique. Measured short circuit current density Jsc was increased by 19%, compared to a theoretical prediction of 28%.
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Efficiency enhancement in Si solar cells by textured photonic crystal Back Reflector
Applied Physics Letters, 2006Co-Authors: L. Zeng, X. Duan, Y. Yi, C Hong, Ningjun Feng, Lionel C. Kimerling, B. A. AlamariuAbstract:An efficient light-trapping scheme is developed for solar cells that\ncan enhance the optical path length by several orders of magnitude\nusing a textured photonic crystal as a Backside Reflector. It comprises\na reflection grating etched on the Backside of the substrate and\na one-dimensional photonic crystal deposited on the grating. Top-contacted\ncrystalline Si solar cells integrated with the textured photonic\ncrystal Back Reflector were designed and fabricated. External quantum\nefficiency was significantly improved between the wavelengths of\n1000 and 1200 nm (enhancement up to 135 times), and the overall power\nconversion efficiency was considerably increased.
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new solar cells with novel light trapping via textured photonic crystal Back Reflector
MRS Proceedings, 2005Co-Authors: L. Zeng, B. A. Alamariu, X. Duan, C Hong, Jifeng Liu, Lionel C. KimerlingAbstract:We have successfully developed a new light-trapping scheme for solar cells that can enhance the optical path length by more than 104 times using a textured photonic crystal structure as a Backside Reflector. Top-contacted crystalline Si solar cells integrated with the new Back Reflector were designed, fabricated and characterized. Both external quantum efficiency and power conversion efficiency of the cells have shown significant improvement due to the path length enhancement furnished by the new Back Reflector despite of the 675 um thick wafers and relatively short minority carrier diffusion length.
B. A. Alamariu - One of the best experts on this subject based on the ideXlab platform.
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enhanced absorption in thin film si solar cells with textured photonic Back Reflector
Conference on Lasers and Electro-Optics, 2010Co-Authors: K A Broderick, B. A. Alamariu, X. Duan, L. Zeng, Z Zou, Jian Zhou, X SunAbstract:we present the design, processing and characterization of Si-on-insulator thin film solar cells integrated with textured photonic Backside Reflector. A processing method was successfully developed to integrate the photonic structure to SOI solar cells. Cells at all thicknesses demonstrated significant external quantum efficiency (EQE) enhancement due to the Back Reflector.
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demonstration of enhanced absorption in thin film si solar cells with textured photonic crystal Back Reflector
Applied Physics Letters, 2008Co-Authors: Lingping Zeng, B. A. Alamariu, X. Duan, C Hong, Jifeng Liu, Peter Bermel, Kurt Broderick, John D Joannopoulos, Lionel C. KimerlingAbstract:Herein the authors report the experimental application of a powerful light trapping scheme, the textured photonic crystal (TPC) Backside Reflector, to thin film Si solar cells. TPC combines a one-dimensional photonic crystal as a distributed Bragg Reflector with a diffraction grating. Light absorption is strongly enhanced by high reflectivity and large angle diffraction, as designed with scattering matrix analysis. 5 μm thick monocrystalline thin film Si solar cells integrated with TPC were fabricated through an active layer transfer technique. Measured short circuit current density Jsc was increased by 19%, compared to a theoretical prediction of 28%.
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Efficiency enhancement in Si solar cells by textured photonic crystal Back Reflector
Applied Physics Letters, 2006Co-Authors: L. Zeng, X. Duan, Y. Yi, C Hong, Ningjun Feng, Lionel C. Kimerling, B. A. AlamariuAbstract:An efficient light-trapping scheme is developed for solar cells that\ncan enhance the optical path length by several orders of magnitude\nusing a textured photonic crystal as a Backside Reflector. It comprises\na reflection grating etched on the Backside of the substrate and\na one-dimensional photonic crystal deposited on the grating. Top-contacted\ncrystalline Si solar cells integrated with the textured photonic\ncrystal Back Reflector were designed and fabricated. External quantum\nefficiency was significantly improved between the wavelengths of\n1000 and 1200 nm (enhancement up to 135 times), and the overall power\nconversion efficiency was considerably increased.
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new solar cells with novel light trapping via textured photonic crystal Back Reflector
MRS Proceedings, 2005Co-Authors: L. Zeng, B. A. Alamariu, X. Duan, C Hong, Jifeng Liu, Lionel C. KimerlingAbstract:We have successfully developed a new light-trapping scheme for solar cells that can enhance the optical path length by more than 104 times using a textured photonic crystal structure as a Backside Reflector. Top-contacted crystalline Si solar cells integrated with the new Back Reflector were designed, fabricated and characterized. Both external quantum efficiency and power conversion efficiency of the cells have shown significant improvement due to the path length enhancement furnished by the new Back Reflector despite of the 675 um thick wafers and relatively short minority carrier diffusion length.
Ounsi El Daif - One of the best experts on this subject based on the ideXlab platform.
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broadband absorption enhancement in ultra thin crystalline si solar cells by incorporating metallic and dielectric nanostructures in the Back Reflector
Progress in Photovoltaics, 2015Co-Authors: S C Jain, Valerie Depauw, Vladimir D Miljkovic, Alexandre Dmitriev, Christos Trompoukis, Ivan Gordon, Pol Van Dorpe, Ounsi El DaifAbstract:We propose a Back reflecting scheme in order to enhance the maximum achievable current in one micron thick crystalline silicon solar cells. We perform 3D numerical investigations of the scattering properties of metallic nanostructures located at the Back side and optimize them for enhancing absorption in the silicon layer. We validate our numerical results experimentally and also compare the absorption enhancement in the solar cell structure, both with quasi-periodic and random metallic nanostructures. We have looked at the interplay between the metallic nanostructures and an integrated Back Reflector. We show that the combination of metallic nanoparticles and a metallic Reflector results in significant parasitic absorption. We compared this to another implementation based on titanium dioxide nanoparticles, which act as a Lambertian Reflector of light. Our simulation and experimental results show that this proposed configuration results in reduced absorption losses and in broadband enhancement of absorption for ultra-thin solar cells, paving the way to an optimal Back Reflector for thin film photovoltaics.
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broadband absorption enhancement in ultra thin crystalline si solar cells by incorporating metallic and dielectric nanostructures in the Back Reflector
arXiv: Mesoscale and Nanoscale Physics, 2013Co-Authors: S C Jain, Valerie Depauw, Vladimir D Miljkovic, Alexandre Dmitriev, Christos Trompoukis, Ivan Gordon, Pol Van Dorpe, Ounsi El DaifAbstract:We propose a Back-reflecting scheme in order to enhance the maximum achievable current in one micron thick crystalline silicon solar cells. We perform 3-dimensional numerical investigations of the scattering properties of metallic nanostructures located at the Back side, and optimize them for enhancing absorption in the silicon layer. We validate our numerical results experimentally and also compare the absorption enhancement in the solar cell structure, both with quasi-periodic and random metallic nanostructures. We have looked at the interplay between the metallic nanostructures and an integrated Back-Reflector. We show that the combination of metallic nanoparticles and a metallic Reflector results in significant parasitic absorption. We compared this to another implementation based on titanium dioxide nanoparticles which act as a lambertian Reflector of light. Our simulation and experimental results show that this proposed configuration results in reduced absorption losses and in broadband enhancement of absorption for ultra-thin solar cells, paving the way to an optimal Back Reflector for thin film photovoltaics.
