Search

Evidence for the benefits of early palliative care (EPC) in patients with solid tumors is strong, but EPC has received scant attention in hematologic malignancies.To assess the benefits of outpatient-based EPC for symptom control in patients with multiple myeloma.Retrospective study of patients attending the Multiple Myeloma Palliative Care Clinic at our hospital in the year 2013 (February 1-December 31). The following symptoms were assessed at baseline and at three follow-up consultations using a Numerical Visual Scale (0 = no symptoms; 10 = worst possible): pain, anorexia, constipation, insomnia, nausea/vomiting, dyspnea, anxiety, and sadness. Physical and emotional symptom burden scores were calculated. Pain interference with general activity, sleep, and mood was also evaluated.About 67 patients were included. The proportion of patients reporting moderate-to-severe pain (Numerical Visual Scale ≥5) decreased significantly from baseline to the final follow-up: worst pain decreased from 57% to 18% (P 0.0001), whereas average pain fell from 24% to 2% (P 0.0001). The percentage of patients reporting no pain interference increased significantly from baseline: general activity (52% vs. 82%; P = 0.0001), sleep (73% vs. 91%; P = 0.01), and mood (52% vs. 87.5%; P = 0.0001). Physical and emotional symptom burden also improved, with significantly fewer patients reporting depression (13% vs. 5%; P = 0.001). Most patients (86.6%) were alive and still attending the Multiple Myeloma Palliative Care Clinic at study end.These findings indicate that EPC is feasible in patients with multiple myeloma. Pain and other symptoms were well controlled.

Silicon heterojunction solar cells without metallization can be interconnected using SmartWire Connection Technology (SWCT). The module performances can be comparable to standard SWCT module and the electrical contact of wire to transparent conductive oxide (TCO) is stable during more than 200 thermo-cycles between -40°C to +85°C. Costs comparison shows that direct contact to TCO is still more expensive than standard SWCT using indium-tin coating. By switching to indium-free wire, the cost parity can be reached.

Thin film tandem solar cells based on amorphous and microcrystalline silicon (MicromorphTM in superstrate configuration) benefit from strongly light-scattering nano-textured substrates. A development methodology for the evaluation of the performance of the Micromorph test cells deposited on such substrates with very different surface shapes is presented and illustrated. It is shown that growth related defects and non-conformal coverage of the silicon layers restrict the choice of surface shapes for this photovoltaic application. General guidelines are given in this study for the preferred selection of the surface geometry for MicromorphTM test cells. The results indicate that the application of advanced surface shapes for higher conversion efficiencies requires improved silicon deposition process compared to current industrial state-of-the-art.

This short communication highlights our latest results towards high-efficiency microcrystalline silicon single-junction solar cells. By combining adequate cell design with high-quality material, a new world record efficiency was achieved for single-junction microcrystalline silicon solar cell, with a conversion efficiency of 10.69%, independently confirmed at ISE CalLab PV Cells. Such significant conversion efficiency could be achieved with only 1.8 µm of Si.

Strengthening climate change resilience in Africa is of real concern. Energy demand across the continent is on the rise due to expanding populations, economic progress and lifestyle changes. Without a sustainable increase in supply, much needed economic growth will be reined in. Africa, because of its renewable energy resource base, is in a unique position to pursue sustainable energy development which can be a determinant of climate change resilience. However, the eastern region of the contintent is facing serious energy deficits and high energy costs. The ENRICH and the SUCCEED Network Projects, funded through the European Union’s EU—ACP cooperation S&T and Edulink II instruments, aim to plant the seeds of change through increased capacity in sustainable energy development. Output from these projects takes the form of an STI support network and development of university campuses as ‘living laboratories’. These new and ‘dynamic systems’ have inbuilt engineered resilience to foster efficiency and as they evolve, natural resilience to promote rapid adaptation to cope with existing and emerging knowledge and informational vulnerabilities. This paper considers how such responses at campus level can strengthen resilience at national level to mitigate the effects of climate change.

This paper gives new insights into the role of both the microstructure and the interfaces in microcrystalline silicon (μc- Si) single-junction solar cells. A 3-D tomographic reconstruction of a μc-Si solar cell reveals the 2-D nature of the porous zones, which can be present within the absorber layer. Tomography thus appears as a valuable technique to provide insights into the μc- Si microstructure. Variable illumination measurements enable to study the negative impact of such porous zones on solar cells performance. The influence of such defectivematerial can bemitigated by suitable cell design, as discussed here. Finally, a hydrogen plasma cell post-deposition treatment is demonstrated to improve solar cells performance, especially on rough superstrates, enabling us to reach an outstanding 10.9% efficiency microcrystalline singlejunction solar cell.

In this work, it is shown that variations in the ratio of oxygen to zinc precursors at constant temperature allow changing the surface morphology of zinc oxide (ZnO) films deposited by lowpressure metalorganic chemical vapor deposition, while keeping the sheet resistance and transparency of the layers constant. This allows developing ZnO layers combining interesting properties such as low surface roughness (below 15 nm) and low sheet resistance (below 15 O/&). More generally, it is shown that the pyramidal feature density can be controlled by tuning the precursor flows. This leads to film surfaces characterized by zones with a rough morphology mixed with zones with almost flat features. Therefore, by using this technique, the light-scattering ability of a film can be carefully tuned through its surface morphology without affecting the conductivity or transparency of the layer. This provides an efficient tool to optimize the front electrode of thin-film silicon solar cells to achieve the best possible combination of open-circuit voltage, fill factor and photo-generated current. The presented solution is an in-situ process achievable in standard deposition conditions making it easily up-scalable with existing production equipment.

Optimized transparent conductive oxide front electrodes are vital to further increase the efficiency of thin film silicon solar devices. We report details on the fabrication of multiscale textured zinc oxide substrates and their implementation in amorphous silicon/microcrystalline silicon tandem (micromorph) devices. Such substrates allow separate optimization of light trapping in the top and bottom cells and efficient decoupling of transparency and conduction. We show in particular the need for sharp nanoscale texturing for antireflection and light trapping in the top cell. We also show that smooth micrometer scale texturing can efficiently improve large wavelength light management without degrading the quality of the silicon material grown on the substrate. By combining the appropriate morphologies high currents can be reached in both the top and bottom subcells while conserving the optimal electrical properties of the solar cells. © 2011 IEEE.

The imprinting of random square based pyramidal textures with micrometric scale at the air/glass interface of thin film silicon solar cells is presented as an efficient alternative to anti-reflective coatings to minimize reflection losses at the cell entrance. This novel processing step, which can be applied after cell or module manufacture, is found to simultaneously enhance light in-coupling and light-trapping in amorphous silicon/microcrystalline silicon tandem solar cells. A remarkable total current gain of more than 5% is demonstrated with the imprinting of such structures, resulting in a tandem cell with a high initial efficiency of 13% for a total absorber layer thickness below 1.5 mu m. (C) 2011 Elsevier B.V. All rights reserved.

The challenge for all photovoltaic technologies is to maximize light absorption, to convert photons with minimal losses into electric charges, and to efficiently extract them to the electrical circuit. For thin-film solar cells, all these tasks rely heavily on the transparent front electrode. Here we present a multiscale electrode architecture that allows us to achieve efficiencies as high as 14.1% with a thin-film silicon tandem solar cell employing only 3 μm of silicon. Our approach combines the versatility of nanoimprint lithography, the unusually high carrier mobility of hydrogenated indium oxide (over 100 cm(2)/V/s), and the unequaled light-scattering properties of self-textured zinc oxide. A multiscale texture provides light trapping over a broad wavelength range while ensuring an optimum morphology for the growth of high-quality silicon layers. A conductive bilayer stack guarantees carrier extraction while minimizing parasitic absorption losses. The tunability accessible through such multiscale electrode architecture offers unprecedented possibilities to address the trade-off between cell optical and electrical performance.

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/cm 2 of 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. © 2011 Elsevier B.V. All rights reserved.

Nanopatterning has gained tremendous importance in the field of photovoltaics, as absorption of sunlight in solar cells can be enhanced drastically by proper engineering of photonic nanostructures1– 8. However, despite intensive efforts, neither the ideal surface morphology nor the ideal scattering characteristics foroptimumlight trapping have been identified. Experimentally, a method capable of implementing arbitrarily designed surface morphologies directly into functional devices is desirable. Here, we establish a nanomoulding process that provides exactly such a platform, enabling precise, large-area, nanoscale patterning of functional zinc oxide films at low cost. We illustrate the application of nanomoulded zinc oxide films as transparent front electrodes in amorphous silicon solar cells, demonstrating excellent initial conversion efficiencies of 10.1%. In the quest to find the most efficient light-harvesting scheme, we anticipate that nanomoulding will catalyse the development and integration of exciting new nanophotonic structures.

We demonstrate high-efficiency thin-film silicon solar cells with transparent nanotextured front electrodes fabricated via ultraviolet nanoimprint lithography on glass substrates. By replicating the morphology of state-of-the-art nanotextured zinc oxide front electrodes known for their exceptional light trapping properties, conversion efficiencies of up to 12.0% are achieved for micromorph tandem junction cells. Excellent light incoupling results in a remarkable summed short-circuit current density of 25.9 mA/cm(2) for amorphous top cell and microcrystalline bottom cell thicknesses of only 250 and 1100 nm, respectively. As efforts to maximize light harvesting continue, our study validates nanoimprinting as a versatile tool to investigate nanophotonic effects of a large variety of nanostructures directly on device performance.

Laser-controlled ablation of individual layers in glass/TCO/thin-film silicon/metal structures is essential for cell isolation and monolithic interconnection in thin-film silicon photovoltaic technologies. More recently, the potential application of laser scribing techniques for the development of photovoltaic matrix position sensors based on a-Si:H has generated much activity, requiring an excellent control in laser-generated patterns obtained by direct material ablation. This work is aimed to determine process parametric windows for a-Si:H thin-film ablation processes using UV ns laser sources in thin-film a-Si:H-based devices. The study is focussed on direct writing techniques using UV sources. We present ablation threshold measurements and process quality assessment using advanced optical microscopy techniques. Moreover only fully commercial laser sources in the ns regime has been used, bearing in mind that thin film based photovoltaic technologies are still demanding further reduction in production costs and, nowadays, ultrafast sources are beyond their scope both for the investment and running cost of those equipments.

The use of photovoltaic (PV) is not anymore an option but a real need in the construction of nearly zero energy buildings. To date, the lack of PV products specifically designed for building integration, considering aesthetics and architectural aspects, is one important limiting factor allowing a massive deployment of PV in the built environment. Architects are continuously asking for new solutions to customize the colour of PV elements to better integrate them into the building skin. Among these colours, white is especially attractive as it is widely used in architecture for its elegance, versatility and fresh look. Until now, white solar modules were not considered to be an option and even never been though to be a technological possibility. Nonetheless, CSEM recently developed a new technology to make white solar modules a reality. Furthermore, the new Swiss company called Solaxess is now working on the industrialisation of this very innovative technology and the first products are expecting to be on the market at the end of 2015. The technology is based on the combination of two different elements: a solar cell able to convert solar infrared light into electricity and a selective filter which reflects and diffuse the whole visible spectrum. Any PV technology based on crystalline silicon can be used as they have a good response in the infrared. Approximately 55% of the current generated under standard test conditions comes from the infrared leading to conversion efficiencies above 11%. We will demonstrate, that thanks to this very innovative technology PV modules can become attractive and real active building elements and therefore meets the requirements of any future energy management through advanced building skins.

CSEM in its photovoltaic activity has developed white solar modules with conversion efficiencies above 10%. This innovative PV technology is particularly attractive to be used in building industry where PV elements can blend into building skin and become virtually hidden energy sources. The new Swiss company called Solaxess is now working on the industrialization of this new technology and the first products are expected to be in the market at the end of 2015.

Amorphous and nanocrystalline silicon films obtained by Hot-Wire Chemical Vapor Deposition have been incorporated as active layers in n-type coplanar top gate thin film transistors deposited on glass substrates covered with SiO 2 . Amorphous silicon devices exhibited mobility values of 1.3 cm 2 V − 1 s − 1 , which are very high taking into account the amorphous nature of the material. Nanocrystalline transistors presented mobility values as high as 11.5 cm 2 V − 1 s − 1 and resulted in low threshold voltage shift (∼ 0.5 V).

Light confinement strategies in thin-film silicon solar cells play a crucial role in the performance of the devices. In this work, the possible use of Ag-coated stamped polymers as reflectors to be used in n–i–p solar cells is studied. Different random roughnesses (nanometer and micrometer size) have been transferred on poly(methylmethacrylate) (PMMA) by hot embossing. Morphological and optical analyses of masters, stamped polymers and reflectors have been carried out evidencing a positive surface transference on the polymer and the viability of a further application in solar cells.

We describe a nanomoulding technique which allows low-cost nanoscale patterning of functional materials, materials stacks and full devices. Nanomoulding combined with layer transfer enables the replication of arbitrary surface patterns from a master structure onto the functional material. Nanomoulding can be performed on any nanoimprinting setup and can be applied to a wide range of materials and deposition processes. In particular we demonstrate the fabrication of patterned transparent zinc oxide electrodes for light trapping applications in solar cells.

Silver can be used as the back contact and reflector in thin film silicon solar cells. When deposited on textured substrates, silver films often exhibit reduced reflectance due to absorption losses by the excitation of surface plasmon resonances. We show that thermal annealing of the silver back reflector increases its reflectance drastically. The process is performed at low temperature (150°C) to allow the use of plastic sheets such as polyethylene naphthalate and increases the efficiency of single junction amorphous solar cells dramatically. We present the best result obtained on a flexible substrate: a cell with 9.9% initial efficiency and 15.82 mA/cm2 in short circuit current is realized in n-i-p configuration.

We investigate the influence of refractive index contrast on the light scattering properties of nanotextured interfaces, which serve as front contact for p-i-n thin-film silicon solar cells. We here focus on ZnO surfaces with randomly oriented pyramidal features, known for their excellent light trapping performance. Transparent replicas, with a different refractive index, but practically identical morphology compared to their ZnO masters, were fabricated via nanoimprinting. Within the theoretical framework we recently proposed, we show how the angular and spectral dependence of light scattered by nanostructures with identical morphology but different refractive index may be related to each other allowing direct comparison of their light trapping potential within the device.

Angle resolved measurements of the external quantum efficiency of a-Si solar cells deposited on a grating show strong absorption phenomena which are well explained with the guided mode structure in an equivalent flat multilayer system.

Hydrogenated amorphous silicon has been widely studied last years, both from the basic research and industrial points of view, due to the important set of potential applications that this material offers, ranging from Thin Films Transistors (TFTs) to solar cells technologies. In different fabrication steps of a-Si:H based devices, laser sources have been used as appropriate tools for cutting, crystallising, contacting, patterning, etc., and more recent research lines are undertaking the problem of a-Si:H selective laser ablation for different applications. The controlled ablation of photovoltaic materials with minimum debris and small heat affected zone with low processing costs, is one of the main difficulties for the successful implementation of laser micromachining as competitive technology in this field. This work presents a detailed study of a-Si:H laser ablation in the ns regime. Ablation curves are measured and fluence thresholds are determined. Additionally, and due to the improved performance in optolectronic properties associated to the nanocrystalline silicon (nc-Si:H), some samples of this material have been also studied.

Hot-Wire Chemical Vapor Deposition has led to microcrystalline silicon solar cell efficiencies similar to those obtained with Plasma Enhanced CVD. The light-induced degradation behavior of microcrystalline silicon solar cells critically depends on the properties of their active layer. In the regime close to the transition to amorphous growth (around 60% of amorphous volume fraction), cells incorporating an intrinsic layer with slightly higher crystalline fraction and [220] preferential orientation are stable after more than 7000 h of AM1.5 light soaking. On the contrary, solar cells whose intrinsic layer has a slightly lower crystalline fraction and random or [111] preferential orientation exhibit clear light-induced degradation effects. A revision of the efficiencies of Hot-Wire deposited microcrystalline silicon solar cells is presented and the potential efficiency of this technology is also evaluated.

The use of polymer substrates for thin film solar cells is becoming an issue of great interest, as they facilitate monolithic interconnection of the cells to produce modules and can be used in continuous roll-to-roll processes. However, to reach high efficiencies of thin film silicon cells on polymer substrates, the development of efficient light confinement strategies has to be improved. In this work, hot embossing is used to produce a suitable surface morphology on PEN substrates. Three morphologies have been studied by using three selected masters. To evaluate the quality of the embossing, the morphology of the masters and that of the stamped PEN samples have compared. Finally, the stamped polymers have been covered with thin Ag and transparent conductive oxide (TCO) layers and whole reflectance experiments have been performed to asses the efficiency of the fabricated back reflectors

Double-sided (bifacial) heterojunction silicon solar cells have been fabricated by Hot-Wire CVD on both p- and n-type crystalline silicon substrates. In these devices, doped microcrystalline silicon layers are combined with thin intrinsic amorphous silicon buffers. Such heterojunction with intrinsic thin layer concept is applied to obtain both the low temperature deposited emitter and back surface field contact. Especially remarkable is the performance of the solar cell fabricated on p-type c-Si. This device yields a total area (1.4 cm2) conversion efficiency of 13.3%, with an open-circuit voltage of 619 mV, short-circuit current density of 29.0 mA cm- 2 and fill factor of 74.1%. The substrate temperature is kept below 200 °C during the whole fabrication process.

n and p-type nanocrystalline thin film transistors in coplanar top gate configuration have been processed at low temperature. All silicon layers (intrinsic, n and p-type) have been deposited by hot-wire chemical vapor deposition on glass substrates covered with SiO/sub 2/. Gate insulation has been achieved by means of high quality sputtered SiO/sub 2/. The maximum temperature reached during the whole process was 200/spl deg/C. Very high field effect mobility has been obtained for both kinds of devices, with values of 22 cm V/sup -1/s/sup -1/ for the electron mobility and around 1.0 cm V/sup -1/s/sup -1/ for the hole mobility.

The possible use of polyethylene naphthalate as substrate for low-temperature deposited solar cells has been studied in this paper. The transparency of this polymer makes it a candidate to be used in both substrate and superstrate configurations. ZnO:Al has been deposited at room temperature on top of PEN. The resulting structure PEN/ZnO:Al presented good optical and electrical properties. PEN has been successfully textured (nanometer and micrometer random roughness) using hot-embossing lithography. Reflector structures have been built depositing Ag and ZnO:Al on top of the stamped polymer. The deposition of these layers did not affect the final roughness of the whole. The reflector structure has been morphologically and optically analysed to verify its suitability to be used in solar cells.

El estudio de las coberturas y usos del suelo y su variación a lo largo del tiempo obedece a gran cantidad de fines: estudios medioambientales, económicos, sociales, planificación territorial (infraestructuras, urbanismo o agrícola), estratégicos, etc., como fuente de información y de diagnóstico geográfico, asimismo constituye un elemento clave en la toma de decisiones. El análisis de la evolución de las coberturas y usos del suelo en el tiempo desde una perspectiva multidisciplinar en la Marina Baixa permite la evaluación de las políticas llevadas a cabo y la anticipación para la adecuada orientación de actuaciones futuras. En este sentido, se considera conveniente poner a punto una metodología de entrada y tratamiento de los datos espaciales, basada en la utilización de Sistemas de Información Geográfica (S.I.G.) y fotografía aérea. El presente trabajo trata de mostrar y cuantificar la cronosecuencia de las coberturas y usos de suelo de la comarca de la Marina Baixa, como resultado de la tarea de fotointerpretación y cartografiado, sin atender a las causas que la motivan o las consecuencias que implican. Próximos estudios dentro del mismo proyecto incurrirán en los efectos sobre la biodiversidad vegetal y los balances hídricos para el periodo estudiado. The study of variations through time in land cover and land use as sources of information and geographical diagnosis, is due to many different factors: environmental, economical, social territorial planning (infrastructure, urban or farming planning), strategic research etc., and thus is a key element for decision makers. The analysis of the evolution of land cover and land use through time from a multidisciplinary point of view in the Marina Baixa allows for the evaluation of implemented policy as well as the anticipation of future planning policies. To this effect, we have developed a methodology of spatial data input and management, based on the use of Geographical Information Systems (G.I.S.) and aerial photographs. The present work attempts to demonstrate and quantify land cover and land use chronosequence of the Marina Baixa region, using photo-interpretation and cartographic work, without assessing the causes that motivate land use changes or their consequences. Forthcoming studies within the same project will include in the effects of vegetal biodiversity and hydrological balances over the study period.

Nutrient cycling is one of the major functional properties of ecosystems. The amounts of nutrients contained within the ecosystem, their distribution among ecosystem compartments, and their rates of flow between compartments reflect the interactions between organisms and their environment, and are an expression of the extent to which ecosystems affect and are affected by the availability and fate of nutrients (Attiwill and Adams 1993).

UV imprinting is an interesting, low cost technique to produce large area thin film solar cells incorporating nanometric textures. Here, we review and present new results confirming that replicas of the most common textures used in photovoltaics can be obtained by UV imprinting with an excellent fidelity. The use of these replicas as substrates for amorphous and micromorph thin film silicon solar cells is also shown, together with a comparison with devices obtained on the original textures.

We investigate the influence of the oxygen content in boron-doped nanocrystalline silicon oxide films (p-nc-SiOx) and introduce this material as window layer in n-i-p solar cells. The dependence of both, optical and electrical properties on the oxygen content is consistent with a bi-phase model which describes the p-nc-SiOx material as a mixture of an oxygen-rich (O-rich) phase and a silicon-rich (Si-rich) phase. We observe that increasing the oxygen content enhances the optical gap E-04 while deteriorating the activation energy and the planar conductivity. These trends are ascribed to a higher volume fraction of the O-rich phase. Incorporated into n-i-p a-Si: H cells, p-nc-SiOx layers with moderate oxygen content yield open circuit voltage (V-oc) up to 945mV, which corresponds to a relative gain of 11% compared to an oxygen-free p-layer. As a similar gain is obtained on planar and on textured substrates, we attribute the increase in V-oc to the higher work function of the p-nc-SiOx layer made possible by its wider band gap. These results are attained without changing the dilution ratio of the 250 nm thick intrinsic layer. We also observe an enhancement of 0.6mA cm(-2) in short circuit current density in the short wavelengths due to the higher transparency of the p-nc-SiOx layer. Finally, an initial efficiency of 9.9% for a single junction 250 nm a-Si:H n-i-p solar cell on plastic foil is achieved with the optimization of the p layer thickness, the doping ratio of the front transparent conductive oxide, and the optical properties of the back reflector. (C) 2011 American Institute of Physics. [doi:10.1063/1.3669389]

We investigate the performance of hydrogenated indium oxide as a transparent front electrode for micromorph thin-film silicon solar cells on glass. Light trapping is achieved by replicating the morphology of state-of-the-art zinc oxide electrodes, known for their outstanding light trapping properties, via ultraviolet nanoimprint lithography. As a result of the high electron mobility and excellent near-infrared transparency of hydrogenated indium oxide, the short-circuit current density of the cells is improved with respect to indium tin oxide and zinc oxide electrodes. We assess the potential for further current gains by identifying remaining sources of parasitic absorption and evaluate the light trapping capacity of each electrode. We further present a method, based on nonabsorbing insulating silicon nitride electrodes, allowing one to directly relate the optical reflectance to the external quantum efficiency. Our method provides a useful experimental tool to evaluate the light trapping potential of novel photonic nanostructures by a simple optical reflectance measurement, avoiding complications with electrical cell performance.

We describe a method based on nanoimprinting and non-absorbing insulating silicon nitride electrodes for evaluating the light trapping potential of photonic nanostructures for thin-film silicon solar cells. We validate our method by relating the optical reflectance of the full solar cell stack to the external quantum efficiency of functional cells. Our method provides a useful experimental tool to compare different nanostructures circumventing complications arising from parasitic absorption and electrical cell performance.

We propose the use of transparent replicated random nanostructures fabricated via nanoimprinting on glass as next-generation superstrates for thin film silicon solar cells. We validate our approach by demonstrating short-circuit current densities for p-i-n hydrogenated microcrystalline silicon solar cells as high as for state-of-the-art nanotextured ZnO front electrodes. Our methodology opens exciting possibilities to integrate a large variety of nanostructures into p-i-n solar cells and allows to systematically investigate the influence of interface morphology on the optical and electronic properties of the device in order to further improve device performance.

In Thin Film Silicon (TF-Si) solar cells light harvesting schemes must guarantee an efficient light trapping in the thin absorber layers without decreasing the silicon layers quality and consecutively the p-i-n diodes electrical performance. TF-Si solar cells resilience to the substrate roughness is reported to be possibly improved through optimizations of the cell design and of the silicon deposition processes. By further tailoring the superstrate texture, amorphous silicon / microcrystalline silicon (a-Si:H/mu c-Si:H) tandem solar cells with an initial efficiency up to 13.7 % and a stabilized efficiency up to 11.8 % are demonstrated on single-scale textured superstrates. An alternative approach combining large and smooth features nanoimprinted onto a transparent lacquer with small and sharp textures from as-grown LPCVD ZnO is then shown to have a high potential for further increasing TF-Si devices efficiency. First results demonstrate up to 14.1 % initial efficiency for a TF-Si tandem solar cell.

We investigate the transfer of random nanostructures commonly used in thin film silicon solar cells onto inexpensive substrates such as glass or flexible polyethylene sheets. Morphological and optical analyses of masters and replicas show the successful transfer of details with sizes much below 1 µm. These high quality replicas are obtained by UV nano imprinting avoiding the use of PDMS as an intermediate mold which has been identified as being responsible for the lack of resolution found in previous works. © 2010 Elsevier B.V. All rights reserved.

In this work, we study the replication of nanotextures used in thin film silicon solar cells to enhance light trapping onto inexpensive substrates such as glass or polyethylene naphtalate (PEN). Morphological analysis was carried out to asses the quality of these replicas. Moreover, single and tandem a-Si:H solar cells were deposited on top of the master and replica structures to verify their suitability to be used as substrates for solar cells in n-i-p configuration. We find stabilized efficiencies around 8% which are similar for tandem cells on masters and PEN replicas.

We give an overview on recent progress in the synthesis, fabrication and integration of advanced nanostructured materials for efficient light trapping in high-efficiency thin-film silicon solar cells.

Nowadays, one of the most important challenges to enhance the efficiency of thin film silicon solar cells is to increase the short circuit intensity by means of optical confinement methods, such as textured back-reflector structures. In this work, two possible textured structures to be used as back reflectors for n–i–p solar cells have been optically analyzed and compared to a smooth one by using a system which is able to measure the angular distribution function (ADF) of the scattered light in a wide spectral range (350–1000 nm). The accurate analysis of the ADF data corresponding to the reflector structures and to the μc-Si:H films deposited onto them allows the optical losses due to the reflector absorption and its effectiveness in increasing light absorption in the μc-Si:H layer, mainly at long wavelengths, to be quantified.

Angle resolved measurements of the external quantum efficiency of n-i-p single junction amorphous solar cell deposited on a grating structure show clearly defined peaks of enhanced photocurrent in the weakly absorbing region between 1.6 and 2.15 eV. We explain these absorption phenomena and their angular variation with the excitation of guided modes via grating coupling. Calculation using an equivalent flat multilayer system permits to relate the theoretical values with the experimental data.

Texturing of interfaces in thin film silicon solar cells is essential to enhance the produced photocurrent and thus the efficiencies.AUVnano-imprint-lithography (UV-NIL) replication processwas developed to prepare substrates with textures that are suitable for the growth of n-i-p thin film silicon solar cells. Morphological and optical analyses were performed to assess the quality of the replicas. A comparison of single junction amorphous solar cells on the original structures and on their replicas on glass revealed good light trapping and excellent electrical properties on the replicated structures. A tandem amorphous silicon/amorphous silicon (a-Si/a-Si) cell deposited on a replica on plastic exhibits a stabilized efficiency of 8.1% and a high yield of 90% of good cells in laboratory conditions. It demonstrates the possibility to obtain appropriate structure on low cost plastic substrate. Copyright © 2010 John Wiley & Sons, Ltd.