Injection-dependent Minority Carrier Lifetime in Epitaxial Silicon Layers by Time-resolved Photoluminescence

AbstractTime-resolved photoluminescence (TRPL) is used to evaluate the injection-dependent effective minority carrier lifetime of high resistivity epitaxial silicon layers grown on highly doped CZ-Si substrates. Effective lifetimes ranging from 10μs to 200μs are estimated for excess carrier densities between 1x1017 cm-3 and 2x1016 cm-3. Standard models are used to separate the contribution from the different recombination mechanisms. The influence of the epitaxial layer and substrate parameters on the minority carrier effective lifetime measurement is discussed

Hard UV-curable organo-mineral coatings for optical applications

Organically-modified silicate incorporating various amounts of zirconium precursor was synthesized via a sol-gel route. The material was deposited as thin films on PMMA substrates and densified by UV-curing. Mechanical properties were measured by nanoindentation and data were recorded continuously as a function of the penetration depth during the loading-unloading cycles. Values of hardness and Young modulus were found in the range 340 to 440 MPa and 4 to 6 GPa respectively. It was shown that these values could be tailored by varying the relative amount of zirconium in the layer. The material exhibited a very elastic behaviour that was related to its high degree of cross-linking assessed by infrared spectroscopy. Results were compared with measurements published by various groups on related materials. The mechanical and optical properties of the samples made this class of material promising as hard coatings for optical applications

Organo-silica titania nanocomposite elaborated by sol-gel processing with tunable optical properties

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Bifacial crystalline silicon homojunction cells contacted with highly resistive TCO layers

International audienceThis study explores the needed properties of Transparent Conductive Oxides (TCOs) for bifacial homojunctionsolar cells with potentially passivated contacts. TCO layers with different electrical and optical properties have been testedon both sides of n-type homojunction cells. The high lateral conductivity provided by the diffused emitter and back surfacefield (BSF) greatly reduces the constraints on TCO electrical properties in such structures. An understanding of the requiredproperties of TCO for advanced homojunction applications is given. Hence different O2-rich Indium Tin oxide (ITO) layersare analyzed optically and electrically before being implemented in homojunction solar cells to evaluate their influence onthe device performances. All in all moderately conductive TCOs are shown to be suitable for such applications, allowingbetter optical properties without inducing resistive losses in the devices

Self-processing of surface-relief gratings in photosensitive hybrid sol-gel glasses

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TCO contacts for high efficiency c-Si solar cells: Influence of different annealing steps on the Si substrates and TCO layers properties

International audienceDistrict heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand-outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations. Abstract Different Transparent Conductive Oxide (TCO) layers properties are evaluated after annealing steps at temperatures above 200°C, in order to study their potential use in crystalline silicon (c-Si) solar cells fabrication processes. While the conductivity of Indium Tin Oxide (ITO) layers obtained by magnetron sputtering (MS) is almost stable after annealing in air, Aluminum doped Zinc Oxide (AZO) layers deposited by Atomic Layer Deposition (ALD) need a controlled atmosphere to maintain high carrier densities and mobilities. During the annealing processes, contaminating atoms (such as Zn) diffuse into the c-Si bulk and may potentially decrease its quality. Thus, both the contamination of the c-Si bulk and the properties of the AZO layer have been analyzed. Abstract Different Transparent Conductive Oxide (TCO) layers properties are evaluated after annealing steps at temperatures above 200°C, in order to study their potential use in crystalline silicon (c-Si) solar cells fabrication processes. While the conductivity of Indium Tin Oxide (ITO) layers obtained by magnetron sputtering (MS) is almost stable after annealing in air, Aluminum doped Zinc Oxide (AZO) layers deposited by Atomic Layer Deposition (ALD) need a controlled atmosphere to maintain high carrier densities and mobilities. During the annealing processes, contaminating atoms (such as Zn) diffuse into the c-Si bulk and may potentially decrease its quality. Thus, both the contamination of the c-Si bulk and the properties of the AZO layer have been analyzed

TCO contacts on poly-Si layers: High and low temperature approaches to maintain passivation and contact properties

International audiencePolysilicon (poly-Si) based passivating contacts are promising to improve silicon solar cells conversion efficiency. Thin poly-Si layers usually feature high sheet resistances compared to conventional diffused junctions. Therefore the use of Transparent Conductive Oxides (TCO) has to be considered to improve lateral conductivity while maintaining good optical and surface passivation properties. Standard sputtered Indium Tin Oxide (ITO) can alter the poly-Si passivation properties. In this work different TCO-based contacts have been investigated (various materials and deposition techniques) in order to contact phosphorus-doped poly-Si layers (n+ poly-Si). The TCO-deposited samples experienced both low and high temperature annealing steps. Implied open circuit voltage above 730 mV and contact resistivity below 50 mΩ.cm2 at the TCO/n+ poly-Si interface have been obtained for both high and low temperature approaches. Thus such novel structures are very promising to contact poly-Si layers

Time-resolved photoluminescence for evaluating laser-induced damage during dielectric stack ablation in silicon solar cells

International audienceSelective laser ablation of dielectric layers on crystalline silicon wafers was investigated for solar cell fabrication. Laser processing was performed on Al2O3, and bi-layers Al2O3/SiNX:H with a nanosecond UV laser at various energy densities ranging from 0.4 to 2 J.cm-2. Ablation threshold was correlated to the simulated temperature at the interface between the dielectric coatings and the silicon substrate. Laser-induced damage to the silicon substrate was evaluated by time-resolved photoluminescence. The minority carrier lifetime deduced from time-resolved photoluminescence was related to the depth of the heat affected zone in the substrate

Time-resolved Photoluminescence for the Measurement of the Effective Carrier Lifetime in Si Photonic Structures

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