Pierre-Jean Alet

Forecasting and monitoring technologies for photovoltaics are required on different spatial and temporal scales by multiple actors, from the owners of PV systems to transmission system operators. In this paper the Grid integration working group of the European Technology and Innovation Platform – Photovoltaics (ETIP PV) reviews the different use cases for these technologies, their current status, and the need for future developments. Power system operations require a real-time view of PV… Mehr anzeigen

Forecasting and monitoring technologies for photovoltaics are required on different spatial and temporal scales by multiple actors, from the owners of PV systems to transmission system operators. In this paper the Grid integration working group of the European Technology and Innovation Platform – Photovoltaics (ETIP PV) reviews the different use cases for these technologies, their current status, and the need for future developments. Power system operations require a real-time view of PV production for managing power reserves and for feeding shortterm forecasts. They also require forecasts on all timescales from the short (for dispatching purposes), where statistical models work best, to the very long (for infrastructure planning), where physics-based models are more accurate. Power system regulations are driving the development of these techniques. This application also provides a good basis for a cost/benefit analysis since the forecasting error can be linked to the prices charged for energy imbalance. Weniger anzeigen

Integration in the power system is becoming a limiting factor to the further development of photovoltaics. Proper quantification is needed to evaluate both issues and solutions; the share of annual electricity demand is widely used but we found that some of the metrics which are related to power rather than energy better reflect the impact on networks. Barriers to wider deployment of PV into power grids can be split between local technical issues (voltage levels, harmonics distortion, reverse… Mehr anzeigen

Integration in the power system is becoming a limiting factor to the further development of photovoltaics. Proper quantification is needed to evaluate both issues and solutions; the share of annual electricity demand is widely used but we found that some of the metrics which are related to power rather than energy better reflect the impact on networks. Barriers to wider deployment of PV into power grids can be split between local technical issues (voltage levels, harmonics distortion, reverse power flows and transformer loading) and system-wide issues (intermittency, reduction of system resilience). Many of the technical solutions to these issues rely on the inverters as actuators (e.g., for control of active and reactive power) or as interfaces (e.g., for local storage). This role requires further technical standardisation and needs to be taken into account in the planning of power networks. Forecasting, storage, and combination with other renewable sources are interdependent solutions to solve the intermittency issue. Finally, we found that PV is also an opportunity to reduce some investment required to upgrade existing power networks. Through integration with micro-grids and hybrid generators, it can form the basis of novel power systems. Weniger anzeigen

The EU PV TP Strategic Research Agenda presents the view of a group of 29 PV experts (from industry and academia) of the research that should be started now in order to reach a defined set of cost targets by certain dates (2020 and 2030). Recommendations for research topics, often including a quantitative performance target relevant to that topic, are categorised according to the time by when it is likely that the results of the research or demonstration work are widely taken up by industry… Mehr anzeigen

The EU PV TP Strategic Research Agenda presents the view of a group of 29 PV experts (from industry and academia) of the research that should be started now in order to reach a defined set of cost targets by certain dates (2020 and 2030). Recommendations for research topics, often including a quantitative performance target relevant to that topic, are categorised according to the time by when it is likely that the results of the research or demonstration work are widely taken up by industry.
The SRA is addressed to the managers and strategists behind public research programmes at EU, national and sub-national level, and to CTOs in industry. Weniger anzeigen

Silicon nanowires (SiNWs) provide new opportunities for developing a new generation of thin film Si solar cells with enhanced light trapping and increased overall performance. Here, we report on the fabrication of SiNW-based thin film solar cells directly on top of low cost TCO/glass substrates in an all-in-situ process. The SiNWs are obtained on ITO (or SnO2) substrates via vapor–liquid–solid growth mechanism, with the nano-scaled In (or Sn) catalyst droplets prepared by using H2 plasma… Mehr anzeigen

Silicon nanowires (SiNWs) provide new opportunities for developing a new generation of thin film Si solar cells with enhanced light trapping and increased overall performance. Here, we report on the fabrication of SiNW-based thin film solar cells directly on top of low cost TCO/glass substrates in an all-in-situ process. The SiNWs are obtained on ITO (or SnO2) substrates via vapor–liquid–solid growth mechanism, with the nano-scaled In (or Sn) catalyst droplets prepared by using H2 plasma superficial reduction of ITO (or SnO2) in a plasma enhanced chemical vapor deposition system (PECVD). We demonstrate that the morphology and compositional properties of the SiNWs, as well as the catalyst remnant in the SiNWs, can be effectively controlled by tuning the growth temperature and plasma conditions. The enhanced light trapping and absorption effects have been achieved by growing SiNWs directly on top of the TCO substrates, with the absorption edge downshifting steadily to ∼1.1 eV, indicating that the crystalline core of the SiNWs also participates in the light absorption. According to a real time monitoring using an in-situ MM-16 ellipsometer, the enhanced light trapping/absorbing effects can be attributed to the growth of long, sharp and straight SiNW. Prototype SiNWs-based thin film solar cells are successfully demonstrated. Weniger anzeigen

Nano-structured silicon thin films have been grown on tin-doped indium oxide (ITO) by Plasma-Enhanced Chemical Vapor Deposition (PECVD) at temperatures lower than 200 °C. Nanometer-scaled aggregates of metal (copper or gold) obtained from evaporated layers were necessary to initiate the nano-structuring growth. Different deposition conditions have been investigated. The highest aspect ratio was obtained with copper and high-pressure plasmas with SiH4 diluted in H2. The metals help dissociating… Mehr anzeigen

Nano-structured silicon thin films have been grown on tin-doped indium oxide (ITO) by Plasma-Enhanced Chemical Vapor Deposition (PECVD) at temperatures lower than 200 °C. Nanometer-scaled aggregates of metal (copper or gold) obtained from evaporated layers were necessary to initiate the nano-structuring growth. Different deposition conditions have been investigated. The highest aspect ratio was obtained with copper and high-pressure plasmas with SiH4 diluted in H2. The metals help dissociating silane so the deposition starts faster on the aggregates than around them, which leads to nano-structuration. It is likely that the metal remains confined at the interface between ITO and silicon and do not diffuse in the silicon layer. Weniger anzeigen

Plasma-enhanced low temperature growth (<300 °C) of silicon nanowires (SiNWs) and hierarchical structures via a vapor–liquid–solid (VLS) mechanism are investigated. The SiNWs were grown using tin and indium as catalysts prepared by in situ H2 plasma reduction of SnO2 and ITO substrates, respectively. Effective growth of SiNWs at temperatures as low as 240 °C have been achieved, while tin is found to be more ideal than indium in achieving a better size and density control of the SiNWs… Mehr anzeigen

Plasma-enhanced low temperature growth (<300 °C) of silicon nanowires (SiNWs) and hierarchical structures via a vapor–liquid–solid (VLS) mechanism are investigated. The SiNWs were grown using tin and indium as catalysts prepared by in situ H2 plasma reduction of SnO2 and ITO substrates, respectively. Effective growth of SiNWs at temperatures as low as 240 °C have been achieved, while tin is found to be more ideal than indium in achieving a better size and density control of the SiNWs. Ultra-thin (4–8 nm) silica nanowires, sprouting from the dendritic nucleation patterns on the catalyst's surface, were also observed to form during the cooling process. A kinetic growth model has been proposed to account for their formation mechanism. This hierarchical structure combines the advantages of the size and position controllability from the catalyst-on-top VLS–SiNWs and the ultra-thin size from the catalyst-on-bottom VLS–ScNWs. Weniger anzeigen

Silicon nanowires have been grown with gallium as catalyst by plasma enhanced chemical vapor deposition. The morphology and crystalline structure has been studied by electron microscopy and Raman spectroscopy as a function of growth temperature and catalyst thickness. We observe that the crystalline quality of the wires increases with the temperature at which they have been synthesized. The crystalline growth direction has been found to vary between \langle 111\rangle and \langle 112\rangle… Mehr anzeigen

Silicon nanowires have been grown with gallium as catalyst by plasma enhanced chemical vapor deposition. The morphology and crystalline structure has been studied by electron microscopy and Raman spectroscopy as a function of growth temperature and catalyst thickness. We observe that the crystalline quality of the wires increases with the temperature at which they have been synthesized. The crystalline growth direction has been found to vary between \langle 111\rangle and \langle 112\rangle , depending on both the growth temperature and catalyst thickness. Gallium has been found at the end of the nanowires, as expected from the vapor–liquid–solid growth mechanism. These results represent good progress towards finding alternative catalysts to gold for the synthesis of nanowires. Weniger anzeigen

We report an in-plane solid-liquid-solid (IPSLS) mode for obtaining self-avoiding lateral silicon nanowires (SiNW) in a reacting-gas-free annealing process, where the growth of SiNWs is guided by liquid indium drops that transform the surrounding a-Si∶H matrix into crystalline SiNWs. The SiNWs can be ∼mm long, with the smallest diameter down to ∼22  nm. A high growth rate of >102  nm/s and rich evolution dynamics are revealed in a real-time in situ scanning electron microscopy observation. A… Mehr anzeigen

We report an in-plane solid-liquid-solid (IPSLS) mode for obtaining self-avoiding lateral silicon nanowires (SiNW) in a reacting-gas-free annealing process, where the growth of SiNWs is guided by liquid indium drops that transform the surrounding a-Si∶H matrix into crystalline SiNWs. The SiNWs can be ∼mm long, with the smallest diameter down to ∼22  nm. A high growth rate of >102  nm/s and rich evolution dynamics are revealed in a real-time in situ scanning electron microscopy observation. A qualitative growth model is proposed to account for the major features of this IPSLS SiNW growth mode. Weniger anzeigen

We here propose an all-in situ method for growing vapor–liquid–solid (VLS) silicon nanowires (SiNWs) directly on SnO2 substrates in a plasma-enhanced chemical vapor deposition system. The tin catalysts are formed by a well-controlled H2 plasma treatment of the SnO2 layer. The lowest temperature for the tin-catalyzed VLS SiNWs growth in a silane plasma is ~250 °C. The effects of substrate temperature and H2 dilution of silane on the morphology and compositional evolution of the SiNWs were… Mehr anzeigen

We here propose an all-in situ method for growing vapor–liquid–solid (VLS) silicon nanowires (SiNWs) directly on SnO2 substrates in a plasma-enhanced chemical vapor deposition system. The tin catalysts are formed by a well-controlled H2 plasma treatment of the SnO2 layer. The lowest temperature for the tin-catalyzed VLS SiNWs growth in a silane plasma is ~250 °C. The effects of substrate temperature and H2 dilution of silane on the morphology and compositional evolution of the SiNWs were systematically investigated. The catalyst content in the SiNWs can be effectively controlled by the deposition temperature. Moreover, enhanced absorption (down to ~1.1 eV) is achieved due to the strong light trapping and anti-reflection effects in the straight and long tapered SiNWs. Weniger anzeigen

In situ generation of indium catalyst droplets and subsequent growth of crystalline silicon nanowires on ITO by plasma-enhanced CVD are reported, and the wurtzite (Si–IV) phase is clearly evidenced in some wires.

The formation of gold islands on a transparent conductive oxide by annealing a thin evaporated layer is studied by SEM. The droplets of metal formed this way may catalyze the growth of nanowires or nanotubes to be used in opto-electronic devices. The effect of the initial thickness (between 1 nm and 4 nm) and the annealing temperature (between 70 °C and 650 °C) is investigated. A qualitative description of the evolution is given and quantitative data are obtained by automated image analysis… Mehr anzeigen

The formation of gold islands on a transparent conductive oxide by annealing a thin evaporated layer is studied by SEM. The droplets of metal formed this way may catalyze the growth of nanowires or nanotubes to be used in opto-electronic devices. The effect of the initial thickness (between 1 nm and 4 nm) and the annealing temperature (between 70 °C and 650 °C) is investigated. A qualitative description of the evolution is given and quantitative data are obtained by automated image analysis. Number density, area and effective diameter of the aggregates depend heavily on the initial thickness but very slightly on the annealing temperature. Three phenomena are considered to explain the evolution: interfacial stress due to mismatch in the linear expansion coefficient, Ostwald ripening and kinetic aggregation. By comparing the experimental size distributions to the theoretical ones, the relevance of the last two is discussed. As an application, the gold catalyzed CVD growth of silicon nanowires on zinc oxide is demonstrated. Weniger anzeigen

Hybrid concepts based on a nanoscale combination of organic and inorganic semiconductors are a promising way to enhance the cost efficiency of solar cells through a better use of the solar spectrum, a higher aspect ratio of the interface, and the good processability of polymers. A new type of solar cells has been investigated. It is based on a heterojunction between regio-regular poly(3-hexylthiophene) as an organic electron donor and silicon as an inorganic electron acceptor. In a first step… Mehr anzeigen

Hybrid concepts based on a nanoscale combination of organic and inorganic semiconductors are a promising way to enhance the cost efficiency of solar cells through a better use of the solar spectrum, a higher aspect ratio of the interface, and the good processability of polymers. A new type of solar cells has been investigated. It is based on a heterojunction between regio-regular poly(3-hexylthiophene) as an organic electron donor and silicon as an inorganic electron acceptor. In a first step towards nano-structured devices, cells made of flat thin films of these materials have been studied as a model case of the heterojunction. The materials were characterized through ellipsometry and absorption spectroscopy. The devices were studied by means of their spectral response and their I-V characteristics. By combining these results, the contribution of each layer and the mechanisms of photocurrent generation are explained. The best cells to-date show a power conversion efficiency of 1.6% under AM 1.5 illumination, with a V oc of 0.704 V and a J sc of 4.22 mA/cm2. Weniger anzeigen