Technical Papers

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Cell Processing, Photovoltaics International Papers
Phosphorus dopant pastes are an attractive alternative to the conventional phosphorus oxychloride (POCl3) dopant source for emitter processing in solar cells, as they allow the fabrication of selective emitters on an industrial scale. In this paper it is demonstrated that single-sided uniform screen-printed emitters, processed with phosphorus dopant pastes, can getter multicrystalline silicon (mc-Si) wafers more effectively than conventional double-sided uniform POCl3 emitters. This result is confirmed by minority carrier lifetime measurements with the quasi-stead-state photoconductance (QSSPC) method. Solar cells with selective emitters were processed using phosphorus dopant pastes on mc-Si wafers and were subsequently characterized. The current-voltage (I-V) results are improved compared to uniform POCl3 emitter solar cells and an increased internal quantum efficiency (IQE) for selective emitter solar cells is demonstrated.
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Cell Processing, Photovoltaics International Papers
Technology computer-aided design (TCAD) is pervasive throughout research, development and manufacturing in the semiconductor industry. It allows very low-cost evaluation of process options and competing technologies, guides process development and transfer to production and supports more efficient process improvement with minimal down time in the factory environment. This paper reviews the use of TCAD in the semiconductor industry and shows, with some illustrative examples, its important enabling role for the PV industry.
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Photovoltaics International Papers, Power Generation
Exceptional demand characterized the PV industry in 2010. Uncertainty regarding incentive schemes in a number of key markets drove global installations, and inverter shipments grew by over 160% as investors and developers rushed to complete projects, fearing that incentives would be reduced or removed altogether. IMS Research estimates that inverter shipments exceeded 20GW in 2010 and sales of small three-phase inverters, rated between 10-20kW, grew by around 200% in 2010. Inverters rated at over 500kW are estimated to have grown at a similar rate, but continue to represent a smaller share of revenues.
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Market Watch, Photovoltaics International Papers
The behaviour of PV markets over the last decade in Europe has taught us that not only it is necessary to optimally design support schemes, but that priority access to the grid for renewable energy sources and the reduction of administrative barriers are the key market drivers for sustainable development and essential for the markets to sustainably develop in the long term. This paper provides an overview of Europe’s PV market performance and delivers policy recommendations by means of EPIA’s PV Observatory model.
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Cell Processing, Photovoltaics International Papers
Processing silicon substrates for PV applications involves texturing, cleaning and/or etching wafer surfaces with chemical solutions. Depending on the cleanliness of the industrial equipment and the purity of the chemical solutions, surface contamination with metals or organic residues is possible [1]. The presence of trace contamination at PV junctions leads to both mid-level traps and photonic defects, which ultimately cause reduced efficiency and rapid cell degradation. Metallic impurities have a greater impact on PV cell lifetime due to their deeper energy levels in the silicon band gap [2]. On the other hand, non-metallic impurities may modify the electrical activity of PV cells because these species involve complex interactions with the host silicon lattice and its structural defects. In other words, very small amounts of contamination can result in poor PV efficiency. This paper presents an overview of the effects of adding a biodegradable complexing agent in cleaning and rinsing baths to minimize surface contamination and thereby enhance solar cell efficiency.
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Photovoltaics International Papers, PV Modules
After the encapsulation step, a c-Si solar module’s output is usually decreased, in comparison to its cells’ power, which is referred to as ‘power loss’. This paper focuses on the various factors that can impact power loss of solar modules, such as solar cell classification, encapsulation material, match of solar cells, the encapsulation process used, and so on. The conclusion indicates that power loss in solar modules can be significantly decreased with a resulting increment of a module’s output by appropriately optimizing those factors.
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Photovoltaics International Papers, PV Modules
Solar enterprises will each be faced with the occasional surplus or lack of solar modules in their lifetimes. In these instances, it is useful to adjust these stock levels at short notice, thus creating a spot market. Spot markets serve the short-term trade of different products, where the seller is able to permanently or temporarily offset surplus, while buyers are able to access attractive offers on surplus stocks and supplement existing supplyarrangements as a last resort.
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Cell Processing, Photovoltaics International Papers
This paper reviews the status of solar cell technology based on n-type crystalline silicon wafers. It aims to explain the reasons behind the strong and increasing attention for n-type cells, including the inherent advantages of n-type base doping for high diffusion length, and for the industrialization of designs with good rear-side electronic and optical properties. The focus will be on cells using diffused junctions.
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Photovoltaics International Papers, PV Modules
Since the 1980s, ethylene-vinyl acetate (EVA) has been the standard encapsulation material for crystalline photovoltaic modules. From a mechanical point of view, the encapsulant takes the function of a compliant buffer layer surrounding the solar cells. Therefore, understanding its complex mechanical properties is essential for a robust module design that withstands thermal and mechanical loads. In the cured state after lamination, its stiffness features a high sensitivity to temperature especially in the glass transition region around -35°C, and a dependence on time which becomes obvious in relaxation and creep behaviour. This paper outlines the viscoelastic properties of EVA and the corresponding standard experimental methods, as well as the impact on the accuracy of wind and snow load test procedures for PV modules.
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Cell Processing, Photovoltaics International Papers
Quality assurance and process control are becoming increasingly important in the industrial production chain to the manufacturing of silicon solar cells. There are a number of relevant wet chemical processes for the fabrication of standard screen-printed industrial solar cells, mainly for texturization and cleaning purposes. While one-component systems like pure HF for oxide-removal are easy to monitor, i.e., by conductivity measurements, typical texturization processes are much more complex due to the number of constituents. For acidic texturization of multicrystalline silicon wafers, typical mixtures involve amounts of hydrofluoric acid (HF), nitric acid (HNO3) and water. It has also been documented that mixtures can be found where additional additives like phosphoric acid (H3PO4), acetic acid (HOAc) and sulphuric acid (H2SO4) have been used [1, 2]. In alkaline random pyramid texturization for monocrystalline wafers, a base like potassium hydroxide (KOH) or sodium hydroxide (NaOH) and organic additives like 2-propanol (IPA) are used [3]. In addition to these processes, recently developed high-efficiency cell concepts require several additional wet chemical process steps like advanced cleaning processes, chemical edge isolation or single side oxide removal processes [4]. In order to obtain continuously stable and reproducible process results and to overcome process operations based on operator experience, a reliable monitoring of the bath concentrations is essential. Such quality control has the potential for significant cost reductions due to optimized durations between replacements of bath mixtures or shortening of processing times. In this context, the application of on-line analytical methods, either by means of chemical, optical or electrical measurement techniques, is of particular interest.

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