Al2O3 deposition has received a lot of attention in the last few years for its attractive passivation properties of c-Si surfaces. Within the local Al back-surface field (BSF) cell concept, we considered several avenues of study: surface preparation, thermal stability, charge investigation and the ‘blistering’ phenomenon. The investigations converged on a passivation stack that includes a thin interfacial SiO2 like layer and a thin Al2O3 layer (~10nm), which undergoes a high-temperature anneal (> 600°C). In order for a surface passivation with Al2O3 to be a cost-effective step for the PV industry, a high Al2O3 deposition rate is required. Compared to the different high-throughput tools that have recently emerged on the PV market, such as atomic layer deposition (ALD) and plasma-enhanced chemical vapour deposition (PECVD), our tool screening revealed quite similar results. The differences therefore seem to have an origin primarily in the tool specifications rather than in the achievable Al2O3 material properties.
t is well known that the cost of silicon materials is the major cost factor in crystalline silicon PV module production. Polysilicon price accounts for about 30% of total module production costs. While the PV industry has set a polysilicon price target of US$40/kg by 2015, this goal will not be reached if demand continues to exceed supply and if new plants cannot reduce operating costs below US$25/kg. Given a continued 30% annual growth in demand for PV modules, new polysilicon plants and expansions are needed to avoid shortages of high-purity, cost-effective polysilicon. This paper discusses the major factors in polysilicon production costs, the important elements of polysilicon plant design for reducing operating costs, the key cost elements of polysilicon plant operations, and how the design of polysilicon products can reduce crystal growth costs.
In recent years, Germany has seen impressive growth in its PV market. From a virtually non-existent market based on the 1,000 roof support program at the end of the 1990s, Germany now represents the world’s biggest PV market and has created a strong PV industry base. With approximately 17GW of installed PV capacity at the end of 2010 – accounting for 2% of its electricity consumption, Germany has become a solar super power and triggered market growth and technology development worldwide. Nevertheless, the innovative scheme of feed-in tariffs (FiT), which provided incentives for solar PV installations and helped to ramp up an unknown cycle of innovation, will have to evolve towards more diversified ways of supporting system transformation of the electricity market and PV market integration until full competiveness of PV technology is reached in Germany, anticipated for 2017.
Various economic and political influences continue to push high-volume manufacturing of semiconductor and PV devices into relatively arid and water-constrained geographies. As the social, economic and political focus on water resources and sustainability increases daily, the need to address the supply, use and disposal of water at manufacturing facilities is growing increasingly more complex. Historically, PV manufacturing has not been considered a major water consumer so there has been little scrutiny of water management. As the costs of water and wastewater disposal spiral upwards, water resource management becomes a significantly more important factor in the capital and operating costs of PV manufacturing. This paper outlines the preparation of a water management diagram (WMD) with reference to the development of water systems for new PV manufacturing plants, and discusses some cautionary design considerations.
The need for higher efficiency solar cells is becoming more and more urgent nowadays in the photovoltaic industry. In this paper, a new method of increasing efficiency is described whereby SiN is coated by a special commercial chemical after the final step of manufacturing, which is screen printing. No mask is required for this method, but a drying temperature of 200–400°C is mandatory to activate the SiN layer. It is shown that the efficiency of a crystalline solar cell can be increased by at least 0.16% (absolute value) on average. At the same time, modules made from these solar cells do not degrade after sun exposure, and have the potential to pass the stringent standards of a potential-induced degradation (PID) test. The total cost for all the equipment and the chemical is around US$300,000 for retrofitting two (30MW each) production lines.
To make solar energy cost effective, the photovoltaic (PV) industry has to reduce its manufacturing costs well below 1€/Wp. To reach this cost target, roadmaps for c-Si technology foresee a drastic reduction in the amount of high-purity Si used and an increase in solar cell efficiencies beyond 20%. But this requires advanced cell concepts that put more stringent requirements on process steps such as doping, cleaning and surface passivation. Several processes in the technology and analysis toolbox of microelectronics offer opportunities to meet these stringent requirements. In this paper, we give examples of recent progress in solar cell development that has been achieved by implementing CMOS-like process steps, and we discuss how these processes can be attuned to the needs and benefits of the solar industry.
The new German BDEW MV guideline demands static and dynamic functionalities from distributed energy resource (DER) units in order to support network operation and stability. Initial indications show that, in general, photovoltaic (PV) inverters are able to fulfil both the static and the dynamic requirements. Besides the new requirements of the guideline, an extensive certification process for DER units and plants has also been introduced. During initial certification processes, a significant need for PV-specific test procedures and test equipment has been determined. This article describes the developments within this area from the perspective of a measurement institute.
Our largest issue to date at 224 pages, the 13th edition of the Photovoltaics International journal features a focus on myriad topics including wafering and wire-sawing thermodynamics, the passivation benefits of ALD, reactive magnetron sputtering, PV module degradation and inverter certification. Contributors include imec, Fraunhofer IST, Motech Industries, PI Berlin, University of Toledo and CH2M HILL.
As the solar photovoltaic industry has matured from MW-scale pilot plants to large-scale mass manufacturing, costs of solar cells have steadily fallen. To further drive down costs of solar electricity beyond grid parity, a new approach that is being used is to investigate how photovoltaic manufacturing fits into the industrial ecology of a region. Optimizing the utilization of the waste associated with photovoltaic manufacturing itself and its components, while carefully considering geographic proximity, allows for industrial symbiosis. Industrial symbiosis engages traditionally separate industries in a collective approach to competitive advantage, involving physical exchange of materials, energy, water and/or by-products. Preliminary studies and industrial experimentation with co-production/co-location indicate that industrial symbiosis in photovoltaic manufacturing not only improves photovoltaic technology’s already stellar life-cycle environmental performance, but also provides for additional revenue streams that can be used to further reduce photovoltaic device costs. For example, simply coupling a glass manufacturing plant making substrates to a GW-scale amorphous silicon thin-film photovoltaic manufacturing plant, and using recycled glass where technically viable, can lead to a reduction of 30,000 tons/year in raw materials and a 12% reduction in embodied energy. Coupling the glass plant to a greenhouse to make use of waste heat means that more than 700 tons of tomatoes can be grown each year. Both these material and energy savings and additional revenue streams contribute to lowering photovoltaic manufacturing costs, which will play a progressively more important role in photovoltaic manufacturing at the large (>GW) scale.
The low material cost and proven manufacturability of thin-film silicon has made this material very attractive for low-cost photovoltaics (PV). It is widely recognized that increasing the light-to-electricity conversion efficiency will play a critical role in expanding the acceptance of these products. The first commercial thin-film silicon solar cell consisted of a singlejunction structure using amorphous silicon; multijunction cells incorporating amorphous silicon and silicon germanium were later used to further improve efficiency. An even later development was the incorporation of nanocrystalline silicon as an active layer. This very interesting material, which consists of nanocrystallites embedded in an amorphous tissue, has already given rise to a significant increase in the performance of these multijunction cells. Most recently, some very innovative light-trapping concepts have been suggested that can improve the efficiency further. Both these topics, however, have required expertise not readily available within one organization. A thin-film silicon team has been established under a US Department of Energy’s Solar America Initiative programme to address the material, device and manufacturability issues for this technology. United Solar Ovonic is the team leader, with Colorado School of Mines, University of Oregon, Syracuse University and the National Renewable Energy Laboratory (NREL) as members. The collaborative effort has resulted in a new understanding of the material and devices; innovative light trapping ideas were developed, and worldrecord initial efficiencies of 16.3% for small-area cells and 12% for large-area encapsulated cells were reached. Of equal importance is United Solar’s decision to introduce this technology into production. This paper presents the important technical results obtained under this programme and will discuss future directions.
