Technical Papers

Cell interconnection is recognized as the most critical process with respect to module production yield. If the process is not carefully controlled, cell cracking and subsequent breakage may occur. Many manufacturers promise breakage rates below 0.3-0.5% on their tabber-stringers, which applies for cells above 160-180µm thickness that are free from initial cracks. In real production, this figure strongly depends on materials, process parameters and throughput. This paper outlines some approaches that should be taken to avoid high levels of breakage in the cell interconnection process.

With the never-ending need to reduce production costs, interest in atmospheric deposition techniques is steadily increasing. Even though atmospheric deposition is not new to photovoltaics, and in some cases is actually required to get the best cell performance, many of the fabrication processes for photovoltaic cells are vacuum-based. Due to the diversity in atmospheric deposition techniques available, there are opportunities for applications in thin film and patterned deposition. This paper discusses some of the deposition techniques and their applications, benefits and drawbacks.

The upper and lower houses of the German parliament took their time finding a compromise on the degression of PV tariffs. Cutbacks were finally decided on at the start of July. The German PV market is now headed for another record-breaking year in 2010 despite or maybe even as a result of these reductions. EuPD Research, the market research institute, is making a conservative projection of approximately 5.5GW in newly-installed capacity. Nevertheless, pressure is set to increase, particularly on German solar companies. New marketing strategies have to be developed in the mid-term in order to survive and explore new segments in the long term.

The photovoltaic market, which is dominated by polysilicon-based crystalline solar cells, has been developing rapidly, with growth rates in the double-digit range for several years. In order to meet increasing demand for hyperpure polysilicon, manufacturers need to adhere to environmentally-friendly production processes with low energy consumption. This article highlights the key processes needed to manufacture hyperpure polycrystalline silicon and explores the related challenges and solutions for sustainable polysilicon production. Our findings prove that only an intelligent interaction of all necessary process steps fulfils the requirements for minimized production residue volumes and low energy consumption. Totally integrated production loops for all essential media are prerequisite to reach these targets. Once implemented, these highly efficient production processes serve as an excellent platform technology for the continued healthy growth of the PV industry.

A recent spate of solar cell efficiency gains and record results underline the continued efforts to boost conversion efficiencies, which are at the core of reducing cost-per-watt goals. However, bringing such technology into the mainstream volume production world at little or no increase in manufacturing cost will prove more challenging. This paper takes a look at the current mainstream c-Si cell metallization efficiency developments that are starting to enter volume production with a promise of 20% cell efficiencies and low manufacturing costs.

Thin-film solar photovoltaic technology offers the benefits of low-cost and high-volume production. Yet numerous thin-film PV startups have struggled in their efforts to commercialize complex, expensive production technologies, as production ramps have taken longer than expected, and venture capital and other sources of funding have run dry. This article describes a proprietary cadmium telluride (CdTe) thin-film module production process commercialized by Abound Solar: heated-pocket deposition (HPD) of the semiconductor layer, and the replacement of a traditional lamination process with a novel edge seal. The simple production process has resulted in a fast ramp of module efficiency and throughput. The paper will also describe how the process also results in fast throughput, high yields, and low manufacturing and capital equipment costs.

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 supply arrangements as a last resort.

This paper describes the functionality, applicability, and the development of dependency maps which are the basis for standardized information exchange between responsible parties during the fab design process. Examples and experiences are related to the solar industry; however this generic approach may be applied to a wide range of different industry sectors with similar challenges. The aim is to provide a guideline for realizing a fab design of dynamic and complex production systems. Its main benefit is a higher degree of transparency regarding dependencies within the production system, which results in a reduction of risk for incorrect planning. In addition, it enables the factory designer to execute the fab planning process and further continuous improvements for achieving respective targets.

Multicrystalline wafers are the workhorse of the PV industry, with approximately 60% of crystalline silicon solar cells made from the substrate. They offer cost advantages in the form of good conversion efficiencies, which should continue to improve as cell technology advances continue. However, wafer prices were acutely impacted by the fall in PV market demand in late 2008, which continued through most of 2009. With relatively high capital costs, continued pricing pressures and calls for greater quality and control, wafer producers are now set on a course that requires rigorous and sustainable production cost-reduction strategies to meet customer requirements. This paper focuses on strategies that can be adopted to address this need for tighter quality specifications that reduce manufacturing costs downstream and boost cell conversion efficiencies.

Development of fine-line crystalline silicon solar cells is a potential direction for application of high-efficiency and low-cost solar cells in the industry. Fine-line mask-free metallization offers a great potential to increase cell efficiency by reducing metal shadowing losses and surface recombination losses. At China Sunergy, three promising approaches for fine-line crystalline silicon solar cells are currently undergoing research, including processes such as laser doping selective emitter (LDSE) technology, inkjet or aerosol jet printing of metal paste and upgraded screen-printing technology. This paper presents the basic investigations of these three manufacturing technologies, singling out the technology that presents the most potential for further application.