This paper discusses the wire sawing process and its impact on the wafer surface and subsurface. Surface damage is found to be the main determinant in wafer stability, while an outline of the sawing parameters that have a strong influence on the surface and subsurface damage is presented. The results indicate how it is possible to decrease the breakage rate of wafers and improve the homogeneity (e.g. TTV) of wafer surfaces. A further goal in the development of the wire sawing process is to successfully reduce material consumption. This can be achieved by sawing thinner wafers with thinner wires, which leads to a reduction of the kerf loss per produced silicon surface. The second option is to increase the material yield by decreasing the wafer breakage. It will be shown that silicon wafers with less and shorter cracks and smoother surfaces will give a higher yield, while proceeding to discuss some of the important factors that affect the microcrack formation.
Recent industry analysis from NanoMarkets has suggested that although current business cases for PV are running out of steam, the building-integrated PV (BIPV) sector may be able to revive PV’s fortunes. The arrival of ‘true’ BIPV – not just flush-mounted BIPV panels, but PV-enabled glass, tiles, siding, etc. – renders possible new business cases that would otherwise simply not be an option with conventional PV. This paper puts forth a business analysis of the BIPV industry, providing case studies and data on the burgeoning sector.
One of the busiest of the couple-dozen solar manufacturing factory floors I’ve seen this year belonged to ECD Uni-Solar, at its Auburn Hills 2 (AH2) facility just up the road from the Palace where the NBA’s Detroit Pistons play hoops. When I toured the plant in late July, the three production areas – cell
deposition, cell finishing, and module stringing/lamination/final assembly – were humming, as the 1.5-milelong rolls of flexible stainless-steel starting material were transformed into triplejunction amorphous-silicon thin-film PV laminates. The company’s latest quarterly results confirm those observations at the factory, as production output grew some 58% over the previous period – from 21.2MW to 33.6MW – pushing capacity utilization to about 90%.
A selective emitter is a doping layer that is heavily doped beneath the electrode and lightly doped in between the electrode grids. One of the disadvantages of conventional selective-emitter techniques is the need for a high phosphorus surface concentration to obtain low contact resistance and limit the shunts in the emitter. Effective emitter passivation below the contact is difficult because of the use of emitters with low sheet resistances and high doping concentrations. In this study, the selective emitter in the optimized light/light sheet-resistance combination was formed to reduce recombination under the metal contact. The fabrication of optimized light/light doped emitters was performed using a single-step diffusion process. Besides the benefit of low surface recombination for light/light combination, this approach also removes the need for a very precise alignment between the opened emitter pattern and the front screen-printed silver fingers. This work illustrates the achievement of an efficiency improvement of more than 0.4% absolute in large-scale production for selective emitter solar cells.
The workhorse of the photovoltaic industry, crystalline-silicon solar cells, continues to have additional headroom for conversion efficiency improvement as well as decreased production costs. As some companies have already demonstrated, clear pathways exist to bring about the achievement of >20%-efficient monocrystalline cells through the use of existing and novel production techniques. A newcomer to the solar cell and module sector, Suniva, has rapidly become a volume manufacturer using innovations originally developed at the University Center of Excellence in Photovoltaics (UCEP) at the Georgia Institute of Technology. This paper discusses the company’s first- and second-generation production technologies, including the implementation of ion implantation as a high-volume process, as well as details of cell-making approaches in the development stage.
Laser grooved buried contact (LGBC) solar cell technology is proving to be an attractive method of producing solar cells that are designed to operate at one sun and at concentration. Such technology is commercially available at Narec for applications at up to 100 suns. Although LGBC cells can have a higher efficiency at one sun when compared with standard non-selective emitter screen-printed solar cells, a more complex manufacturing process is required for these cells. This paper outlines the approach taken under the FP6 EU funded project “Lab2Line”, in which screen-printing and LGBC solar cell processing techniques are hybridized in order to produce lower cost, high efficiency solar cells.
The recent 30% decline in module market prices is the most telling sign of a need for continuous reductions in PV production costs. With this in mind, the cost efficiency of production processes is, next to stable product quality, a vital objective in the planning of production facilities. In this paper, the lessons learned in the area of cost of ownership (COO) forecasting methodologies will be analyzed and evaluated for their potential application to investment decisions in the PV industry. This paper will analyze the cost structure of the PV industry with the aim of underlining the importance of a systematic cost-of-ownership approach.
A major challenge for the solar industry over the next few years is the reduction of production costs on the road to grid parity. Capacity must be increased in order to leverage scaling effects, production and cell efficiency must also be enhanced, and the industry must focus on intensified process optimization and quality control. Laser marking can make a key contribution to fulfilling these requirements. As hard physical coding, laser marking is applied to the raw wafer at the start of the manufacturing process, making each solar cell traceable along the entire value chain and over its whole lifetime. This paper presents Q-Cells’ laser-supported process for coding each individual solar cell (European patent pending), which will require transition work at the laboratory stage before the company’s innovation is ready for mass production.
The U.S. solar PV market is suffering not from a lack of demand or high prices, but rather from an inconsistent labyrinth of rules and regulations which complicate and prolong uptake. There is significant pent-up demand in the U.S. among developers and especially manufacturers; there is not, however, a commensurate regulatory framework that will enable and encourage this demand to be realized. The U.S. political landscape is deeply divided, and policies that would directly or indirectly effect solar demand are no different from any other in this regard.
The minority carrier lifetime is a key parameter for the performance of solar cells as it characterizes the electrical quality of the semiconductor material. Consequently, accurate and reliable methods to determine the minority carrier lifetime are of enormous interest for both practical process control and the evaluation of the potential and limitations of a specific cell concept. Due to its importance, many different lifetime measurement techniques have been developed and used over the past few decades. This paper aims to present and discuss the most common measurement methods on the one hand, while attempting to shed light on some recent developments on the other. The determination of the minority carrier lifetime of crystalline silicon thin-film (cSiTF) material is illustrated as an example of interest for those who are already familiar with standard lifetime characterization.
