Ribbon technology

String ribbon technology, 23 41 Strip copper, 7 693, 724 Stripped bass... 

To understand the potential of the different photovoltaic silicon ribbon technologies, a closer look at the wafer growth technology, wafer characteristics and behaviour in the cell process are all necessary. 

Fig. 7.1. Classification of silicon ribbon technologies according to the shape of the meniscus at the liquid-solid interface [22]. For Ml, the lower part of the meniscus is formed, e.g. by a shaping die, whereas M2 has a broad base at the free surface of the liquid. Both Ml and M2 represent ribbon techniques, where the crystallisation front moves in the direction of ribbon transport (type I). M3 is characterised by a large liquid-solid interface and represents the techniques with wafer transport almost perpendicular to the crystal growth direction (type II)...

Similar to EFG, an afterheater construction around the crystallisation area is used to reduce thermal stress [29]. As for EFG material, the string ribbon technology uses a small silicon melt crucible in combination with continuous melt replenishment. To overcome the limited throughput of only one ribbon per furnace, compared to 8 or 12 ribbons for EFG, two ribbons [33] and even four with new crucible design [34] can be grown simultaneously in one furnace. The ribbon is cut into 8 x 15 cm2 wafers. 

Similar to the other ribbon technologies, RGS material is rich in carbon concentration due to the refractory materials used and, nowadays, low in oxygen concentration. 

Apart from crystallisation conditions, the materials that are used in ribbon growth equipment and the atmospheric environment are important factors that influence the wafer characteristics. In most of the ribbon technologies, the solidification area is in close proximity to refractory materials, such as the shaping die in EFG or the casting frame and substrate in RGS. In contrast to... 

Staple and Tow. The same extmsion technology that produces continuous filament yam also produces staple and tow. The principal difference is that spinnerets with more holes are used, and instead of winding the output of each spinneret on an individual package, the filaments from a number of spinnerets are gathered together into a ribbon-like strand, or tow. A mechanical device uniformly plaits the tow into a carton from which it can be continuously withdrawn without tangling. 

Using rapid solidification technology molten metal is quench cast at a cooling rate up to 10 °C/s as a continuous ribbon. This ribbon is subsequently pulverized to an amorphous powder. RST powders include aluminum alloys, nickel-based superalloys, and nanoscale powders. RST conditions can also exist in powder atomization. 

In the early 1970s, the first companies to apply low cost, mass production techniques to photovoltaics, a technology that had previously been considered an exotic aerospace technology, emerged. These techniques included the use of electroplated and screen printed metal paste electrical conductors, reflow soldered ribbon interconnects, and by 1977, low cost, automobile windshield-style, laminated module constmction. Such processes benefitted from a substantial existing industrial infrastmcture, and have become virtually ubiquitous in the present PV industry. 

A second method grows siUcon ribbons or sheets dkecfly, bypassing the ingot stage. The sheets ate cut into ceU-size pieces that ate processed to make cells. This manufacturing approach consumes less siUcon than ingot-based technologies. 

For technological applications it is highly desirable to be able to design self-assembling systems to have particular physico-chemical properties under a given set of experimental conditions. Using computer simulation, it is possible to construct an atomistic model of tapes, ribbons and fibrils to study all of the interatomic interactions within the system in a quantitative manner. Figure 13 shows atomistic... 

This step is evidently not required for ribbons, apart from edge trimming and cutting the wafers from the sheets. This is considered to be a major advantage over ingot technology in terms of costs. 

In 1996, a 50 m underground superconducting cable (wound from 6 km of a BSCCO ribbon) and a 150 kW superconducting electric motor were successfully demonstrated. Further development of practical superconductor devices might well depend more on the development of suitable refrigeration technology than on the preparation of new superconducting materials. 

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