High Productivity CIGS Thin Film Turnkey Fab

By Charles Annis – Vice President, Manufacturing Research, DisplaySearch

On August 10, leading German PV equipment supplier Centrotherm Photovoltaics announced it had achieved 13% conversion efficiency for thin film CIGS modules using a patented process at its pilot manufacturing facility. The sample was produced on a small 0.1 m² (300 × 300 mm) substrate, but the company claims that it expects to maintain high efficiency when scaling to larger 1.5 m² (1100 × 1400 mm) glass for mass production turnkey fabs.

This is not such big news in itself. Centrotherm has made multiple previous announcements about its CIGS technology. But it is interesting to note the company is actively promoting is a new, proprietary thin film CIGS turnkey solution at a time when a-Si/µc-Si turnkey customers are seriously concerned about the validity of their business model assumptions.

To date, the vast majority of thin film turnkey lines have been for a-Si/µc-Si solar cells, installed by leading companies such as AMAT, Oerlikon, EPV and ULVAC. According to the DisplaySearch Q3′09 Quarterly PV Cell Capacity Database & Trends Report, the amount of a-Si/µc-Si capacity available for production is increasing rapidly from just 322 MW in 2007 to 1.76 GW in 2009. These four leading a-Si/µc-Si thin film turnkey companies accounted for 80% of that capacity increase. Many of these fabs were purchased by companies with little previous solar cell manufacturing experience looking for a quick and relatively easy way to jump into the PV business. The value proposition for a-Si/µc-Si based solar cells seemed quite positive when silicon was selling for spot prices over $450/kg in early 2008. However, even the best tandem a-Si/µc-Si modules now in production have a conversion efficiency of only around 8.5%. With silicon spot prices now having dropped to $70/kg and still falling, crystalline silicon modules are pushing the conversion efficiency advantage and have become much more cost competitive; now the a-Si/µc-Si turnkey producers find their business models challenged.

Centrotherm is appealing to a similar sort of customer base, but with a new value proposition based on a much more efficient product.

In 2008, only 233 MW of CIGS capacity was available for production and that number could get up to 677 MW by the end of 2009, all of which is from manufacturers like Solyndra and NanoSolar which have their own proprietary, in-house technologies. None of the currently available CIGS capacity is from turnkey lines.

Being a five element compound, it is a technically very difficult to deposit thin film CIGS absorbers with uniform stoichiometry as well as uniform indium and gallium concentrations. The various CIGS components have differing energy band gaps that generate ranging current levels, the lowest of which dominates in a series connected solar cell. For these sorts of reasons CIGS manufacturing is difficult to scale to large areas and tends to suffer from a narrow process window.

With this most recent announcement, Centrotherm is expressing confidence that it can overcome the scaling issues and adopt Gen 5 equivalent glass substrates that will be larger than any of the CIGS modules currently available on the market. Large glass along with the company’s two-step high-throughput selenization process and high conversion efficiency rates mean than Centrotherm may be able to offer a best of class thin film turn-key fab.

As tracked in the DisplaySearch Q3′09 Quarterly PV Cell Capacity Database & Trends Report, Centrotherm has already convinced two customers.