A Californian firm is set to build the world’s largest solar cell fabrication plant.

Nanosolar, which was seed-financed by the founders of Internet search engine Google, plans to build a volume cell production factory with a total annual cell output of 430MW once fully built, or around 200 million cells per year.

Already in pilot production in Palo Alto, Nanosolar claimed to have started ordering volume production equipment for the 430MW plant. Its first cell fab will be located in California, but its first panel fab “is expected to be located in Berlin, Germany”.

The firm, which has secured a total of $100m funding to date, has spent four years working on a photovoltaic (PV) cell that can be made cheaply by thin-film printing on reel-to-reel equipment without vacuum processing.

“Thin-film printing overcomes the complexity, high cost, and yield and scalability limitations associated with vacuum-based processes,” said the company’s technology head, Chris Eberspacher. “This allows us to produce cells very inexpensively and assemble them into panels that are comparable in efficiency to that of high-volume silicon-based PV panels.”

The technology is copper-indium-gallium-diselenide (Cu (In,Ga)Se2), known as CIGS.

To avoid vacuum processing, Nanosolar uses inks containing particles of CIGS to print the cell absorption layer.

Much of the firm’s technology is still under wraps. For example most CIGS cells use a vacuum-deposited zinc oxide top electrode, but it claims to have a printable one. Nanosolar said it had developed a way of producing transparent electrodes in a way that “enables large-area cells to have very marginal power loss”.

It also claims to have a flexible substrate “an entire order of magnitude less expensive than stainless steel” - the substrate of choice for vacuum-processed reel-to-reel CIGS cells.

Nanosolar