It's like CIGS without the indium, according to Thomas Badegruber.

Crystalsol, a startup from Estonia, will try to commercially release copper tin zinc sulfur and selenium (CZTSS) solar cells in a few years, says Badegruber, the company's managing director. (Badegruber spoke at Nordic Green II last week.)

The company's CZTSS cells can be printed on a flexible substrate. Thus, Crystalsol will aim to get the material incorporated into membrane roofing and other building products.

CZTSS is one of the older, and more obscure, solar materials. Both Philips, the industrial giant, and the Soviet Union, a large country that went out of business 19 years ago, worked on CZTSS cells back in the '60s. That's a micrograph of Crystalsol's material in the photo.

The solar industry, however, coalesced around crystalline silicon and amorphous silicon solar panels. First Solar turned cadmium telluride thin-film solar from a novel oddity to a multibillion dollar business. Miasole, Solyndra, Global Solar and a few others have begun to sell copper indium gallium selenide (CIGS) solar cells.

CTZSS, though, has made a comeback. Earlier this year, IBM showed off an experimental CTZSS cell with a 9.6-percent efficiency. The efficiency gains came from a process devised by IBM that involved embedding the selenide and sulfur into a film as part of the manufacturing process.

The key to CTZSS cells is that they don't contain indium, an element that many believe will rise in price as supplies become tight. You also don't have the problems of recycling and disposal that come with cadmium.

Still, CTZSS has a long way to go. Crystalsol's experimental cells only exhibit around a 6-percent efficiency; the company hopes to get to 11 percent. CIGS companies now produce commercial cells in the 10-percent-plus efficiency range.