Crystalline silicon dominates today’s photovoltaic (PV) industry, with panels being installed at high rates on rooftops and as solar farms. But the fast expansion of the silicon PV market has driven up the costs of materials in recent years, and manufacturing and installation procedures are inherently inefficient and expensive. Because of such limits, it’s been taken for granted in the industry that silicon will be but a passing phase and that wide adoption of solar electricity will depend on the development of thin-film PV materials, which are cheaper to make and apply.
Lately, it’s First Solar that has captured most of the headlines in second-generation PV, with a cadmium telluride thin film that the company says it can make for less than a dollar per watt. Because of First Solar’s breakthrough and other promising developments in both organic and inorganic PV materials, thin films could account for 31 percent of the solar market by 2013, double the 2008 share, according to the analysis firm iSuppli Corp., in El Segundo, Calif.
By comparison with silicon, for a given number of photons from the sun converted into electrons, thin films use only a hundredth the amount of PV material. Because such materials can be printed and rolled, they are particularly suitable for use in building-integrated applications, permitting the production and consumption of electricity on location, thereby saving on transmission and distribution costs.
Copper indium gallium selenide (CIGS), because of its somewhat higher efficiency and because CIGS variants can be tailored to applications, is an attractive alternative to CadTel: As most of the incident photons are absorbed in the top one or two micrometers of the material’s surface, three U.S. cents’ worth of CIGS could replace a dollar’s worth of silicon for an equivalent amount of electricity output. So far, however, CIGS has lacked a reliable and rapid manufacturing process that could scale effectively. This is where our start-up company, HelioVolt, comes in. Working in collaboration with researchers at the National Renewable Energy Laboratory in Golden, Colo., we have devised an innovative manufacturing process that we call FASST, for Field Assisted Simultaneous Synthesis and Transfer. This fall we have started to commercialize the process with a production line at our factory in Austin, Texas.
Relying on the use of precursor materials, FASST enables us to closely control the ratios of the four kinds of atoms that make up the grains of which CIGS consists. Once present in the right proportions, the constituent parts are heated rapidly to coalesce into high-quality, high-efficiency material, with little loss. In essence, FASST provides a way to make thin-film PV materials of high quality and efficiency, faster and more economically than competing processes.