The Second Coming of CIGS

Jim Paull for Zondits

More money has been pumped into copper indium galium di-selenide (CIGS) solar cells than any other photovoltaic (PV) technology. Less than a decade ago, CIGS was thought to be the heir to the future of PV: inexpensive materials only nanometers thick, deposited on glass or stainless steel foil. The “roll-to-roll” notion was bandied about, creating an analogy to high-speed printing processes. And the theoretical efficiency of CIGS is almost as good as that of silicon PV cells. So it’s no wonder that less than a decade ago, billions of dollars were invested in CIGS companies, almost all of them in the US.

But while it’s relatively easy to make a high-efficiency 1-square centimeter CIGS test “coupon,” it proved nearly impossible to replicate that on a slab of glass or a foot-wide web of stainless foil. High efficiency could only be obtained in small areas or shunts in the cell made for very poor semiconductor performance. Moreover, the CIGS metallic “soup” was vulnerable to degradation by water vapor, making total glass encapsulation the only practical way to make CIGS modules.

global-solar-cigs-foilDespite valiant efforts to solve the manufacturing and reliability issues, one by one the CIGS companies went out of business or were sold at fire sales. (The most notorious of these was Solyndra, a company that had received over a billion dollars in venture investment but still defaulted on a half-billion dollar US government-guaranteed loan.) Many of the struggling CIGS companies were acquired by Hanergy, a Chinese company with no apparent business other than scooping up thin film (mostly CIGS) companies on the ropes, including Solibro, Miasole, and Global Solar. Hanergy was thought to be a company without substance, hyping their technology acquisitions just to inflate its stock price; indeed, just a year ago Hanergy’s CEO, Li Hejun, was the richest person in China (on paper). To date, only Japan’s Solar Frontier has been able to produce a commercially successful CIGS product.

However, behind-the-scenes work on CIGS technology continued in China and the US. When I recently visited SUNY Albany’s College of Nanoscale Science and Engineering (CNSE) thin film research facility at the former factory of defunct CIGS manufacturer Daystar located in Halfmoon, New York, an array of CIGS products from Hanergy’s portfolio and other suppliers were being field tested, and the former Daystar manufacturing equipment was being used to continue to develop and refine CIGS technology.

It appears that the most pressing technical issues – efficiency and moisture degradation – are being solved, and that at least two companies are reentering the marketplace. Both SoloPower and MiaSole are again offering CIGS “modules” based on lightweight foil cells in water-vapor resistant encapsulation. And the companies are taking advantage of their products’ differentiating characteristics; since CIGS are lightweight and flexible, they can be applied to buildings in ways that conventional solar modules cannot.

Venture capital investment in solar – especially in different, promising technologies like CIGS – was at a fever pitch 8 to 9 years ago. Venture capitalists, however, need a return on their investment within a matter of years, not decades, so they have abandoned pursuing most technology investments in solar. But engineers and scientists, unfettered by such time restrictions, have shown that with time and a dogged pursuit of a technology they believe in, they can succeed in the end.

Jim is a Senior Engineer at ERS and CEO of Stellaris Corporation.
Image credit: Stellaris Corporation