The Breakthrough Institute

By Chris Knight, Breakthrough Generation Fellow

Mention solar photovoltaics (PV) to a group of energy activists or policy wonks, and you'll elicit several different responses. "It's soooo expensive," will say one person. "Why don't we use more of it?" will be the cry of another. And if you have anyone from California in your group, you'll surely hear "Dude, its hella cool!" Lost among these responses is an understanding of the future potential of the cheapest PV technologies: thin-films.

The many varieties of thin-films are too often discounted as futuristic, or lumped together with their more expensive cousin, crystalline PV. Both responses are highly flawed.

Thin-film PV panels deserve attention because they are strongest where traditional crystalline silicon PV panels are weakest; i.e., they are cheap. The crystalline silicon fabrication process of forming a rod of pure silicon and sawing it into wafers is inherently expensive. Thin-films are usually deposited, not sawed, and they use a fraction of the material used in crystalline panels. In recent years, the energy market has began to understand their potential, and growth rate of thin-films made out of Cadmium Telluride (CdTe) and Cadmium Indium Gallium Diselenide (CIGS) has exploded. Next generation organic and nanotech thin-films promise even greater cost declines.

Current thin-films:

There are multiple varieties of thin-films currently in production that will likely dominate the US, if not the global, PV industry in coming decades. In 2008, Cadmium Telluride thin-film producer First Solar reported record low panel production costs of $1.14/watt, which is about half as much as popular silicon panels. They predict that the power from their panels will be competitive with residential electricity rates by 2010-2012. If accurate, this cost achievement would pave the way for mass deployment of PV on the roofs of buildings as well as in peak shaving applications for utilities.

The low cost leader in current generation thin-film is Silicon Valley's Nanosolar, which uses CIGS panels. Nanosolar's CEO has caused a stir in the industry with his statement that their PV panel costs are $.99/watt. A recent patch of panels they shipped to Germany reportedly had an installed cost of $3/watt, which is nearly 1/3 that of the US average. Their San Jose manufacturing plant is expected to have 430 MW of manufacturing capacity, which would more than double the United State's PV manufacturing capacity

This manufacturing strength speaks to an important point: Compared to Japan, Germany, and China, the US doesn't have much of a PV manufacturing base in crystalline PV. But revolutionarily low cost thin-film firms, such as Nanosolar and First Solar's products, are disproportionately concentrated in the US. If the US continues to transfer the knowledge of its high tech regions into thin-film PV manufacturing capacity, these firms could create tens of thousands of American jobs--and add billions to US GDP-- in the 21st century.

Next generation thin-films:

If you think that current generation thin-films are impressive, just wait a decade. Organic PV systems are just around the corner. Organic PV is the easiest of all PV to manufacture because they can be "spin-cast." The organic molecules are dissolved into a solution and then sprayed onto the substrate. Additionally, the organic compounds themselves are cheap, cheaper than either silicon or any of the materials in the current generation thin-films like Cadmium or Tellurium.

The downside of organics at the current state-of-the-art is efficiency. In 2008, the highest efficiencies of such cells are under 5%, contrasted to the 10-20% in the more mainstream technologies. The organics are in a place where the current thin-films were in the 1980s. Therefore, even given the thrift of making them, their efficiencies are simply not high enough to generate a high value product. The outlook, however, is far brighter. According to one Stanford Professor I recently talked with, researchers know what they have to do to get up to efficiencies of 20%, It is merely a matter of time and funding.

If the organics were able to get to higher efficiencies, they could fundamentally change the way we think about solar PV power. The Massachusetts organic PV firm Konarka uses a partially reconfigured label maker to print their organic PV cells. These "power plastics" are flexible and extremely low volume. As such, they can be integrated into a variety of products, including potentially cell phones and laptop computers.

Other contenders in the next-generation PV market use nanotechnology. Bloo Solar, founded by Univesity of California - Davis MBA students and researchers, is trying to exploit the light-trapping potential of nanorods in a solar photovoltaic cell. The use of rod-ends arranged like brush bristles increases the effective surface area of the solar cell, and these rods can be used with any material, from silicon to CIGS.

The Bottom Line:

These promising current and next generation thin-film technologies are an important part of the US response to the energy challenge. PV generated electricity is increasingly cost-competitive, and, with smart deployment policies and increased quantities manufactured, will become even more so. But the success of PV cannot be left to chance. Cost effective applications of current thin-films as part of Roof Integrated Photovoltaic systems need to be exploited through Zero Energy home standards. R&D funding is needed so that organic PV modules can achieve suitable efficiencies. Federal-level standards and subsidies are needed to ensure that, in the end, it won't only be Californians that think solar panels are hella cool.