Semiconductor materials[i],[ii] used in the manufacture of photovoltaic (PV) cells are classified as either crystalline silicon or thin-film. About 80 percent of all manufactured PV cells are crystalline silcon (c-Si) which are more efficient, more costly than thin-film. Most of the remaining 20 percent PV cells are made of thin-film cadmium telluride (CdTe), amorphous silicon (a-Si), or copper indium gallium selenide (CIGS), and thin-film is gaining in popularity due to its cost. A cross between c-Si and thin film is referred to as a hybrid.
According to Quantum Solar Power, crystalline silicon cells are 15 to 20 percent efficient, and thin film is 6 to 11 percent efficiency. The crystalline silicon PV cells, the thickness of a human hair, are more durable and more expensive. The thin film PV cells are considerably thinner and less expensive. The hybrid, crystalline silicon and thin film, has an efficiency of 18 to 30 percent and is more expensive than the others PV materials separately.
According to EvoEnergy, monocrystalline silicon cells are 0.2 to 0.3 millimeters (mm) thick and have an efficiency of 13 to 17 percent, and polycrystalline-Si cells are 0.3 mm thick and have an efficiency of 11 to 15 percent. Amorphous silicon (a-Si), a thin film PV cell, is 0.0005 to 0.002 mm thick and has an efficiency of 6 to 8 percent. A hybrid PV, comprised of monocrystalline-Si PV and ultra-thin a-Si, has efficiency in excess of 18 percent.
The promise of thin-film cost containment, however, is not without its issues. The least costly a-Si PV is generally used for small scale pocket calculators and other home devices, not considered a viable stand-alone solar panel contributor. On the other hand, CdTe thin-cell PV is being used with greater frequency in photovoltaic power facilities worldwide.
Presently, U.S. First Solar is the market leader of CdTe PV, and there are rumbings regarding its financial distress.[iii] There are suggestions that First Solar can not compete monetarily with China not only due to the cost of labor disparity between the U.S. and China labor force, but the U.S. has limited access to tellurium-rich ores. The Mother Load of Tellurium-rich Ores has been discovered in and is being mined in China. Until the U.S. or Europe can access other resources of tellurium, the Chinese will be able to corner the market, limit access and raise cost for other countries.
Another issue that has come to light in CdTe PV is cadmium toxicity. Toxic metal recycling costs are a hidden expense on top of the manufacturing costs. The commercial units are sandwiched between glass and do not have the added concern that plastic laminated residential units have during a fire—the release of the toxic metal cadmium into the environment.[iv]
Nipping at the heals of CdTe PV cells is a recent material development—copper-indium-gallium-selenide. CIGS is the most efficient of the thin-film materials. It is flexible and light weight, and it is relatively inexpensive. Sounds great! Yet, CIGS is having a hard time getting off the ground. Why? The CIGS PV manufacturers are viewed as a pariah by financial institutions and unable to obtain venture capital—guilty by association. Solyndra (after developing and manufacturing proprietary, rolled CIGS tube PV) declared bankruptcy shortly after accepting over $500,000,000 in U.S. Federal Funds from the Department of Energy. The tax payers lost all, and venture capital funding dried up—the “Solyndra Fear Factor.” Solyndra claimed they could not compete, once again, with China. Cost containment by U.S. manufacturers had been a pipe dream! And it was never clear that the CIGS PV that was manufactured by Solyndra actually worked. When Solyndra filled for bankruptcy, they proceeded to destroy all their CIGS panels. If the panels had been as efficient as they claimed, why did they not sell them for whatever pittance the market would bear instead of tossing them in the trash. Something smells rotten!
[i] Quantum Solar Power: A Comparison of PV Technologies. Review at–www.quantumsp.com/en/solar-energy/a-comparison-of-pv-technologies/
[iii] Brian Coppa: The Rise and Fall of First Solar: what it means for solar industry. (Feb. 14, 2012) Reviewed at—www.examiner.com/green-business-in-phoenix/the-rise-and-fall-of-first-solar-what-it-means-for-solar-industry/
[iv] Cadmium telluride photovoltaics. en.wikiedia.org/wiki/Cadmium_telluride_photovoltaics/