By Keira Ray 

When Edmund Becquerel discovered the photovoltaic effect in 1839, he likely never imagined the enormous impact it would one day have on the world. It’s been nearly 200 years since Becquerel’s breakthrough, and in that time the planet has undergone a solar transformation.

In 1954, Bell Laboratories made headlines by demonstrating the practical use of their photovoltaic cell, called the Bell solar battery. The Bell battery was the first practical solar cell and sparked the imagination of the public.1 This first silicon solar cell paved the way for future generations of silicon cells, which have become today’s standard for high-performance solar panels. As with all technologies, solar photovoltaic modules must evolve in order to remain compatible with modern needs and expectations. Thin film solar panels play an important part of that evolutionary growth. But what exactly is thin film solar, and how does it fit into the future of solar technology?

Thin film solar is an alternative to crystalline silicon photovoltaic modules.

The vast majority of installed solar panels are made from silicon,2 just like the Bell solar battery. Most of these silicon panels are made of either polycrystalline or monocrystalline silicon. Monocrystalline panels are the most efficient variety of silicon solar technologies, but they are also generally the most expensive.3 As efficient as crystalline silicon panels are, they are often heavy and cumbersome—this is where thin film panels come into play.

Thin film solar panels, as the name suggests, are much thinner and lighter than either mono- or polycrystalline silicon panels. They are manufactured by applying a thin layer of photovoltaic semiconductors over a contact plate and substrate.4 The resulting thin film cells are highly uniform in appearance, and can be made to be flexible—this means they can be used in a wider range of situations than crystalline solar cells.5 What’s more, thin film panels end up requiring 100 times less material than their crystalline silicon counterparts,6 thereby driving down manufacturing costs.

thin film solar

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Thin film solar technology is catching up to crystalline solar panels.

In the past, thin film technology was not often a practical solution for distributed solar power generation. This type of solar cell has a history of low energy conversion and power output, and therefore requires a much larger array in order to produce enough electricity to power a home. Thin film solar modules are made with a range of photovoltaic materials. The next generation of thin film solar panels, however, is more powerful than ever before and is being developed for a large number of applications.

Thin film solar modules are made from three main semiconducting materials: Amorphous silicon (a-SI), cadmium telluride (CdTe), and copper iridium gallium selenide (CIS/CIGS).7 While other technologies are in development, these three types of modules currently command the market for thin film solar—a market which is expected to reach nearly $21 billion by 2023.8

As far as conversion efficiencies go, CdTe and CIGS modules are both more efficient than amorphous silicon solar cells. Under research conditions, individual CdTe and CIGS solar cells can reach efficiencies of over 22%—that’s even more than some commercially-available crystalline silicon modules.9 10 In comparison, the efficiency rates of the latest a-SI cells are just over 13%—and that’s under ideal laboratory conditions.11

While top-of-the-line thin film solar cells are capable of reaching conversion efficiencies over 20%, the actual output of a thin film array is usually a little lower—this is a phenomenon that’s seen across all solar photovoltaic technologies.12 In actual practice, a thin film array generally converts closer to 12% of useable light into electricity.13 Despite major improvements in recent years, this is still below what’s expected from crystalline silicon arrays—though this paradigm may shift in the future.

  • Record Percent Efficiency Rates by Technology

New thin film technologies may represent the future of solar power generation.

Perovskites have exciting potential for photovoltaics

Researchers around the world are dedicated to discovering more efficient, less expensive solutions for solar power conversion. Some experts believe that these “third generation” thin film solar panels may one day overtake other forms of photovoltaics. Emerging thin film technologies include organic photovoltaic cells, dye-sensitized cells, perovskite cells, and quantum dot photovoltaics14.

Perovskite cells are of particular interest to many researchers. Perovskites have a unique chemical structure that makes them a powerful semiconductor. They’re strong, flexible, lightweight, semi-transparent, and less expensive than silicon.15 Documented efficiency ratings of perovskites have jumped almost 18% in just a decade,16 making it one of the most quickly-improving solar technologies currently in development. There are, however, some issues to overcome before perovskites can be successfully brought to market: Perovskite cells suffer increased degradation rates, and are very sensitive to humid conditions.17

Thin film solar panels have joined the ranks of viable renewable energy solutions.

Renewable energy sources are now as economical to produce as fossil fuels. This is excellent news for the future of sustainable energy—as is the wide variety of solar panel technologies that are being developed. The truth about home solar is that while thin film panels have greatly improved in recent years, silicon solar arrays are still the most cost-effective option for most home solar installations. Tax incentives and rebates won’t be around forever—for homeowners looking to go solar, the best way to take advantage of savings is to stick with crystalline silicon.

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Bibliography

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  11. Zyga, Lisa. “Solar Cell Sets World Record with a Stabilized Efficiency of 13.6%.” Phys.org. Science X Network, 4 June 2015. Web. 22 Feb. 2017.
  12. Gabor, Andrew. Cell-to-Module Gains and Losses in Crystalline Silicon PV. N.p.: Gabor Photovoltaics Consulting LLC, 10 July 2013. PPT.
  13. Biello, David. “Solar Power Lightens Up with Thin-Film Technology.” Scientific American. Nature America, Inc., 25 Apr. 2008. Web. 22 Feb. 2017.
  14. Xiaoxi, He, and Harry Zervos. “Perovskite Photovoltaics 2016-2026: Technologies, Markets, Players.” IDTechEx. IDTechEx, 19 Sept. 2016. Web. 22 Feb. 2017.
  15. David Biello, “Solar Power Lightens Up,” 2008.
  16. Xiaoxi and Zervos, “Perovskite Photovoltaics,” 2016.
  17. Gorgol, Jan. “Effects of Humidity and Moisture Degradation on High Efficiency Perovskite Solar Cells.” Surface Measurement Systems. Surface Measurement Systems Ltd., 30 Apr. 2015. Web. 22 Feb. 2017.

Editor: Kelsey Tollefson

Executive Editor: John Lenker