The future of solar panels: thin, cheap, safe

A collaborative effort between Oregon State University researchers and Colorado's National Renewable Energy Laboratory has discovered a new material that could potentially be used to construct cheaper and safer solar panels.  

The photovoltaic, or PV cell, is an individual light collector on the solar panel that would use a crystalline sheet composed of iron, sulfur and silicon or germanium to absorb sunlight and generate electricity. It is possible for these sheets to be constructed of much thinner layers than previous absorbers.  

Additionally, the materials themselves would be cheap.  

"Iron, silicon and sulfur are maybe the three least expensive elements in terms of their cost and availability," said Douglas Keszler, a distinguished professor of inorganic chemistry at OSU and the director of the Center for Green Materials Chemistry.

The research stemmed from investigation of iron pyrite, commonly called Fool's Gold, which was once seen as having high potential for capturing energy from the sun.  However, when the iron-sulfur crystalline panels were created and tested, they performed far lower than projected.  

Now, these researchers have performed tests that show that the iron-sulfur crystal sheets separate into two different "phases," one of which consists of an imperfect crystal with less sulfur.  This greatly decreases the crystal's ability to absorb sunlight.  

But researchers have found a potential solution.  

"Theoreticians at NREL select materials from the periodic table and run a large computation specifically looking for properties that are attractive for solar cells," said Ram Ravichandran, an electrical engineering student and co-author of the study. "The chemistry department fabricates powders and single crystals of the compounds to verify the theoreticians' calculations."

He added, "We in the electrical engineering department collaborate with the chemistry department to fabricate thin films of the said compounds to verify results obtained by the chemists as well as the theoreticians."

NREL computations indicated that the addition of silicon or germanium to the absorber's crystal structure would stabilize the absorber during its creation and prevent phase separation from occurring.

When OSU researchers included the silicon or germanium in the thin crystal sheets, no phase separation occurred and early tests indicated that they retained the properties that theoretically make them ideal candidates for constructing solar cells.  

One important property of a solar collector is having the correct "band gap," or energy required to conduct electricity.  These new iron-sulfur-silicon/germanium materials have a calculated band gap of 1.3-1.5 electron volts, which should theoretically allow them to absorb the most sunlight.  

The next step would be to construct working solar cells that utilize these crystal sheets and measuring whether it performs as projected.  

"Now is where the work begins," Ravichandran said.  "Since we've identified this as a new potential material for photovoltaics, it will be interesting to see if we can integrate this material in a thin film solar cell structure to demonstrate how this new material behaves. We are also working to identify and synthesize other new materials that can be alternatives to current thin film solar cell absorbers."