Cheaper Solar Cells On The Horizon

workmen installing solar panels
Screening-engineered field-effect photovoltaics — SFPV — will make solar panels easier to produce and lead to wider adoption of solar power.
(cc) Oregon DOT

Solar power from photovoltaic cells has already entered the mainstream. In many communities, it’s not uncommon to see homes, offices, and industrial buildings with rooftop solar panels. Large utility-scale arrays dot the countryside. Now, with technology innovations coming out of the Lawrence Berkeley National Laboratory and the University of California Berkeley, photovoltaic power should soon become more affordable and more widespread.

To date, most photovoltaic cells have been made with semiconductors based on chemically doped large silicon crystals or thin films of copper indium gallium selenide or cadmium telluride. Both the cost of the materials used and the complexities of the manufacturing process make the cells expensive to produce.

A new process, called “screening-engineered field-effect photovoltaics,” or SFPV, is not based on chemical doping. Instead, it uses the nano-scale physical structure of the elements in the cell, along with the electric field effect to control the concentration of charge-carriers, giving the material its semiconductor and photovoltaic properties.

Physicist Alex Zettl, who led the SFPV research, explains how this technology can affect the photovoltaic industry. “Solar technologies today face a cost-to-efficiency trade-off that has slowed widespread implementation. Our technology reduces the cost and complexity of fabricating solar cells and thereby provides what could be an important cost-effective and environmentally friendly alternative that would accelerate the usage of solar energy.”

William Regan, one of the researchers who worked on the new technology, explains, “Our technology requires only electrode and gate deposition, without the need for high-temperature chemical doping, ion implantation, or other expensive or damaging processes. The key to our success is the minimal screening of the gate field which is achieved through geometric structuring of the top electrode. This makes it possible for electrical contact to and carrier modulation of the semiconductor to be performed simultaneously.”

One configuration of SFPV devices requires an external power source, which would contribute to the complexity and cost of the cell. However, a self-gating configuration allows the gate current to come from the cell itself. Regan comments, “The self-gating configuration eliminates the need for an external gate power source, which will simplify the practical implementation of SFPV devices. Additionally, the gate can serve a dual role as an antireflection coating, a feature already common and necessary for high efficiency photovoltaics.”

The advantage of this technology is in that it opens up the range of materials that can be used to produce high-quality devices. Researcher Feng Wang explains, “Our demonstrations show that a stable, electrically contacted p-n junction can be achieved with nearly any semiconductor and any electrode material through the application of a gate field provided that the electrode is appropriately geometrically structured.”

Zettl concludes, “It’s time we put bad materials to good use. Our technology allows us to sidestep the difficulty in chemically tailoring many earth abundant, non-toxic semiconductors and instead tailor these materials simply by applying an electric field.” The result will be cheaper, easier to produce solar cells leading to wider adoption of solar power.

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