New technology could spur growth in photovoltaic panels

Researchers at the National Renewable Energy Laboratory (NREL) have surpassed two records in solar cell design, paving the way toward reducing the cost of photovoltaics systems that produce electricity directly from sunlight.

In April, researchers from the National Center for Photovoltaics (NCPV) surpassed a record for electricity produced by solar cells made from cadmium telluride – a development that could help meet expanding demand for solar systems.

The measurement of 16.4 percent efficiency bested the previous threshold of 15.8 percent efficiency for a cadmium telluride cell – a record that has stood since 1992. The efficiency of a solar cell is calculated as the percentage of available sunlight the device converts into electricity.

The record-setting cadmium telluride (CdTe) process developed by NREL is different from previous cells and benefits from a number of new insights in understanding of the operation of these solar cells. The cell uses new materials that interact chemically with the CdTe to improve adhesion, light collection, and electronic properties, NREL researchers reported.

"This technology offers the prospect of getting a better product to customers," said NREL research manager John Benner. "Our industry partners can use this technology in expanding capacity to meet the rapidly mounting demand for PV."

Cadmium telluride represents one of the most promising technologies for thin-film solar cells. In the thin-film manufacturing process, layers of differing electricity-producing materials are applied sequentially to a glass, plastic or steel backing.

Many experts believe thin-film cells are the wave of the future, because thin films use less semiconductor material than earlier, conventional solar panels.

The second record was set by the High Performance Project The program, started earlier this year to help make solar-electric systems more of an everyday source of power, already has achieved its first milestone – setting a new performance record for a promising solar cell technology.

Through the use of concentrators that focus more sunlight onto a solar cell, NCPV researchers reached a peak efficiency of 21.5 percent from a thin-film copper indium gallium diselenide (CIGS) cell.

It is the first time anywhere that a low-cost thin-film solar cell has reached an efficiency level of greater than 20 percent. "We've hit an important target here, one that even a couple years ago would have been considered unimaginable for thin film technology," said Benner. "Having come so early in the High Performance program, it should provide some early benefits to the solar industry and especially, American consumers."

The record-setting CIGS cell involved the first use of concentrators that multiply the energy of sun's rays, allowing the solar panel to produce more electricity. Researchers are particularly encouraged by the results produced by this combination of low-power concentration and CIGS, and anticipate that products introduced in the next several years will incorporate this innovative technology.