Researchers have revealed the fundamental aspect of a new approach to growing InGaN crystals for diodes, which promises to move photovoltaic solar cell technology toward record-breaking efficiencies.
Solar energy crystallizes
The InGaN crystals are grown as layers in a sandwich-like arrangement on sapphire substrates. Typically, researchers have found that the atomic separation of the layers varies; a condition that can lead to high levels of strain, breakdowns in growth and fluctuations in the alloy’s chemical composition.
Pulses of molecules were introduced to achieve the desired alloy composition. The method, developed by Doolittle, is called metal-modulated epitaxy. “This technique allows an atomic, layer-by-layer growth of the material,” says Ponce.
The elimination of two seemingly insurmountable defects (non-uniform composition and mismatched lattice alignment) ultimately means that LEDs and solar photovoltaic products can now be developed that have much higher, efficient performance.
Photo by: Arizona State University
“While we are still a ways off from record-setting solar cells, this breakthrough could have immediate and lasting impact on light emitting devices and could potentially make the second most abundant semiconductor family, III-Nitrides, a real player in the solar cell field,” says Doolittle. Doolittle’s team at Georgia Tech's School of Electrical and Computer Engineering also included Michael Moseley and Brendan Gunning. A patent is pending for the new technology.
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