2011 R&D 100 Winner
NREL Flash-QEQuantum efficiency (QE) measurements are valuable for understanding device physics and materials properties of solar cells. QE measurements indicate how well a solar cell converts the various wavelengths of sunlight into electricity (specifically, photons into electrons). A spectral response plot can reveal material bandgaps and thicknesses in solar cells, minority-carrier diffusion lengths, spectral dependence of short-circuit current, and qualitative spatial electronic behavior within cells. These are all important factors in solar cell development.

The Flash Quantum Efficiency System for Solar Cells, developed by the National Renewable Energy Laboratory, Golden, Colo., and Tau Science Corp., Beaverton, Ore., supplies these QE diagnostics at a rate of one second per cell, or more than 1,000 times faster than conventional QE systems. Conventional measurement systems typically rely on a mechanically driven spectrometer that needs 20 min to generate a QE plot. The Flash QE system uses an electronically controlled full-spectrum light source composed of an array of light-emitting diodes (LEDs), with each LED emitting a different wavelength of light. The LEDs illuminate the cell simultaneously—a parallel or simultaneous approachrather than the serial approach of a conventional system. Analog voltage signals are converted to digital voltage signals and processed using Fourier transform algorithms to deliver the spectrum.

This speed boost allows QE measurements to be performed in photovoltaic solar cell manufacturing lines.

Photovoltaic quantum efficiency test system

National Renewable Energy Laboratory
Tau Science Corp.

Development Team

NREL Flash-QE Development Team
(l-r): Paul Stradins, Brian Egaas, David Young from National Renewable Energy Laboratory






The Flash Quantum Efficiency System for Solar Cells Development Team
David Young, Principal Developer, National Renewable Energy Laboratory
Mark Arbore, Tau Science Corp.
Brian Egaas, National Renewable Energy Laboratory
James Hudson, Tau Science Corp.
Greg Horner, Tau Science Corp.
David Klein,Tau Science Corp.
Rommel Noufi, National Renewable Energy Laboratory
John Schmidt, Tau Science Corp.
Paul Stradins, National Renewable Energy Laboratory
Leonid Vasilyev, Tau Science Corp.