Quantum efficiency (QE) – also referred to as Incident Photon to Charge Carrier Efficiency (IPCE) - indicates the ratio of the number of photons incident on a solar cell to the number of generated charge carriers. In order to understand the conversion efficiency as a function of the wavelength of light impingent on the cell, the QE/IPCE measurement is critical for materials research and cell design. With this data, the composition and topography can be modified to optimize conversion over the broadest possible range of wavelengths.

The key to accurately measuring the QE/IPCE of a solar cell is to quantify the intensity of monochromatic light incident to the device under test and measuring how much current is generated. The QEPVSI-b is assembled and tested by Oriel Instruments, an industry leader in light sources and spectroscopy. Oriel provides the expertise to ensure accuracy of the solution's performance. Modulated light from a Xenon source is sent through order sorting filters and into an Oriel Cornerstone™ 260 monochromator to generate a monochromatic light output. The output beam path is then focused to a well-defined area. The monochromator scans over a user-selectable wavelength range with the output focused onto the calibrated silicon reference detector providing the radiometric measurement. A digital lock-in amplifier isolates the signal from background noise for accuracy and repeatability. This process is repeated for the cell under test. Total optical power incident on the detector is compared to the current generated by the cell under test. Instrument control, data collection and calculations are all done through Oriel’s TracQ™ Basic software.