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Photoluminescence Spectroscopy

Photoluminescence (PL) spectroscopy is a contactless, nondestructive method to probe the electronic structure of materials. Our capabilities include: various excitation wavelengths that allow for varying levels of volume excitation; a detection range extending from 0.4 to 2.7 µm; sample temperatures of 4 to 300 K; and mapping capabilities with 1- to 2-µm spatial resolution on the Fourier-transform-based system.

The intensity and spectral content of the emitted photoluminescence is a direct measure of various important material properties, including:

Image of three-dimensional map produced by Fourier transform photoluminescence microspectroscopy.

NREL researchers use scanning Fourier transform photoluminescence microspectroscopy to produce three-dimensional maps to determine the composition and quality of grown absorber materials

Bandgap Determination. The spectral distribution of PL from a semiconductor can be analyzed to nondestructively determine the electronic bandgap. This provides a means to quantify the elemental composition of compound semiconductor and is a vitally important material parameter influencing solar cell device efficiency.

Impurity Levels and Defect Detection. The PL spectrum at low sample temperatures often reveals spectral peaks associated with impurities contained within the host material. The high sensitivity of this technique provides the potential to identify extremely low concentrations of intentional and unintentional impurities that can strongly affect material quality and device performance.

Recombination Mechanisms. The quantity of PL emitted from a material is directly related to the relative amount of radiative and nonradiative recombination rates. Nonradiative rates are typically associated with impurities and thus, this technique can qualitatively monitor changes in material quality as a function of growth and processing conditions.

For additional information contact Dean Levi, 303-384-6605.