Edinburgh Instruments Ltd

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Determination of Chromaticity Coordinates and Bandgaps of III-V LEDs Using Electroluminescence Spectroscopy

In 1907 English engineer Henry Joseph Round was testing the rectifying current behaviour of SiC crystallites and noticed that a faint yellow light was emitted from the SiC; this was simultaneously the first reported observation of the phenomena of electroluminescence spectroscopy and the first successful operation of a light emitting diode (LED). The work of Round was expanded on by a few others in the early 20th century, but it would take many decades for LEDs to become efficient enough for practical use.

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Excitation-emission spectroscopy with charge coupled detectors

Excitation-emission spectroscopy becomes increasingly useful in the study of photo-luminescent materials. The spectral selectivity of the technique enables the quantification of multiple emitting sites in rare-earth doped crystals as well as the rapid acquisition of polycyclic aromatic hydrocarbons (PAH) in contaminated water. In order to obtain a complete spectral fingerprint via excitation-emission spectroscopy, scans at multiple excitation wavelengths over the emission spectra are required. Especially in the case of rare-earth materials with narrow emission linewidths, this is extremely demanding in terms of resolution. The acquisition time of such excitation-emission maps (EEM) can be significantly reduced by using Charge Coupled Device (CCD) detectors.