We investigate the temporal properties of the fluorescence emitted by such devices after excitation with an ultrashort optical pulse using a novel wide-field method, fluorescence lifetime imaging (FLIM). This has not previously been applied to PLEDs and provides a new technique for studying the processes leading to black spot formation. The FLIM system developed at Imperial College uses an ultrafast time-gated image intensifier based on microchannel plate technology. This (coupled together with a CCD) can stroboscopically record time-gated images of the fluorescence emitted by a sample after pulsed excitation by changing the trigger delay between optical excitation and signal collection by the CCD. The images from the CCD are then analysed computationally pixel-by-pixel using, for instance, a single exponential decay model so that an image of the fluorescence lifetimes can be created on a false colour scale (a FLIM map). PLED defects have also been studied with FLIM, including bubble formation in the polymer layer. The application of fluorescence lifetime imaging provides a novel method to achieve contrast in microscopic studies of the properties of PLEDs and to probe the mechanisms behind defect formation.
Fluorescence lifetime imaging of polymer LEDs
01.01.2003
121589 byte
Aufsatz (Konferenz)
Elektronische Ressource
Englisch
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