Labor Campus Golm
M7 – Electroluminescence of Polymers
The recombination of holes and electrons in a luminescent material can produce light. This emitted light is referred to as electroluminescence (EL) and was discovered in organic single crystals in 1963. EL from conjugated polymers was first reported in 1990. Since then, research in the field rapidly progressed to the point of commercial application of organic light-emitting diodes.
EL devices have potential applications in a wide field ranging from multicolor displays to optical information processing. Polymers have the advantage over inorganic and molecular materials in the ease with which thin, structurally robust and large area films can be made from polymer solutions. Using printing techniques, patterned structures can be produced easily. Even flexible displays can be produced because of the good mechanical properties of polymers.
In this lab course, basic optical and electrical properties of conjugated polymers will be investigated. The spectral characterization (photoluminescence and electroluminescence) of polymer-based light emitting diodes (LEDs) will be carried out using a modular spectrometer. The experiment includes the steps necessary for a correction of spectra to eliminate the influence of the equipment. The efficiency of the LEDs has to be determined using the spectral data.
Measure the absorption spectra of your polymers (thin films spin coated onto glass substrates).
Characterize the setup used for luminescence measurements.
Identify possible sources of error and collect data necessary for correction.
Measure the photoluminescence emission spectra for the polymer films in an appropriate measurement geometry, using suitable excitation wavelengths.
Measure the photoluminescence excitation spectra for the polymer films in an appropriate measurement geometry, using suitable detection wavelengths.
Measure the current through the LED and the spectral radiant intensity of electroluminescence as a function of applied voltage (the current-radiance-voltage characteristics).
Measure the electroluminescence emission spectrum at a suitable voltage or current. Measure the radiance of an OLED as a function of viewing angle.
Determine the radiometric and luminous efficiencies of the polymer LEDs