Publication

Splitting of the recombination zone in organic light emitting diodes by dye doping

Abstract

In organic light emitting devices, doping of the electroactive organic layer with highly luminescent molecules has been shown to considerably increase device performance and lifetime. In most cases, the doping molecule does not act as a charge donor or an acceptor as in classical semiconductors, but is used to enhance light emission and to tune the emission color. By using the laser dye derivative 4-(dicyanomethylene)-2-methyl-6-{ 2-[(4-diphenylamino)phenyl]ethyl}-4H-pyran as dopant in a standard organic light emitting device, we have achieved highly efficient red to yellow emission depending on doping concentration. Furthermore the emission color changes with increasing current density. Using device model simulations, we have found that this color change is caused by the splitting of the recombination zone into two zones due to a decrease of the electron mobility inside the doped area

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Related concepts (32)
Light-emitting diode
A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corresponding to the energy of the photons) is determined by the energy required for electrons to cross the band gap of the semiconductor. White light is obtained by using multiple semiconductors or a layer of light-emitting phosphor on the semiconductor device.
OLED
An organic light-emitting diode (OLED), also known as organic electroluminescent (organic EL) diode, is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound that emits light in response to an electric current. This organic layer is situated between two electrodes; typically, at least one of these electrodes is transparent. OLEDs are used to create digital displays in devices such as television screens, computer monitors, and portable systems such as smartphones and handheld game consoles.
Organic semiconductor
Organic semiconductors are solids whose building blocks are pi-bonded molecules or polymers made up by carbon and hydrogen atoms and – at times – heteroatoms such as nitrogen, sulfur and oxygen. They exist in the form of molecular crystals or amorphous thin films. In general, they are electrical insulators, but become semiconducting when charges are either injected from appropriate electrodes, upon doping or by photoexcitation. In molecular crystals the energetic separation between the top of the valence band and the bottom conduction band, i.
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