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Friday, 26 November 2010

Light Emitting Polymer

The seminar is about polymers that can emit light when a voltage is applied to it. The structure comprises of a thin film of semiconducting polymer sandwiched between two electrodes (cathode and anode).When electrons and holes are injected from the electrodes, the recombination of these charge carriers takes place, which leads to emission of light .The band gap, ie. The energy difference between valence band and conduction band determines the wavelength (colour) of the emitted light.

They are usually made by ink jet printing process. In this method red green and blue polymer solutions are jetted into well defined areas on the substrate. This is because, PLEDs are soluble in common organic solvents like toluene and xylene .The film thickness uniformity is obtained by multi-passing (slow) is by heads with drive per nozzle technology .The pixels are controlled by using active or passive matrix.

It is a polymer that emits light when a voltage is applied to it. The structure comprises a thin-film of semiconducting polymer sandwiched between two electrodes (anode and cathode) as shown in fig.1. When electrons and holes are injected from the electrodes, the recombination of these charge carriers takes place, which leads to emission of light that escapes through glass substrate. The bandgap, i.e. energy difference between valence band and conduction band of the semiconducting polymer determines the wavelength (colour) of the emitted light.

The advantages include low cost, small size, no viewing angle restrictions, low power requirement, biodegradability etc. They are poised to replace LCDs used in laptops and CRTs used in desktop computers today.
Their future applications include flexible displays which can be folded, wearable displays with interactive features, camouflage etc.

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