Polaron
From Biocrawler, the free encyclopedia.
In solid-state physics, a polaron is formed when a moving charge (typically an electron or a hole) in a crystal with some ionic character polarizes (by its electric field) the lattice around it. The resulting lattice polarization acts as a potential well that hinders the movements of the charge, thus decreasing its mobility.
In organic materials, a polaron is formed when a charge within a molecular chain influences the local nuclear geometry, causing an attenuation (or even reversal) of nearby bond alternation amplitudes. This "excited state" possesses an energy level between the lower and upper bands.
The concept of a polaron is used while discussing ways for making a polymer electrically conductive.As an example, PPV (poly paraphenylenevinelyn), is presently the most popular commercially available conducting polymer. In this we try to create an excited state whcih is then eventually relaxed and the energy is emitted either in a radiative manner (emitting light) or a non radiative manner (vibration etc). One of the simplest way to create such an "excited state" i.e. a polaron is by alternating the bond geometry which is done by doping the polymer.
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