The Physics of Organic Semiconductors: Principles, Transport Mechanisms, and Device Applications
The physics of organic semiconductors begins at the atomic level with the carbon atom. Carbon has an electron configuration of 1s22s22p21 s squared 2 s squared 2 p squared
The electronic structure of organic semiconductors is characterized by a filled valence band and an empty conduction band, similar to inorganic semiconductors. However, the electronic states in organic semiconductors are often described using a molecular orbital (MO) approach, rather than the band structure approach used for inorganic semiconductors. In the MO approach, the electronic states are described in terms of the molecular orbitals of individual molecules or polymer chains. physics of organic semiconductors pdf
This guide outlines the fundamental physics of organic semiconductors—materials primarily based on carbon and hydrogen that exhibit semiconducting properties. Unlike traditional inorganic semiconductors (like silicon), these materials offer mechanical flexibility and tunable electrical properties. 1. Fundamental Nature of Organic Semiconductors
Holes are injected into the HOMO from an anode, and electrons are injected into the LUMO from a cathode. The carriers hop through the organic layers under an applied electric field, meet, form excitons, and radiatively decay to emit light. In the MO approach, the electronic states are
Once generated, excitons move through the organic film during their brief lifetime (nanoseconds for singlets, microseconds for triplets). This migration occurs via two non-radiative energy transfer mechanisms: A long-range (
is the wavefunction decay parameter (degree of localization). rijr sub i j end-sub is the distance between sites. is the energy difference between states ( kBk sub cap B is the Boltzmann constant, and is temperature. In these molecules
Unlike inorganic semiconductors (like Silicon) that rely on a rigid crystal lattice, organic semiconductors are composed of small molecules or long-chain polymers. Their semiconducting nature stems from . In these molecules, carbon atoms undergo sp2s p squared
The variation in energy levels between neighboring molecules. Transfer Integral: How well the -orbitals of adjacent molecules overlap.
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-conjugated systems. This means they have alternating single and double bonds, allowing electrons to delocalize across the molecule.