Le Invenzioni Essay

1886 Words Apr 8th, 2014 8 Pages
MSE 542 – Final Term Paper Title: Organic Semiconductor for Flexible Electronics Name: Chunhung Huang

Introduction: An organic semiconductor is an organic compound that possesses similar properties to inorganic semiconductors with hole and electron conduction layer and a band gap.4 Organic semiconductors differ from other organic material in that the molecules that they are made of have π conjugate bonds which allow electrons to move via π-electron cloud overlaps. Conduction mechanisms for organic semiconductor are mainly through tunneling, hopping between localized states, mobility gaps, and phononassisted hopping.5 Like inorganic semiconductors, organic semiconductors can be doped in order to change its conductivity. Although
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3 As a result of this limitation, organic semiconductors are not suitable for use in electronic applications that require very high switching speeds. However, the performance of some organic semiconductors, coupled with their ease of processing makes it competitive in electronic applications that do not require high switching speed such as amorphous silicon used for TFT-LCD.

Main Body: Organics semiconductors are possible because carbon atoms can form sp2hybridisations where the sp2-orbitals form within a plane and the pz orbitals are in the plane perpendicular to it. 4 For organic molecules, a σ -bond between two carbons are formed by creating an orbital overlap of two sp2-orbitals (Figure 1). This creates a large energy difference between the occupied binding orbitals and the unoccupied anti-binding orbitals. This large energy difference leads to insulating properties, and thus longer chains of carbon atoms would have a larger gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). However, in sp2hybridisation, the pz orbitals form additional π -bonds. These bonds have much smaller energetic difference between the HOMO and LUMO, leading to semiconducting properties.

Figure 1 Organic semiconductors can be divided into two types, short chain (oligomers) and long chain (polymers).5Typical examples for semiconducting

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