7

Charge Transport Physics of High-Mobility Molecular Semiconductors

Henning Sirringhaus, Tomo Sakanoue, and Jui-Fen Chang

7.1 Introduction

There has been tremendous progress in discovering new classes of organic semiconductors that provide field-effect mobilities μ above 1 cm2/(V s) and allow addressing increasingly demanding thin-film electronic applications [1]. For many years, the performance of organic field-effect transistors (OFETs) seemed to be inherently lower than that of their inorganic counterparts, in particular, compared to amorphous silicon (a-Si) and polycrystalline FETs that have characteristic mobilities on the order of 0.5–1 and 100 cm2/(V s), respectively. Due to extensive materials development and evaluation of different classes of organic semiconductors, there is now a broad range of organic semiconductors, both vacuum and solution processable, as well as small molecule and conjugated polymer based, which are able to reach mobility values exceeding that of a-Si. The processing characteristics of these materials make them suitable for applications that cannot be easily addressed by many inorganic materials. Organic semiconductors are inherently low-temperature materials. Because of the absence of covalent bonding between molecules, they can be processed at temperatures below typically 100–150 °C from either vapor phase or solution into high-quality thin films that exhibit a low density of electronic defects. This makes them suitable for applications with a ...

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