Effect of Alkyl-Chain Length on Charge Transport Properties of Organic Semiconductors and Organic Field-Effect Transistors

The molecular structure and electrical properties of two n-type organic small molecules which have the same core but different alkyl chains are compared. The effect of the length of alkyl chains on charge transport along the alkyl-chain stacking direction (out-of-plane) is investigated by a combination of techniques. The results show that a longer alkyl chain corresponds to lower out-of-plane mobility (mu(out-of-plane)). More importantly, it is found that this effect not only plays a significant role in affecting the performance of diode-structure devices such as organic light-emitting diodes (OLEDs) or organic photovoltaics (OPVs), but also has profound influence on the performance of organic field-effect transistors (OFETs), especially for OFETs which are in staggered configuration.