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 (µout‐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.