On the stability of organic field-effect transistor materials

Stability and degradation of transistor performance of devices based on pentacene and α-sexithiophene are investigated. In order to distinguish between effects at grain boundaries and material issues, macroscopic bicrystals were used, where transistors were prepared on a single grain as well as across a single grain boundary. The main reason for performance instabilities is the formation of oxygen-related trapping states at the grain boundary upon exposure to air. However, especially in the case of pentacene, stable hole transport properties are observed.