“Knitting up” the inter-dipole gaps in dielectric surfaces: an efficient route for high performance organic field-effect transistors

Abstract

Suberoyl chloride (SCL) or ethylenediaminetetraacetic dianhydride (EDT) was added as crosslinking agents into the high-k cyanoethyl pullulan (CEP) polymer and the mixture was cured at temperatures of 90–120 °C. In the crosslinking reaction of the CEP polymer chain with SCL, ester groups were produced to knit up the gaps between the self-associated dipole clusters. Well-stacked pentacene molecular clusters were formed on the dipole clusters and 2-dimensional (2D) layer-by layer growth of the pentacene layer was observed. On the other hand, the dangling carboxylic acid (COOH) group in EDT-cured dielectrics disrupted the quasi-order by shielding the dipoles. This caused discontinuous 3D pentacene grains, which degraded the pentacene organic field effect transistor performance. A high field-effect mobility of ∼8.62 cm² V⁻¹ s⁻¹, an on/off current ratio (I_on/I_off) of ∼10⁵ and a steep subthreshold slope (SS) of 0.099 V dec⁻¹ were obtained using SCL as a cross-linking agent.