Influence of Polymer Gate Dielectric on Organic Field‐Effect Transistors: Interdependence of Molecular Weight, Solvent Polarity, and Surface Energy—A Case Study with PMMA and Pentacene

Abstract

The semiconductor/dielectric interface controls the performance of organic field-effect transistors (OFETs). Herein, the influence of both the molecular weight and the polarity of the solvent of a poly(methyl methacrylate) (PMMA)-based gate dielectric on the performance of pentacene OFETs is systematically investigated, by studying surface energy, surface roughness, morphology, leakage current, and capacitance of the dielectric. Various existing views on the role of the surface energy are considered while deriving a correlation. Larger pentacene grains are observed when the film is grown on high molecular weight-PMMA films cast from high dipole moment-solvent. The electrical properties of the corresponding OFETs show great improvement compared to those of OFETs fabricated with low molecular weight-PMMA film as the gate dielectric, irrespective of the solvent. The authors attribute this enhanced performance to the increased surface energy of the polymeric dielectric which turns out to be a strong function of its molecular weight and the dipole moment of the solvent. Bias-stress measurements on the OFETs confirm this correlation.

Amorphous Fluorinated Acrylate Polymer Dielectrics for Flexible Transistors and Logic Gates with High Operational Stability

“…Organic thin-film transistors (OTFTs) have gained significant attention owing to their applications in flexible display, radio frequency identification, and various types of sensing applications. − Various studies on enhancing the electrical performance of OTFTs for the abovementioned applications have been reported. − One such studies is improving the properties of gate insulators. Gate insulators play a critical role in the operation behavior of OTFTs, such as undesirable leakage charge flow and bias-stress stability characteristics. − In addition, in the case of the most common top-contact OTFT, the morphological properties of the organic semiconductor (OSC) can be influenced by the surface properties of gate insulators, which are directly related to the charge transport characteristics of OTFTs. − Therefore, developing appropriate insulating materials showing suitable characteristics for high-performance OTFTs is a very significant part in the realization of OTFTs utilized in next-generation electronics.…”