Nanometer-Thick Thiophene Monolayers as Templates for the Gas-Phase Epitaxy of Poly(3,4-Ethylenedioxythiophene) Films on Gold: Implications for Organic Electronics

Abstract

Organic electronic devices rely on the performance of polymers that are used as active layers. Poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most studied polymers for organic electronic devices and especially bioelectronics. Because charge carriers move along the polymer backbone (anisotropic charge transport), one of the key challenges is controlling orientation of the polymer in thin films, hence increasing the transport performance. Here, we introduce a method for the oriented growth of PEDOT chains on nanometer-thick self-assembled monolayer (SAM)-modified gold electrodes. We show that, when the gold layer is covered with a SAM that is active for polymer chain growth, a more crystalline film is obtained compared to the surface having a nonactive SAM. We used a nitric acid oxidant to perform the polymerization, which overcomes temperature incompatibility between the gold-supported thiolate monolayers and the polymerization. We characterize the chemical nature and physical properties of the oriented PEDOT film. Reaction conditions and ease of processing appeal especially to organic electronic device applications where surface modification can play a critical role.