Polymer assisted transferring of patterned electrodes for a weak anisotropic charge transport study in monolayer molecular crystals

Abstract

Monolayer molecular crystals (MMCs) have attracted worldwide research interest due to their unique properties toward their bulk counterparts. The lower contact resistance of MMCs over their bulk counterparts makes them ideal carriers for studying the intrinsic properties of organic semiconductors. Anisotropic charge transport is an important characteristic of organic single crystals and also one of the primary factors induced in device performance fluctuation; however, related studies based on MMCs are still rare. MMC materials with a weak charge transport anisotropic property would be urgently needed and is of great significance for realizing high performance device arrays with low device-to-device variation. The major difficulty regarding anisotropic charge transport study in MMCs lies in the non-destructive preparation of electrodes on MMCs. Here, by taking advantage of the varied adhesion forces between substrates/gold electrodes/polymer films, the prepatterned fan-shaped electrodes could be readily transferred to target MMCs for the anisotropy study. By this non-destructive dry transferring of top electrodes, anisotropic charge transport properties of typical 2,6-bis(4-hexylphenyl) anthracene (C6-DPA) and 1,4-bis((5′-hexyl-2,2′-bithiophen-5-yl)ethynyl)benzene (HTEB) MMCs were obtained with an anisotropic ratio of 1.15 and 2.15, respectively. The low anisotropic ratio of C6-DPA would facilitate the future applications in MMC OFET arrays without considering the influence of crystal orientation.