Improvement of Field-effect Mobility in Top-gate Organic Field-effect Transistors Using Solution-processed Molybdenum Trioxide Hole Injection Layers

Abstract

Here, we report on the enhancement of field-effect mobility in solution-processed top-gate organic field-effect transistors (OFETs) based on 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C₈-BTBT) using solution-processed molybdenum trioxide (MoO₃) layers. An aqueous solution of MoO₃ was deposited by the spin-coating technique on Au source-drain electrodes fabricated on the Si/SiO₂ substrates to form an hole injection layer for the C₈-BTBT semiconductor layer. It is found that by exposing MoO₃-coated Au electrodes to ultraviolet/ozone (UV/O₃) the field-effect mobility of top-gate C₈-BTBT FETs significantly increases and the channel-width normalized contact resistance is remarkably reduced to 0.4kΩcm. Top-gate C₈-BTBT FET devices with a channel length of 5μm exhibit high effective mobilities up to 1.4cm²V^-1s^-1. The obtained results indicate that hole doping to C₈-BTBT layers by UV/O₃-treated MoO₃ contributes strongly to the reduction in the access resistance of top-gate C₈-BTBT FETs.