Performance Improvements in Conjugated Polymer Devices by Removal of Water Induced Traps

Abstract

The exploration of a wide range of molecular structures has led to the development of high-performance conjugated polymer semiconductors for flexible electronic applications including displays, sensor and logic circuits. Nevertheless, many conjugated polymer field-effect transistors (OFETs) exhibit non-ideal device characteristics and device instabilities rendering them unfit for industrial applications. These often do not originate in the material’s intrinsic molecular structure, but rather in external trap states caused by chemical impurities or environmental species such as water. Here we demonstrate a highly efficient mechanism for the removal of water induced traps that are omnipresent in conjugated polymer devices even when processed in inert environments; we show the underlying mechanism by which small molecular additives with water binding nitrile groups or alternatively water-solvent azeotropes are capable of removing water-induced traps leading to a significant improvement in OFETs performance. We also show how certain polymer structures containing strong hydrogen accepting groups will suffer from poor performances due to their high susceptibility to interact with water molecules; this allows us to set forth design guidelines for a next generation of stable, high performing conjugated polymers.