High performance encapsulation of transparent conductive polymers by spatial atomic layer deposition

Abstract

Poly(3,4-ethylenedioxythiophene) (PEDOT) is a transparent conductive polymer widely used in flexible photonic and optoelectronic devices because of its excellent electrical and optical properties. However, its current range of applications is limited by its poor stability under high humidity and solar radiations. Encapsulation is an attractive solution to this problem and the development of a low-temperature and scalable deposition method is highly desirable. In this study, we report the use of spatial atomic layer deposition (SALD) to deposit ultrathin layers of ZnO, TiO2, and Al2O3. These nanolayers maintain the electrical performance of the conductive polymer and its high optical transmittance. The use of SALD ensures low-cost and flexible processing with pinhole-free high-quality coatings at atmospheric pressure and high-throughput. The present study is the first to investigate the effect of various multilayer metal oxide encapsulations on the long-term stability of PEDOT-based transparent conductive materials under solar radiations. We demonstrate finally that bilayer TiO2/Al2O3 and TiO2/ZnO coatings preserve the optoelectronic properties of three different PEDOT-based films, namely PEDOT:OTf (OTf = triflate), PEDOT:Sulf (Sulf = sulfate)and PEDOT:PSS (PSS = PolyStyreneSulfonate) films.