ABSTRACTLayer-by-layer (LbL) assembly is used to create thin films by alternately exposing a substrate to positively- and negatively-charged molecules or particles in water. In recent years, LbL assemblies containing poly(3,4-ethylenedioxythiophene) (PEDOT) have been heavily studied, but little work has focused on improving the environmental stability of these thin films. Most intrinsically conductive polymers suffer from increasing resistance with exposure to ultraviolet light. In the present work, photolytic stability is improved by adding UV-absorbing nanoparticles to PEDOT assemblies. Films made by alternately depositing PEDOT-PSS and polyethylenimine (PEI) show an order of magnitude increase in sheet resistance after just 28 hours of exposure to 365 nm light. This degradation is cut in half by incorporating UV-absorbing nanoparticles, carbon black or titanium dioxide, into these assemblies. After more than 200 hours of exposure, films containing TiO2 nanoparticles have sheet resistance that is one fifth that of the unprotected PEDOT. In addition to adding UV-absorbing particles, the influence of doping and type of polycation on bulk resistivity and film growth were evaluated. These films are able to achieve bulk resistivity values below 1 Ohm cm with a thickness below 100 nm. When combined with transparency greater than 90%, these films may be useful for electrostatic dissipation layers or low conductivity electrodes in film or flexible display applications.
