Generic roll-to-roll compatible method for insolubilizing and stabilizing conjugated active layers based on low energy electron irradiation

Abstract

Irradiation of organic multilayer films is demonstrated as a powerful method to improve several properties of polymer thin films and devices derived from them. The chemical cross-linking that is the direct result of the irradiation with 100 keV electrons is fast and has a penetration power compatible with thin plastic foils of one to two hundreds of microns typical of devices explored in organic electronics. We demonstrate here that active layers and complete devices can be subjected to electron irradiation-induced cross-linking thus facilitating multilayer solvent processing and morphological stability. The method is fast, generic, contactless, and fully compatible with high-speed roll-to-roll processing of i.e. polymer solar cells at web speeds in excess of 60 m min-1. We employ fully printed, flexible, and foil-based indium-tin-oxide free polymer solar cells in this study to demonstrate the technique. We also demonstrate that polymer solar cells are exceptionally stable towards ionizing radiation and find that doses as high as 100 kGy can be used before any significant decrease in performance is observed. Copyright © 2014 Wiley Periodicals, Inc.