Oxygen Contribution for Uniform Formation of Crystalline Zinc Oxide/Polyethylenimine Interfaces to Boost Charge Generation/Transport in Inverted Organic Solar Cells

Abstract

This work demonstrates inverted organic photovoltaics with zinc oxide under an oxygen environment. ZnO films are based on a zinc acetate dihydrate and prepared via annealing in air or argon which performance shows a clear dependence on ZnO formation. We investigated chemical component and crystal structure of ZnO through XPS and XRD. The oxygen contributed ZnO enhances the self-assembly between amine of polyethylenimine (PEI) and hydroxyls, which induces smoothness of ZnO/PEI interface. As a result, PCE with optimized ZnO/PEI exhibited 8.83%, compared to in argon (4.67%). Moreover, oxygen-contributed ZnO/PEI cells lead to air stability with 80% sustained efficiency during the 500 hours. (C) 2017 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.