Air-processed organic photovoltaic devices fabricated with hot press lamination

A detailed method for air-processed, inverted Organic Photovoltaic (OPV) devices using lamination of the metal electrode with a doped conducting polymer adhesive is presented. A poly(3-hexylthiophene) (P3HT) - [6,6] phenyl C-61 butyric methyl ester (PCBM) bulk heterojunction is used, with a solution-processed ZnO electron collection layer. The top contact consists of modified polyethylene dioxythiophene: polystyrene sulfonate (PEDOT:PSS) that is spin-coated onto a Ag electrode, and the entire structure is laminated onto the active layer. Lamination produces devices with 3.19% power conversion efficiency at 1 sun illumination, which is higher than the value for control devices produced with the standard sequential process with an evaporated top metal electrode. The laminated interface yields an ohmic contact, as shown by the high fill factor and low series resistance of the laminated devices compared to devices with a thermally evaporated top metal electrode. We examine the lamination parameters and their effect on device performance, and we identify the treatment of the adhesion layer to be one of the more important parameters to control for efficient devices. The optimized protocol described here allows one to fabricate efficient inverted OPV devices in air, without the need for an expensive, high quality evaporation chamber for top contact deposition. (C) 2010 Elsevier B. V. All rights reserved.