Comparison of inorganic electron transport layers in fully roll-to-roll coated/printed organic photovoltaics in normal geometry

Abstract

We investigate the suitability of four different inorganic materials (chromium oxide (CrO_X), titanium oxide (TiO_X), aluminium doped zinc oxide (AZO) and zinc oxide (ZnO)) as electrode transport layers in fully roll-to-roll (R2R) fabricated P3HT:ICxA organic solar cells. CrO_X and TiO_X were found to be unsuitable, as the CrO_X devices did not exhibit rectifying behaviour while the TiO_X devices did not withstand the annealing conditions. Of the last two ETLs, ZnO showed by far the most promise with devices demonstrating an average efficiency of 2.2%, which is the highest reported value for R2R devices in normal geometry, and a significantly extended lifetime compared with AZO devices under ISOS-L-2 conditions.