Application of sputter-deposited amorphous and anatase TiO2 as electron-collecting layers in inverted organic photovoltaics

We demonstrate the deposition of amorphous and anatase TiO2 on indium tin oxide (ITO) substrates via the process of sputtering, and the use of these materials as electron-collecting layers (ECLs) in inverted-type organic photovoltaics (OPVs). Anatase TiO2 was obtained via vacuum-annealing of as-deposited amorphous TiO2 at 300 degrees C. No deterioration of optical and electrical properties of ITO was observed after both sputter-deposition of TiO2 and annealing process. The anatase TiO2 proved to be an effective ECL when employed in inverted OPVs using bulk heterojunction photoactive layer of poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester, achieving a power conversion efficiency of 3.3% (J(SC) = 9.0 mA cm(-2), V-OC = 0.62 V and FF = 0.60). (C) 2013 Elsevier B.V. All rights reserved.