The degradation of indium tin oxide/pentacene/fullerene/tris-8-hydroxy-quinolinato aluminum/aluminum heterojunction organic solar cells: By oxygen or moisture?

The degradation of organic photovoltaic cells (OPVs) based on pentacene/fullerene heterojunction was investigated in air with different relative humidity (RH). The lifetime of OPVs stored in air with 33 +/- 5% RH was about 850 h, 35 times of those stored in air with 65 +/- 5% RH (25 h). Two degradation processes were clearly observed for the devices in low humidity. The results demonstrate that the water and oxygen have different effects on pentacene/fullerene heterojunction OPVs degradation, thus dominating at different time periods. The different decay constants caused by O-2 and H2O might come from the diffusion of O-2 and H2O, respectively. Water is believed to be more important in the degradation process of pentacene/C-60 based solar cells. (C) 2010 Elsevier B.V. All rights reserved.