S-shaped current-voltage characteristics of organic solar devices

摘要

Measuring the current-voltage characteristic of organic bulk heterojunctionsolar devices sometimes reveals an s-shaped deformation. We qualitativelyproduce this behaviour by a numerical device simulation assuming a reducedsurface recombination. Furthermore we show how to experimentally create thesedouble diodes by applying an oxygen plasma etch on the indium tin oxide (ITO)anode. Restricted charge transport over material interfaces accumulates spacecharges and therefore creates s-shaped deformations. Finally we discuss theconsequences of our findings for the open circuit voltage $V_{oc}$