Moderately reduced graphene oxide via UV-ozone treatment as hole transport layer for high efficiency organic solar cells

Abstract

Abstract This work demonstrates a new hole transport layer (HTL) via UV-ozone assisted moderate reduction of graphene oxide (GO) in organic solar cells (OSCs). The XPS and Raman measurements confirmed the successful reduction/removal of oxygen functional groups after UV-ozone treatment. Remarkably enhanced performance of the OSCs was demonstrated by the 15 min treated device with power conversion efficiency (PCE) of 4.07%, followed by the 10 min device with almost similar PCE of 4.03%, as compared to the device with untreated GO HTL exhibiting a much lower PCE of 2.80%. The significant enhancement in the device performance is attributed to the moderate reduction of oxygen functional groups, leaving behind highly conductive graphene as well as the decreased series resistance, increased shunt resistance and comparatively smooth HTL morphology. Further, it is also ascribed to enhanced short circuit current density, open circuit voltage and fill factor of UV-ozone treated GO which directly contributed to the improved PCE. Moreover, the OSCs with the UV-ozone treated GO HTL showed very good stability over the 250 h of exposure to ambient atmosphere.