Efficient bulk-heterojunction photovoltaic cells with transparent multi-layer graphene electrodes

We present the results of applying multi-layer graphene (MLG) films as transparent conductive electrodes in organic photovoltaic devices (OPVs). The MLG films synthesized at different growth temperatures by chemical vapor deposition were applied to OPVs. The performance of OPVs with 1000 °C-grown MLG films was found to be the best with a power conversion efficiency (PCE) of ∼1.3%. The PCE was further enhanced when a hole-blocking TiOX layer was inserted in the device structure, resulting in a PCE of ∼2.6% which is a significantly higher efficiency compared to other previously reported graphene-adopted photovoltaic cells. Our demonstration of the PCE-increase in the graphene-electrode OPVs may foster the application of the fast-progressing graphene technology toward more practical OPV technology.