Graphene intermediate layer in tandem organic photovoltaic cells

Abstract

One strategy to harvest wide spectral solar energy is to stack different bandgap materials together in a tandem solar cell. Here, it is demonstrated that CVD grown graphene film can be employed as intermediate layer (IML) in tandem solar cells. Using MoO3-modified graphene IML, a high open circuit voltage (Voc) of 1 V and a high short-circuit current density (J sc) of 11.6 mA cm-2 could be obtained in series and parallel connection, respectively, in contrast to a Voc of 0.58 V and Jsc of 7.6 mA cm-2 in single PV cell. The value of V oc (Jsc) in the tandem cell is very close to the sum of Voc (Jsc) attained from two single subcells in series (parallel), which confirms good ohmic contact at the photoactive layer/MoO 3-modified graphene interface. Work function engineering of the graphene IML with metal oxide is essential to ensure good charge collection from both subcells. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.