Flexible Graphene Electrode-Based Organic Photovoltaics with Record-High Efficiency

Flexible organic and hybrid organic-inorganic solar cells require both the flexible photoactive media and flexible electrodes with good conductivity and transparency. Graphene has been proposed as a promising flexible electrode due to its mechanical and chemical robustness, excellent electrical and optical properties, and potentially low-cost processing.  We have designed graphene electrode-based flexible polymer solar cells with thieno[3,4-b]thiophene/benzodithiophene (PTB7) and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) by resolving the issues occurring at the interface between graphene and charge transporting semiconducting materials.  We demonstrate highly efficient flexible devices with power conversion efficiencies of 6.1% (anode) and 7.1% (cathode) achieved via thermal treatment of molybdenum trioxide (MoO₃) electron blocking layer, direct deposition of ZnO electron transporting layer on graphene. The advances in this work demonstrate graphene has great potential as a promising transparent electrode in a variety of flexible optoelectronic devices.