We report the implementation of continuous, highly flexible, and transparent graphene films obtained by chemical vapor deposition (CVD) as transparent conductive electrodes (TCE) in organic photovoltaic cells. Graphene films were synthesized by CVD, transferred to transparent substrates, and evaluated in organic solar cell heterojunctions. Key to our success is the continuous nature of the CVD graphene films, which led to minimal surface roughness (~0.9 nm) and offered sheet resistance down to 230O/sq (at 72% transparency), much lower than stacked graphene flakes at similar transparency. In addition, solar cells with CVD graphene and indium tin oxide (ITO) electrodes were fabricated side-by-side on flexible polyethylene terephthalate (PET) substrates and were confirmed to offer comparable performance, with power conversion efficiencies (?) of 1.18 and 1.27%, respectively. Furthermore, CVD graphene solar cells demonstrated outstanding capability to operate under bending conditions up to 138�, whereas the ITO-based devices displayed cracks and irreversible failure under bending of 60�. Our work shows that CVD graphene meets the most important criteria of abundance, low cost, conductivity, stability, electrode/organic film compatibility, and flexibility that are necessary to replace ITO in organic photovoltaics, which may have important implications for future organic optoelectronic device.

Graphene synthesis and applications as transparent conductors for organic solar cells

244th National Meeting (2012)

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