Graphene as transparent conducting electrodes in organic photovoltaics: studies in graphene morphology, hole transporting layers, and counter electrodes.

In this work, organic photovoltaics (OPV) with graphene electrodes are constructed where the effect of graphene morphology, hole transporting layers (HTL), and counter electrodes are presented. Instead of the conventional poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) PEDOT:PSS HTL, an alternative transition metal oxide HTL (molybdenum oxide (MoO(3))) is investigated to address the issue of surface immiscibility between graphene and PEDOT:PSS. Graphene films considered here are synthesized via low-pressure chemical vapor deposition (LPCVD) using a copper catalyst and experimental issues concerning the transfer of synthesized graphene onto the substrates of OPV are discussed. The morphology of the graphene electrode and HTL wettability on the graphene surface are shown to play important roles in the successful integration of graphene films into the OPV devices. The effect of various cathodes on the device performance is also studied. These factors (i.e., suitable HTL, graphene surface morphology and residues, and the choice of well-matching counter electrodes) will provide better understanding in utilizing graphene films as transparent conducting electrodes in future solar cell applications.

[1]  K. Loh,et al.  Interface Engineering of Layer‐by‐Layer Stacked Graphene Anodes for High‐Performance Organic Solar Cells , 2011, Advanced materials.

[2]  V. Bulović,et al.  Doped graphene electrodes for organic solar cells , 2010, Nanotechnology.

[3]  Jong-Hyun Ahn,et al.  High-performance flexible graphene field effect transistors with ion gel gate dielectrics. , 2010, Nano letters.

[4]  Kwang S. Kim,et al.  Roll-to-roll production of 30-inch graphene films for transparent electrodes. , 2010, Nature nanotechnology.

[5]  Robert C. Tenent,et al.  Carbon nanotube network electrodes enabling efficient organic solar cells without a hole transport layer , 2010 .

[6]  Do-Young Kim,et al.  Energy level evolution of air and oxygen exposed molybdenum trioxide films , 2010 .

[7]  Chongwu Zhou,et al.  Continuous, highly flexible, and transparent graphene films by chemical vapor deposition for organic photovoltaics. , 2010, ACS nano.

[8]  J. Bernède,et al.  Effects of the buffer layer inserted between the transparent conductive oxide anode and the organic electron donor , 2010 .

[9]  C. Dimitrakopoulos,et al.  100-GHz Transistors from Wafer-Scale Epitaxial Graphene , 2010, Science.

[10]  Wolfgang Kowalsky,et al.  Role of the deep-lying electronic states of MoO3 in the enhancement of hole-injection in organic thin films , 2009 .

[11]  Byung Doo Chin,et al.  Influence of metal cathode for organic photovoltaic device performance , 2009 .

[12]  Yu Wang,et al.  Large area, continuous, few-layered graphene as anodes in organic photovoltaic devices , 2009 .

[13]  A. Reina,et al.  Large area, few-layer graphene films on arbitrary substrates by chemical vapor deposition. , 2009, Nano letters.

[14]  S. Banerjee,et al.  Large-Area Synthesis of High-Quality and Uniform Graphene Films on Copper Foils , 2009, Science.

[15]  Valeria Russo,et al.  Logic gates with a single graphene transistor , 2009 .

[16]  B. H. Weiller,et al.  Practical chemical sensors from chemically derived graphene. , 2009, ACS nano.

[17]  K. Jenkins,et al.  Operation of graphene transistors at gigahertz frequencies. , 2008, Nano letters.

[18]  Priscilla Kailian Ang,et al.  Solution-gated epitaxial graphene as pH sensor. , 2008, Journal of the American Chemical Society.

[19]  Zhenan Bao,et al.  Organic solar cells with solution-processed graphene transparent electrodes , 2008 .

[20]  G. Eda,et al.  Large-area ultrathin films of reduced graphene oxide as a transparent and flexible electronic material. , 2008, Nature nanotechnology.

[21]  J. Flege,et al.  Epitaxial graphene on ruthenium. , 2008, Nature materials.

[22]  G. Fudenberg,et al.  Ultrahigh electron mobility in suspended graphene , 2008, 0802.2389.

[23]  A. Bachtold,et al.  Current-induced cleaning of graphene , 2007, 0709.0607.

[24]  S. Stankovich,et al.  Synthesis of graphene-based nanosheets via chemical reduction of exfoliated graphite oxide , 2007 .

[25]  E. Williams,et al.  Atomic structure of graphene on SiO2. , 2007, Nano letters.

[26]  Scott S. Verbridge,et al.  Electromechanical Resonators from Graphene Sheets , 2007, Science.

[27]  K. Novoselov,et al.  Detection of individual gas molecules adsorbed on graphene. , 2006, Nature materials.

[28]  Liangbing Hu,et al.  Organic solar cells with carbon nanotube network electrodes , 2006 .

[29]  C. Berger,et al.  Electronic Confinement and Coherence in Patterned Epitaxial Graphene , 2006, Science.

[30]  Vishal Shrotriya,et al.  Transition metal oxides as the buffer layer for polymer photovoltaic cells , 2006 .

[31]  Husnu Emrah Unalan,et al.  Conducting and transparent single-wall carbon nanotube electrodes for polymer-fullerene solar cells , 2005 .

[32]  K. Novoselov,et al.  Two-dimensional atomic crystals. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[33]  Valentin D. Mihailetchi,et al.  Effect of metal electrodes on the performance of polymer : fullerene bulk heterojunction solar cells , 2004 .

[34]  Niyazi Serdar Sariciftci,et al.  Organic solar cells: An overview , 2004 .

[35]  V. Mihailetchi,et al.  Cathode dependence of the open-circuit voltage of polymer:fullerene bulk heterojunction solar cells , 2003 .

[36]  Stephen R. Forrest,et al.  Small molecular weight organic thin-film photodetectors and solar cells , 2003 .

[37]  Richard H. Friend,et al.  Inorganic solution-processed hole-injecting and electron-blocking layers in polymer light-emitting diodes , 2002 .

[38]  Klaus Meerholz,et al.  Influence of the anodic work function on the performance of organic solar cells. , 2002, Chemphyschem : a European journal of chemical physics and physical chemistry.

[39]  J. Nelson.  Organic photovoltaic films , 2002 .

[40]  C. Brabec,et al.  Origin of the Open Circuit Voltage of Plastic Solar Cells , 2001 .

[41]  C. Tang.  Two‐layer organic photovoltaic cell , 1986 .

[42]  H. Michaelson.  The work function of the elements and its periodicity , 1977 .