Low bandgap alternating polyfluorene copolymers in plastic photodiodes and solar cells

We report a comparative study of plastic photodiodes using four different copolymers of fluorene, with a variation of alkyl side chain length and chemical structure. Photodiode materials are formed by blending the polymers with a fullerene derivative and spincoating the blend solution. A photovoltage of 1 V is obtained in devices, where the anode is a doped polymer and the cathode is LiF/Al. Monochromatic quantum efficiencies are better than 40% over most of the absorption range, and under solar light AM 1.5 simulation, we reach energy efficiencies beyond 2%. The high fill factors obtained in some of the devices indicate that these are of interest for more elaborate optimisation. Reasons for the benign electrical transport are discussed.

[1]  M. Grätzel,et al.  A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films , 1991, Nature.

[2]  Christoph J. Brabec,et al.  The influence of materials work function on the open circuit voltage of plastic solar cells , 2002 .

[3]  R. Friend,et al.  Efficient light harvesting in a photovoltaic diode composed of a semiconductor conjugated copolymer blend , 2002 .

[4]  J. Hummelen,et al.  Polymer Photovoltaic Cells: Enhanced Efficiencies via a Network of Internal Donor-Acceptor Heterojunctions , 1995, Science.

[5]  Yang Yang,et al.  Efficient Photoluminescence and Electroluminescence from a Soluble Polyfluorene , 1996 .

[6]  C. Brabec,et al.  Plastic Solar Cells , 2001 .

[7]  D. Bradley,et al.  Efficient polyfluorene based solar cells , 2003 .

[8]  Lenneke H. Slooff,et al.  Photoinduced Electron Transfer and Photovoltaic Response of a MDMO‐PPV:TiO2 Bulk‐Heterojunction , 2003 .

[9]  Josef Salbeck,et al.  Solid-state dye-sensitized mesoporous TiO2 solar cells with high photon-to-electron conversion efficiencies , 1998, Nature.

[10]  Jie Yao,et al.  Preparation and Characterization of Fulleroid and Methanofullerene Derivatives , 1995 .

[11]  Katsumi Yoshino,et al.  Synthesis of fusible and soluble conducting polyfluorene derivatives and their characteristics , 1993 .

[12]  Richard H. Friend,et al.  The origin of the open-circuit voltage in polyfluorene-based photovoltaic devices , 2002 .

[13]  R. Friend,et al.  ESEM imaging of polyfluorene blend cross-sections for organic devices , 2002 .

[14]  Donal D. C. Bradley,et al.  Dispersive electron transport in an electroluminescent polyfluorene copolymer measured by the current integration time-of-flight method , 2001 .

[15]  Richard H. Friend,et al.  Vertically segregated polymer-blend photovoltaic thin-film structures through surface-mediated solution processing , 2002 .

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

[17]  Donal D. C. Bradley,et al.  A glass‐forming conjugated main‐chain liquid crystal polymer for polarized electroluminescence applications , 1997 .

[18]  Richard H. Friend,et al.  Charge Generation Kinetics and Transport Mechanisms in Blended Polyfluorene Photovoltaic Devices , 2002 .

[19]  M. Leclerc.  Polyfluorenes: Twenty years of progress , 2001 .

[20]  Richard H. Friend,et al.  Photodiodes Based on Polyfluorene Composites: Influence of Morphology , 2000 .

[21]  James J. O'Brien,et al.  Progress with Light‐Emitting Polymers , 2000 .

[22]  R. Friend,et al.  Fluorescence scanning near‐field optical microscopy of polyfluorene composites , 2001, Journal of microscopy.

[23]  K. Yoshino,et al.  Novel Photophysical Properties of Fullerene Doped Conducting Polymers , 1994 .

[24]  Richard H. Friend,et al.  Photovoltaic Performance and Morphology of Polyfluorene Blends: A Combined Microscopic and Photovoltaic Investigation , 2001 .

[25]  A. Arias,et al.  Raman microscopy determination of phase composition in polyfluorene composites , 2001 .

[26]  C. A. Walsh,et al.  Efficient photodiodes from interpenetrating polymer networks , 1995, Nature.

[27]  Donal D. C. Bradley,et al.  Mobility enhancement in conjugated polymer field-effect transistors through chain alignment in a liquid-crystalline phase , 2000 .

[28]  A. J. Heeger,et al.  Photoinduced Electron Transfer from a Conducting Polymer to Buckminsterfullerene , 1992, Science.

[29]  Mats Andersson,et al.  High‐Performance Polymer Solar Cells of an Alternating Polyfluorene Copolymer and a Fullerene Derivative , 2003 .