Get access

Water-Soluble Polyfluorenes as an Interfacial Layer Leading to Cathode-Independent High Performance of Organic Solar Cells

Authors

  • Seung-Hwan Oh,

    1. Research Institute for Solar and Sustainable Energies (RISE) Gwangju Institute of Science and Technology (GIST) 261 Cheomdan-gwagiro (Oryong-dong), Buk-Gu, Gwangju 500-712 (Korea)
    Search for more papers by this author
  • Seok-In Na,

    1. Institute of Advanced Composite Materials Korea Institute of Science and Technology (KIST)864-9, Dunsan-ri, Bongdong-eup, Wanju-gun, Jeollabuk-do 565-902 (Korea)
    Search for more papers by this author
  • Jang Jo,

    1. Department of Nanobiomaterials and Electronics, Department of Materials Science and Engineering, Heeger Center for Advanced Materials (HCAM) Gwangju Institute of Science and Technology (GIST) 261 Cheomdan-gwagiro (Oryong-dong), Buk-Gu, Gwangju 500-712 (Korea)
    Search for more papers by this author
  • Bogyu Lim,

    1. Department of Nanobiomaterials and Electronics, Department of Materials Science and Engineering, Heeger Center for Advanced Materials (HCAM) Gwangju Institute of Science and Technology (GIST) 261 Cheomdan-gwagiro (Oryong-dong), Buk-Gu, Gwangju 500-712 (Korea)
    Search for more papers by this author
  • Doojin Vak,

    1. Bio21 Institute, University of Melbourne30 Flemington Road, Parkville, Victoria 3010 (Australia)
    Search for more papers by this author
  • Dong-Yu Kim

    Corresponding author
    1. Department of Nanobiomaterials and Electronics, Department of Materials Science and Engineering, Heeger Center for Advanced Materials (HCAM) Gwangju Institute of Science and Technology (GIST) 261 Cheomdan-gwagiro (Oryong-dong), Buk-Gu, Gwangju 500-712 (Korea)
    • Department of Nanobiomaterials and Electronics, Department of Materials Science and Engineering, Heeger Center for Advanced Materials (HCAM) Gwangju Institute of Science and Technology (GIST) 261 Cheomdan-gwagiro (Oryong-dong), Buk-Gu, Gwangju 500-712 (Korea)
    Search for more papers by this author

Abstract

Novel poly[(9,9-bis((6′-(N,N,N-trimethylammonium)hexyl)-2,7-fluorene)-alt-(9,9-bis(2-(2-(2-methoxyethoxy)ethoxy)ethyl)-9-fluorene)) dibromide (WPF-6-oxy-F) and poly[(9,9-bis((6′-(N,N,N-trimethylammonium)hexyl)-2,7-fluorene)-alt-(9,9-bis(2-(2-methoxyethoxy)ethyl)-fluorene)] dibromide (WPF-oxy-F) compounds are developed and the use of these water-soluble polymers as an interfacial layer for low-cost poly(3-hexylthiophene):phenyl-C61 butyric acid methyl ester (P3HT:PCBM) organic solar cells (OSCs) is investigated. When WPF-oxy-F or WPF-6-oxy-F is simply inserted between the active layer and the cathode as an interfacial dipole layer by spin-coating water-soluble polyfluorenes, the open-circuit voltage (Voc), fill factor (FF), and power-conversion efficiency (PCE) of photovoltaic cells with high work-function metal cathodes, such as Al, Ag, Au, and Cu, dramatically increases. For example, when WPF-6-oxy-F is used with Al, Ag, Au, or Cu, regardless of the work-function of the metal cathode, the Voc is 0.64, 0.64, 0.58, and 0.63 V, respectively, approaching the original value of the P3HT:PCBM system because of the formation of large interfacial dipoles through a reduction of the metal work-function. In particular, introducing WPF-6-oxy-F into a low-cost Cu cathode dramatically enhanced the device efficiency from 0.8% to 3.36%.

Ancillary