Buffer and Anode Combined Ta Doped In2O2 Electrodes Prepared by Co-sputtering for PEDOT:PSS-free Organic Solar Cells

  • Lee, Hye-Min (Department of Advanced Materials Engineering for Information and Electronics, Kyung Hee University) ;
  • Noh, Yong-Jin (Professional Graduate School of Flexible and Printable Electronics, Polymer Materials Fusion Research Center, Chonbuk National University) ;
  • Na, Seok-In (Professional Graduate School of Flexible and Printable Electronics, Polymer Materials Fusion Research Center, Chonbuk National University) ;
  • Park, Hyun-Woo (Department of Physics, Dankook University) ;
  • Chung, Kwun-Bum (Department of Physics, Dankook University) ;
  • Kima, Han-Ki (Department of Advanced Materials Engineering for Information and Electronics, Kyung Hee University)
  • Published : 2014.02.10

Abstract

We developed poly (3,4-ethylene dioxylene thiophene):poly (styrene sulfonic acid) (PEDOT:PSS)-free organic solar cells (OSCs) using buffer and anode combined Ta doped $In_2O_3$ (ITaO) electrodes. To optimize the ITaO electrodes, we investigated the effect of $Ta_2O_5$ doping power on the electrical, optical, and structural properties of the co-sputtered ITaO films. The optimized ITaO film doped with 20 W $Ta_2O_5$ radio frequency power showed sheet resistance of 17.11 Ohm/square, a transmittance of 93.45%, and a work function of 4.9 eV, all of which are comparable to the value of conventional ITO electrodes. The conventional bulk heterojunction OSC with ITaO anode showed a power conversion efficiency (PCE) of 3.348% similar to the OSCs (3.541%) with an ITO anode. In addition, OSCs fabricated on an ITaO electrode successfully operated without an acidic PEDOT:PSS buffer layer and showed a PCE of 2.634%, which was much higher than the comparable no buffer OSC with an ITO anode. Therefore, co-sputtered ITaO electrodes simultaneously acting as a buffer and an anode layer can be considered promising transparent electrodes for cost-efficient and reliable OSCs because they can eliminate the use of an acidic PEDOT:PSS buffer layer.

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