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Title: Structural influences on charge carrier dynamics for small-molecule organic photovoltaics

We investigated the structural influences on the charge carrier dynamics in zinc phthalocyanine/fullerene (ZnPc/C{sub 60}) photovoltaic cells by introducing poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and 2,5-bis(4-biphenylyl)-bithiophene (BP2T) between indium tin oxide and ZnPc layers. ZnPc films can be tuned to be round, long fiber-like, and short fiber-like structure, respectively. Time-resolved microwave conductivity measurements reveal that charge carrier lifetime in ZnPc/C{sub 60} bilayer films is considerably affected by the intra-grain properties. Transient photocurrent of ZnPc single films indicated that the charge carriers can transport for a longer distance in the long fiber-like grains than that in the round grains, due to the greatly lessened grain boundaries. By carefully controlling the structure of ZnPc films, the short-circuit current and fill factor of a ZnPc/C{sub 60} heterojunction solar cell with BP2T are significantly improved and the power conversion efficiency is increased to 2.6%, which is 120% larger than the conventional cell without BP2T.
Authors:
; ; ; ;  [1] ;  [1] ;  [2] ; ;  [3] ;  [4]
  1. Research Center for Photovoltaic Technologies, National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 5, 1-1-1 Higashi, 305-8565 Tsukuba (Japan)
  2. (JST), 4-1-8 Honcho Kawaguchi, 332-0012 Saitama (Japan)
  3. Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, 565-0871 Suita, Osaka (Japan)
  4. Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 5, 1-1-1 Higashi, 305-8565 Tsukuba (Japan)
Publication Date:
OSTI Identifier:
22306243
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 1; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CHARGE CARRIERS; CURRENTS; EFFICIENCY; ELECTRICAL FAULTS; FILL FACTORS; FILMS; FULLERENES; GRAIN BOUNDARIES; HETEROJUNCTIONS; LAYERS; LIFETIME; MOLECULES; PHOTOVOLTAIC EFFECT; PHTHALOCYANINES; SOLAR CELLS; TIME RESOLUTION; TRANSIENTS; ZINC COMPLEXES