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Title: A charge carrier transport model for donor-acceptor blend layers

Highly efficient organic solar cells typically comprise donor-acceptor blend layers facilitating effective splitting of excitons. However, the charge carrier mobility in the blends can be substantially smaller than in neat materials, hampering the device performance. Currently, available mobility models do not describe the transport in blend layers entirely. Here, we investigate hole transport in a model blend system consisting of the small molecule donor zinc phthalocyanine (ZnPc) and the acceptor fullerene C{sub 60} in different mixing ratios. The blend layer is sandwiched between p-doped organic injection layers, which prevent minority charge carrier injection and enable exploiting diffusion currents for the characterization of exponential tail states from a thickness variation of the blend layer using numerical drift-diffusion simulations. Trap-assisted recombination must be considered to correctly model the conductivity behavior of the devices, which are influenced by local electron currents in the active layer, even though the active layer is sandwiched in between p-doped contacts. We find that the density of deep tail states is largest in the devices with 1:1 mixing ratio (E{sub t} = 0.14 eV, N{sub t} = 1.2 × 10{sup 18 }cm{sup −3}) directing towards lattice disorder as the transport limiting process. A combined field and charge carrier density dependent mobility model are developed for thismore » blend layer.« less
Authors:
; ; ; ;  [1] ;  [2] ;  [1] ;  [3] ;  [1] ;  [4]
  1. Institut für Angewandte Photophysik, Technische Universität Dresden, 01062 Dresden (Germany)
  2. Novaled GmbH, Dresden (Germany)
  3. (Switzerland)
  4. (United Kingdom)
Publication Date:
OSTI Identifier:
22413017
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 4; Other Information: (c) 2015 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; COMPUTERIZED SIMULATION; DIFFUSION; DOPED MATERIALS; ELECTRONS; EXCITONS; FULLERENES; HOLES; LAYERS; MIXING RATIO; MOLECULES; ORGANIC SOLAR CELLS; PHTHALOCYANINES; RECOMBINATION; TRANSPORT THEORY; ZINC COMPOUNDS