Influence of equilibrium charge reservoir formation on photo generated charge transport in TiO2/organic devices

Simon Sandén, Oskar Sandberg, Q. Xu, Jan-Henrik Smått, G. Juska, M. Lindén, Ronald Österbacka

    Research output: Contribution to journalArticleScientificpeer-review

    10 Citations (Scopus)

    Abstract

    Charge transport measurements have been performed using the photo induced charge extraction by linearly increasing voltage (photo-CELIV) technique on indium tin oxide/titanium dioxide/ poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester/copper (ITO/TiO2/P3HT:PCBM/Cu) devices. By adjusting the offset voltage such that holes are accumulated at the ITO/TiO2 contact we obtain space charge limited current (SCLC) extraction in the dark. Using photo-generation the current response is limited by SCLC extraction at low carrier concentrations but becomes purely recombination limited at high photo-generated carrier concentration. A 1-D drift diffusion model has been developed to simulate our results and we show that the hole blocking ITO/TiO2 contact is responsible for the SCLC behavior. The highly reduced recombination of charges seen in P3HT: PCBM devices is necessary to obtain the large extraction current transients that are seen in the experimental measurements. By comparing the simulated dark CELIV and photo-CELIV we show that photo-generated extraction is more sensitive towards changes in the surface recombination velocity. (C) 2014 Elsevier B.V. All rights reserved.
    Original languageUndefined/Unknown
    Pages (from-to)3506–3513
    Number of pages8
    JournalOrganic Electronics
    Volume15
    Issue number12
    DOIs
    Publication statusPublished - 2014
    MoE publication typeA1 Journal article-refereed

    Keywords

    • Blocking layer
    • Bulk-hetero junction
    • Charge transport
    • Photo-CELIV
    • TiO2

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