Origin of reduced polaron recombination in organic semiconductor devices

Deibel, Carsten; Wagenpfahl, Alexander; Dyakonov, Vladimir

doi:10.1103/physrevb.80.075203

Cited by 150 publications

(182 citation statements)

References 32 publications

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“…[37][38][39] Recombination via trap states has been considered as a limiting factor for organic heterojunction solar cells. These traps can originate from shallow tails states 35,[40][41][42] as well as deep trap states at the donor acceptor interface.…”

Section: B Numerical Methodsmentioning

confidence: 99%

Influence of the indium tin oxide/organic interface on open-circuit voltage, recombination, and cell degradation in organic small-molecule solar cells

et al. 2011

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In this paper we investigate the performance and stability of small-molecule organic solar cells with respect to the indium tin oxide (ITO)/organic interface. Different zinc-phthalocyanine (ZnPc)/fullerene (C 60 ) cell architectures with and without ITO O 2 -plasma treatment are compared and tested with respect to their degradation behavior under illumination in inert atmosphere. Photoelectron spectroscopy (UPS and XPS) shows that the O 2 -plasma treatment increases the ITO work function from 4.3 eV up to 5.6 eV. We find that both the increased ITO work function as well as the introduction of an electron blocking layer between ITO and the mixed donor/acceptor layer increases the open-circuit voltage V oc by more than 200 mV. For both cases our continuum approach device simulation quantitatively relates the increase of V oc to a reduced contact recombination and thus a reduced dark current. For cells built on ozone treated ITO we find a fast cell degradation caused by the UV part of the AM 1.5 spectrum. We identify the degradation, which manifests itself in a decrease of V oc of up to 25%, as a partial reversion of the plasma induced ITO work function increase. Additionally, we demonstrate that the degradation can be reduced by structural changes in the cell architecture, leading to improved cell stability. We present a comprehensive study of the recombination at the ITO/organic interface and its influence on the open-circuit voltage and the cell stability.

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Section: B Numerical Methodsmentioning

confidence: 99%

Influence of the indium tin oxide/organic interface on open-circuit voltage, recombination, and cell degradation in organic small-molecule solar cells

et al. 2011

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“…We do this by performing numerical simulations, also taking a physically reasonable reduced and capped bimolecular Langevin-like recombination into account 5 .…”

Section: Introductionmentioning

confidence: 99%

Organic Solar Cell Efficiencies Under the Aspect of Reduced Surface Recombination Velocities

Wagenpfahl

Deibel

Dyakonov

2010

IEEE J. Select. Topics Quantum Electron.

102

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The charge carrier mobility is a key parameter for the organic bulk heterojunction solar cell efficiency. It was recently shown that the interplay charge carrier transport and recombination, both depending on electron and hole mobilities, leads to a point of maximum power conversion efficiency at a finite mobility. Changes of bulk and surface recombination rate, however, can strongly influence this behavior. These processes were previously not considered adequately, as surface recombination velocities of infinity were implicitly assumed or bulk recombination parameters not discussed in detail. In this manuscript, using a macroscopic effective medium simulation, we consider how a reduced bulk recombination process in combination with finite surface recombination velocities affect the power conversion efficiency. Instead of a maximum efficiency at a specific charge carrier mobility, we show that with realistic assumptions and passivated surfaces the efficiency is increased further, saturating only at higher mobilities. Thus, a mobility optimisation is more important for the solar cell performance then previously shown.

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“…Carrier density gradient across the cell has also been proposed to be responsible for the effect. 32,33 In conclusion, we have presented a unified description for the nongeminate recombination in the energy disordered blends that produces naturally both the diffusion-and reaction-limited regime. Our formulation predicts a crossover between these two regimes by change in the carrier density, as a consequence of the increasing role of shallow localized states in the recombination process.…”

mentioning

confidence: 90%

Consistent formulation of the crossover from density to velocity dependent recombination in organic solar cells

Ansari-Rad

García-Belmonte

Bisquert

2015

Applied Physics Letters

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Carrier recombination is a central process in bulk heterojunction organic solar cells. Based on the competition of hopping rates that either implies escape in a broad density of states or recombination across the interface, we formulate a general theory of recombination flux that distinguishes reaction or transport limited recombination according to charge density. The Langevin picture is valid only in the low charge density limit, and a crossover to the reaction controlled regime occurs at higher densities. We present results from impedance spectroscopy of poly(3-hexylthiophene):methanofullerene solar cell that exhibit this crossover.

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Origin of reduced polaron recombination in organic semiconductor devices

Cited by 150 publications

References 32 publications

Influence of the indium tin oxide/organic interface on open-circuit voltage, recombination, and cell degradation in organic small-molecule solar cells

Influence of the indium tin oxide/organic interface on open-circuit voltage, recombination, and cell degradation in organic small-molecule solar cells

Organic Solar Cell Efficiencies Under the Aspect of Reduced Surface Recombination Velocities

Consistent formulation of the crossover from density to velocity dependent recombination in organic solar cells

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