The Experts below are selected from a list of 675 Experts worldwide ranked by ideXlab platform

Steve Albrecht - One of the best experts on this subject based on the ideXlab platform.

  • impact of charge transport on current voltage characteristics and power conversion efficiency of organic solar cells
    Nature Communications, 2015
    Co-Authors: Steve Albrecht, Dieter Neher, Uli Wurfel, Annika Spies
    Abstract:

    This work elucidates the impact of charge transport on the photovoltaic properties of organic solar cells. Here we show that the analysis of current–voltage curves of organic solar cells under illumination with the Shockley Equation results in values for ideality factor, photocurrent and parallel resistance, which lack physical meaning. Drift-diffusion simulations for a wide range of charge-carrier mobilities and illumination intensities reveal significant carrier accumulation caused by poor transport properties, which is not included in the Shockley Equation. As a consequence, the separation of the quasi Fermi levels in the organic photoactive layer (internal voltage) differs substantially from the external voltage for almost all conditions. We present a new analytical model, which considers carrier transport explicitly. The model shows excellent agreement with full drift-diffusion simulations over a wide range of mobilities and illumination intensities, making it suitable for realistic efficiency predictions for organic solar cells.

Christian Jooss - One of the best experts on this subject based on the ideXlab platform.

  • current voltage characteristics of manganite titanite perovskite junctions
    Beilstein Journal of Nanotechnology, 2015
    Co-Authors: Benedikt Ifland, Patrick Peretzki, Birte Kressdorf, P Saring, Andreas Kelling, M Seibt, Christian Jooss
    Abstract:

    After a general introduction into the Shockley theory of current voltage (J-V) characteristics of inorganic and organic semiconductor junctions of different bandwidth, we apply the Shockley theory-based, one diode model to a new type of perovskite junctions with polaronic charge carriers. In particular, we studied manganite-titanate p-n heterojunctions made of n-doped SrTi1- y Nb y O3, y = 0.002 and p-doped Pr1- x Ca x MnO3, x = 0.34 having a strongly correlated electron system. The diffusion length of the polaron carriers was analyzed by electron beam-induced current (EBIC) in a thin cross plane lamella of the junction. In the J-V characteristics, the polaronic nature of the charge carriers is exhibited mainly by the temperature dependence of the microscopic parameters, such as the hopping mobility of the series resistance and a colossal electro-resistance (CER) effect in the parallel resistance. We conclude that a modification of the Shockley Equation incorporating voltage-dependent microscopic polaron parameters is required. Specifically, the voltage dependence of the reverse saturation current density is analyzed and interpreted as a voltage-dependent electron-polaron hole-polaron pair generation and separation at the interface.

  • Current–voltage characteristics of manganite–titanite perovskite junctions
    Beilstein-Institut, 2015
    Co-Authors: Benedikt Ifland, Patrick Peretzki, Birte Kressdorf, P Saring, Andreas Kelling, M Seibt, Christian Jooss
    Abstract:

    After a general introduction into the Shockley theory of current voltage (J–V) characteristics of inorganic and organic semiconductor junctions of different bandwidth, we apply the Shockley theory-based, one diode model to a new type of perovskite junctions with polaronic charge carriers. In particular, we studied manganite–titanate p–n heterojunctions made of n-doped SrTi1−yNbyO3, y = 0.002 and p-doped Pr1−xCaxMnO3, x = 0.34 having a strongly correlated electron system. The diffusion length of the polaron carriers was analyzed by electron beam-induced current (EBIC) in a thin cross plane lamella of the junction. In the J–V characteristics, the polaronic nature of the charge carriers is exhibited mainly by the temperature dependence of the microscopic parameters, such as the hopping mobility of the series resistance and a colossal electro-resistance (CER) effect in the parallel resistance. We conclude that a modification of the Shockley Equation incorporating voltage-dependent microscopic polaron parameters is required. Specifically, the voltage dependence of the reverse saturation current density is analyzed and interpreted as a voltage-dependent electron–polaron hole–polaron pair generation and separation at the interface

Uli Wurfel - One of the best experts on this subject based on the ideXlab platform.

  • impact of charge transport on current voltage characteristics and power conversion efficiency of organic solar cells
    Nature Communications, 2015
    Co-Authors: Steve Albrecht, Dieter Neher, Uli Wurfel, Annika Spies
    Abstract:

    This work elucidates the impact of charge transport on the photovoltaic properties of organic solar cells. Here we show that the analysis of current–voltage curves of organic solar cells under illumination with the Shockley Equation results in values for ideality factor, photocurrent and parallel resistance, which lack physical meaning. Drift-diffusion simulations for a wide range of charge-carrier mobilities and illumination intensities reveal significant carrier accumulation caused by poor transport properties, which is not included in the Shockley Equation. As a consequence, the separation of the quasi Fermi levels in the organic photoactive layer (internal voltage) differs substantially from the external voltage for almost all conditions. We present a new analytical model, which considers carrier transport explicitly. The model shows excellent agreement with full drift-diffusion simulations over a wide range of mobilities and illumination intensities, making it suitable for realistic efficiency predictions for organic solar cells.

Keith W. J. Barnham - One of the best experts on this subject based on the ideXlab platform.

  • Charge transport in hybrid nanorod-polymer composite photovoltaic cells
    Physical Review B - Condensed Matter and Materials Physics, 2003
    Co-Authors: Wendy U. Huynh, Janke J. Dittmer, Nerayo Teclemariam, Armand P Alivisatos, Delia J. Milliron, Keith W. J. Barnham
    Abstract:

    Charge transport in composites of inorganic nanorods and a conjugated polymer is investigated using a photovoltaic device structure. We show that the current-voltage (I-V) curves in the dark can be modeled using the Shockley Equation modified to include series and shunt resistance at low current levels, and using an improved model that incorporates both the Shockley Equation and the presence of a space-charge limited region at high currents. Under illumination the efficiency of photocurrent generation is found to be dependent on applied bias. Furthermore, the photocurrent-light intensity dependence was found to be sublinear. An analysis of the shunt resistance as a function of light intensity suggests that the photocurrent as well as the fill factor is diminished as a result of increased photoconductivity of the active layer at high light intensity. By studying the intensity dependence of the open circuit voltage for nanocrystals with different diameters and thus band gaps, it was inferred that Fermi-level pinning occurs at the interface between the aluminum electrode and the nanocrystal.

Dieter Neher - One of the best experts on this subject based on the ideXlab platform.

  • a new figure of merit for organic solar cells with transport limited photocurrents
    Scientific Reports, 2016
    Co-Authors: Dieter Neher, Juliane Kniepert, Arik Elimelech, Jan Anton L Koster
    Abstract:

    Compared to their inorganic counterparts, organic semiconductors suffer from relatively low charge carrier mobilities. Therefore, expressions derived for inorganic solar cells to correlate characteristic performance parameters to material properties are prone to fail when applied to organic devices. This is especially true for the classical Shockley-Equation commonly used to describe current-voltage (JV)-curves, as it assumes a high electrical conductivity of the charge transporting material. Here, an analytical expression for the JV-curves of organic solar cells is derived based on a previously published analytical model. This expression, bearing a similar functional dependence as the Shockley-Equation, delivers a new figure of merit α to express the balance between free charge recombination and extraction in low mobility photoactive materials. This figure of merit is shown to determine critical device parameters such as the apparent series resistance and the fill factor.

  • impact of charge transport on current voltage characteristics and power conversion efficiency of organic solar cells
    Nature Communications, 2015
    Co-Authors: Steve Albrecht, Dieter Neher, Uli Wurfel, Annika Spies
    Abstract:

    This work elucidates the impact of charge transport on the photovoltaic properties of organic solar cells. Here we show that the analysis of current–voltage curves of organic solar cells under illumination with the Shockley Equation results in values for ideality factor, photocurrent and parallel resistance, which lack physical meaning. Drift-diffusion simulations for a wide range of charge-carrier mobilities and illumination intensities reveal significant carrier accumulation caused by poor transport properties, which is not included in the Shockley Equation. As a consequence, the separation of the quasi Fermi levels in the organic photoactive layer (internal voltage) differs substantially from the external voltage for almost all conditions. We present a new analytical model, which considers carrier transport explicitly. The model shows excellent agreement with full drift-diffusion simulations over a wide range of mobilities and illumination intensities, making it suitable for realistic efficiency predictions for organic solar cells.