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Laurence M. Peter - One of the best experts on this subject based on the ideXlab platform.

  • Determination of the Electron Diffusion Length in Dye-Sensitized Solar Cells by Substrate Contact Patterning
    Journal of Physical Chemistry C, 2011
    Co-Authors: Halina K. Dunn, Per-oskar Westin, Daniel R. Staff, Alison B. Walker, Gerrit Boschloo, Laurence M. Peter, Anders Hagfeldt
    Abstract:

    A new method to estimate the Electron Diffusion Length in dye-sensitized solar cells (DSCs) is presented. DSCs were fabricated on conducting glass substrates that were patterned by laser ablation of the fluorine-doped tin oxide coating to form parallel contact strips separated by uncontacted strips of the same width. The relative collection efficiency was measured as a function of the gap between the contact strips, which determines the lateral distance traveled by Electrons to reach the contacts. To avoid complications arising from nonlinear recombination kinetics, current measurements were performed using small amplitude perturbations of the Electron density close to open circuit and the maximum power point to minimize Electron density gradients in the film. One and two-dimensional solutions of the continuity equation for Electron transport and back reaction predict that the relative collection efficiency should fall as spacing between the contact strips exceeds the Electron Diffusion Length and Electrons are lost by back Electron transfer during transit to the contacts. Measurements of the relative collection efficiency were fitted to the predicted dependence of the collection efficiency on the spacing between the contact strips to obtain the value of the Electron Diffusion Length. The Diffusion Length is found to increase with voltage both at open circuit and at the maximum power point.

  • Electron Diffusion and back reaction in dye sensitized solar cells the effect of nonlinear recombination kinetics
    Journal of Physical Chemistry Letters, 2010
    Co-Authors: Julio Villanuevacab, Gerko Oskam, Hongxia Wang, Laurence M. Peter
    Abstract:

    The Electron collection efficiency in dye-sensitized solar cells (DSCs) is usually related to the Electron Diffusion Length, L = (Dτ)1/2, where D is the Diffusion coefficient of mobile Electrons and τ is their lifetime, which is determined by Electron transfer to the redox electrolyte. Analysis of incident photon-to-current efficiency (IPCE) spectra for front and rear illumination consistently gives smaller values of L than those derived from small amplitude methods. We show that the IPCE analysis is incorrect if recombination is not first-order in free Electron concentration, and we demonstrate that the intensity dependence of the apparent L derived by first-order analysis of IPCE measurements and the voltage dependence of L derived from perturbation experiments can be fitted using the same reaction order, γ ≈ 0.8. The new analysis presented in this letter resolves the controversy over why L values derived from small amplitude methods are larger than those obtained from IPCE data.

  • a comparison of different methods to determine the Electron Diffusion Length in dye sensitized solar cells
    Journal of Physical Chemistry C, 2009
    Co-Authors: Hongxia Wang, Laurence M. Peter
    Abstract:

    A new steady-state method for determination of the Electron Diffusion Length in dye-sensitized solar cells (DSCs) is described and illustrated with data obtained using cells containing three different types of electrolyte. The method is based on using near-IR absorbance methods to establish pairs of illumination intensity for which the total number of trapped Electrons is the same at open circuit (where all Electrons are lost by interfacial Electron transfer) as at short circuit (where the majority of Electrons are collected at the contact). Electron Diffusion Length values obtained by this method are compared with values derived by intensity-modulated methods and by impedance measurements under illumination. The results indicate that the values of Electron Diffusion Length derived from the steady-state measurements are consistently lower than the values obtained by the non-steady-state methods. For all three electrolytes used in the study, the Electron Diffusion Length was sufficiently high to guarantee ...

  • how efficient is Electron collection in dye sensitized solar cells comparison of different dynamic methods for the determination of the Electron Diffusion Length
    Journal of Physical Chemistry C, 2009
    Co-Authors: Halina K. Dunn, Laurence M. Peter
    Abstract:

    The Diffusion Length of Electrons in high efficiency liquid electrolyte dye-sensitized nanocrystalline solar cells has been investigated using two different approaches. The first method is based on measuring the rise and decay times of the small amplitude photovoltage increment generated by a short laser pulse superimposed on a range of steady-state illumination levels. The advantage of this technique is that it allows the simultaneous measurement of the Diffusion coefficient and Electron lifetime under identical conditions. In addition to transport-controlled substrate charging, direct injection of Electrons into the substrate from dye adsorbed at the contact interface was observed at the high laser pulse energies required for measurements at high dc photovoltages. The second method involves using intensity-modulated photocurrent and photovoltage spectroscopies (IMPS and IMVS, respectively) to measure the Electron Diffusion coefficient and Electron lifetime at short circuit and open circuit, respectively...

  • dye sensitized solar cells based on oriented tio2 nanotube arrays transport trapping and transfer of Electrons
    Journal of the American Chemical Society, 2008
    Co-Authors: James R Jennings, Laurence M. Peter, Andrei Ghicov, Patrik Schmuki, Alison B. Walker
    Abstract:

    Dye-sensitized solar cells fabricated using ordered arrays of titania nanotubes (tube Lengths 5, 10, and 20 μm) grown on titanium have been characterized by a range of experimental methods. The collection efficiency for photoinjected Electrons in the cells is close to 100% under short circuit conditions, even for a 20 μm thick nanotube array. Transport, trapping, and back transfer of Electrons in the nanotube cells have been studied in detail by a range of complementary experimental techniques. Analysis of the experimental results has shown that the Electron Diffusion Length (which depends on the Diffusion coefficient and lifetime of the photoinjected Electrons) is of the order of 100 μm in the titania nanotube cells. This is consistent with the observation that the collection efficiency for Electrons is close to 100%, even for the thickest (20 μm) nanotube films used in the study. The study revealed a substantial discrepancy between the shapes of the Electron trap distributions measured experimentally using charge extraction techniques and those inferred indirectly from transient current and voltage measurements. The discrepancy is resolved by introduction of a numerical factor to account for non-ideal thermodynamic behavior of free Electrons in the nanostructured titania.

Byongcheol Shin - One of the best experts on this subject based on the ideXlab platform.

  • enhanced Electron Diffusion Length of mesoporous tio2 film by using nb2o5 energy barrier for dye sensitized solar cells
    Applied Physics Letters, 2006
    Co-Authors: Moonsung Kang, Byongcheol Shin
    Abstract:

    Electron Diffusion coefficient (D) and Electron lifetime (τ) of mesoporous TiO2 films with Nb2O5 energy barrier were investigated by the stepped light-induced transient measurements of photocurrent and photovoltage, compared with that without the Nb2O5. Both the D and τ values were significantly increased with the Nb2O5 energy barrier, resulting in remarkable enhancements of Electron Diffusion Length and optimum thickness of the TiO2 film. As a result, the Nb2O5 energy barrier could provide much more efficient dye-sensitized solar cells by the additional effect of the improved optimum thickness as well as the existing effect at the same TiO2 film thickness.

  • enhanced Electron Diffusion Length of mesoporous tio2 film by using nb2o5 energy barrier for dye sensitized solar cells
    Applied Physics Letters, 2006
    Co-Authors: Moonsung Kang, Byongcheol Shin
    Abstract:

    Electron Diffusion coefficient (D) and Electron lifetime (τ) of mesoporous TiO2 films with Nb2O5 energy barrier were investigated by the stepped light-induced transient measurements of photocurrent and photovoltage, compared with that without the Nb2O5. Both the D and τ values were significantly increased with the Nb2O5 energy barrier, resulting in remarkable enhancements of Electron Diffusion Length and optimum thickness of the TiO2 film. As a result, the Nb2O5 energy barrier could provide much more efficient dye-sensitized solar cells by the additional effect of the improved optimum thickness as well as the existing effect at the same TiO2 film thickness.

Fernando Ely - One of the best experts on this subject based on the ideXlab platform.

  • revealing lattice and photocarrier dynamics of high quality mapbbr3 single crystals by far infrared reflection and surface photovoltage spectroscopy
    Journal of Applied Physics, 2019
    Co-Authors: Jian Wang, Elaheh Motaharifar, Lakshmi N S Murthy, Marissa Higgins, Diego Barrera, Trey B Daunis, Yangzi Zheng, Anton V Malko, Fernando Ely
    Abstract:

    Hybrid organic-inorganic lead halide perovskite materials show great promise in a number of optoElectronic applications, including solar cells, light emitting diodes, and photodetectors. Understanding their intrinsic material properties is critical to enhancing device performance and enabling innovative material and device designs. Here, we study lattice dynamics using far-infrared (FIR) reflectance and photogenerated carrier dynamics using surface photovoltage (SPV) measurements on high-quality methylammonium lead bromide (MAPbBr3) single crystals. FIR reflectance shows three coherent infrared-active phonon modes between 40 and 200 cm−1 that result in reststrahlen bands with much higher peak reflectance than has been previously reported. The phonon mode strength and damping are comparable to classical oxide perovskite single crystals. However, the effects of defects on photogenerated carrier recombination are still evident in SPV measurements. By performing SPV over different spectral ranges, we are able to separate the effects of surface and bulk defects on the recombination dynamics of photogenerated charge carriers. We further apply SPV measurements to obtain the minority carrier (Electron) Diffusion Length for the MAPbBr3 crystal. This study demonstrates that both FIR reflectance and SPV measurements provide useful information on the electromagnetic response properties of halide perovskite single crystals.

  • revealing lattice and photocarrier dynamics of high quality mapbbr3 single crystals by far infrared reflection and surface photovoltage spectroscopy
    Journal of Applied Physics, 2019
    Co-Authors: Elaheh Motaharifar, Lakshmi N S Murthy, Marissa Higgins, Diego Barrera, Trey B Daunis, Yangzi Zheng, Anton V Malko, Jing Wang, Fernando Ely
    Abstract:

    Hybrid organic-inorganic lead halide perovskite materials show great promise in a number of optoElectronic applications, including solar cells, light emitting diodes, and photodetectors. Understanding their intrinsic material properties is critical to enhancing device performance and enabling innovative material and device designs. Here, we study lattice dynamics using far-infrared (FIR) reflectance and photogenerated carrier dynamics using surface photovoltage (SPV) measurements on high-quality methylammonium lead bromide (MAPbBr3) single crystals. FIR reflectance shows three coherent infrared-active phonon modes between 40 and 200 cm−1 that result in reststrahlen bands with much higher peak reflectance than has been previously reported. The phonon mode strength and damping are comparable to classical oxide perovskite single crystals. However, the effects of defects on photogenerated carrier recombination are still evident in SPV measurements. By performing SPV over different spectral ranges, we are able to separate the effects of surface and bulk defects on the recombination dynamics of photogenerated charge carriers. We further apply SPV measurements to obtain the minority carrier (Electron) Diffusion Length for the MAPbBr3 crystal. This study demonstrates that both FIR reflectance and SPV measurements provide useful information on the electromagnetic response properties of halide perovskite single crystals.Hybrid organic-inorganic lead halide perovskite materials show great promise in a number of optoElectronic applications, including solar cells, light emitting diodes, and photodetectors. Understanding their intrinsic material properties is critical to enhancing device performance and enabling innovative material and device designs. Here, we study lattice dynamics using far-infrared (FIR) reflectance and photogenerated carrier dynamics using surface photovoltage (SPV) measurements on high-quality methylammonium lead bromide (MAPbBr3) single crystals. FIR reflectance shows three coherent infrared-active phonon modes between 40 and 200 cm−1 that result in reststrahlen bands with much higher peak reflectance than has been previously reported. The phonon mode strength and damping are comparable to classical oxide perovskite single crystals. However, the effects of defects on photogenerated carrier recombination are still evident in SPV measurements. By performing SPV over different spectral ranges, we are able...

Moonsung Kang - One of the best experts on this subject based on the ideXlab platform.

  • enhanced Electron Diffusion Length of mesoporous tio2 film by using nb2o5 energy barrier for dye sensitized solar cells
    Applied Physics Letters, 2006
    Co-Authors: Moonsung Kang, Byongcheol Shin
    Abstract:

    Electron Diffusion coefficient (D) and Electron lifetime (τ) of mesoporous TiO2 films with Nb2O5 energy barrier were investigated by the stepped light-induced transient measurements of photocurrent and photovoltage, compared with that without the Nb2O5. Both the D and τ values were significantly increased with the Nb2O5 energy barrier, resulting in remarkable enhancements of Electron Diffusion Length and optimum thickness of the TiO2 film. As a result, the Nb2O5 energy barrier could provide much more efficient dye-sensitized solar cells by the additional effect of the improved optimum thickness as well as the existing effect at the same TiO2 film thickness.

  • enhanced Electron Diffusion Length of mesoporous tio2 film by using nb2o5 energy barrier for dye sensitized solar cells
    Applied Physics Letters, 2006
    Co-Authors: Moonsung Kang, Byongcheol Shin
    Abstract:

    Electron Diffusion coefficient (D) and Electron lifetime (τ) of mesoporous TiO2 films with Nb2O5 energy barrier were investigated by the stepped light-induced transient measurements of photocurrent and photovoltage, compared with that without the Nb2O5. Both the D and τ values were significantly increased with the Nb2O5 energy barrier, resulting in remarkable enhancements of Electron Diffusion Length and optimum thickness of the TiO2 film. As a result, the Nb2O5 energy barrier could provide much more efficient dye-sensitized solar cells by the additional effect of the improved optimum thickness as well as the existing effect at the same TiO2 film thickness.

Jian Wang - One of the best experts on this subject based on the ideXlab platform.

  • revealing lattice and photocarrier dynamics of high quality mapbbr3 single crystals by far infrared reflection and surface photovoltage spectroscopy
    Journal of Applied Physics, 2019
    Co-Authors: Jian Wang, Elaheh Motaharifar, Lakshmi N S Murthy, Marissa Higgins, Diego Barrera, Trey B Daunis, Yangzi Zheng, Anton V Malko, Fernando Ely
    Abstract:

    Hybrid organic-inorganic lead halide perovskite materials show great promise in a number of optoElectronic applications, including solar cells, light emitting diodes, and photodetectors. Understanding their intrinsic material properties is critical to enhancing device performance and enabling innovative material and device designs. Here, we study lattice dynamics using far-infrared (FIR) reflectance and photogenerated carrier dynamics using surface photovoltage (SPV) measurements on high-quality methylammonium lead bromide (MAPbBr3) single crystals. FIR reflectance shows three coherent infrared-active phonon modes between 40 and 200 cm−1 that result in reststrahlen bands with much higher peak reflectance than has been previously reported. The phonon mode strength and damping are comparable to classical oxide perovskite single crystals. However, the effects of defects on photogenerated carrier recombination are still evident in SPV measurements. By performing SPV over different spectral ranges, we are able to separate the effects of surface and bulk defects on the recombination dynamics of photogenerated charge carriers. We further apply SPV measurements to obtain the minority carrier (Electron) Diffusion Length for the MAPbBr3 crystal. This study demonstrates that both FIR reflectance and SPV measurements provide useful information on the electromagnetic response properties of halide perovskite single crystals.