AVS 61st International Symposium & Exhibition
    Electronic Materials and Processing Thursday Sessions
       Session EM2-ThA

Paper EM2-ThA8
Role of Light Scattering in Hybrid Solar Cells

Thursday, November 13, 2014, 4:40 pm, Room 314

Session: Hybrid and Organic Electronics
Presenter: James Dorman, University of Konstanz, Germany
Authors: J. Dorman, University of Konstanz, Germany
M. Noebels, University of Konstanz, Germany
T. Pfadler, University of Konstanz, Germany
J. Weickert, University of Konstanz, Germany
L. Schmidt-Mende, University of Konstanz, Germany
Correspondent: Click to Email
Hybrid solar cells, with an inorganic/organic interface for charge separation, have been extensively investigated in the past decade in order to replace the expensive Si based technology with an inexpensive alternative. Typically, these devices incorporate a mesoporous TiO2 film which is decorated with dye molecules and filled with a hole transport material, to conduct the electrons and holes, respectively. Recently, devices with an liquid electrolyte have been able to reach up to 13% conversion efficiency. However, the TiO2 mesoporous films used for solid state dye sensitized solar cells and hybrid solar cells have a limited light absorption due to thickness of the film (500 nm – 2 µm) required for efficient charge transportation. An elegant approach to increase the light absorption is to induce “defects” within the mesoporous film, causing light to scatter within the active layer of the device. In this work, we combine the commonly used 25 nm particles with other nanostructures, including 200 nm TiO2 particles, TiO2 nanowires, and Sn doped nanowires, all of which produce light scattering due to their dimensions and disorder within the active layer. Through this approach, we are able to correlate an improvement in conversion efficiencies of around 25 % to the light scattering. Furthermore, the incorporation of these nanowire structures increases the mobility of the electrons, allowing for increased charge extraction and reduced recombination. These two phenomena can be simultaneously engineering due to the crystallinity of the “defects” within the films and the cascading conduction bands produced with the incorporation of the doped TiO2 wires. The extent of the reduction in recombination is quantified through photovoltage decay and impedance spectroscopy measurements and compared to the standard mesoporous TiO2 devices.