Authors: R. Jose, P.S. Archana, A. Le Viet, E. Naveen Kumar. M.M. Yusoff, S. Ramakrishna
Affilation: Universiti Malaysia Pahang, Malaysia
Pages: 775 - 778
Keywords: nanowires, electron diffusion coefficient, transient photocurrents, impedance spectroscopy
Polymeric solutions containing precursors of wide bandgap metal oxide semiconductors were electrospun either directly on a transparent conducting glass substrate or on other sample collectors to prepare their films. These films produced randomly oriented continuous nanostructures of the respective metal oxides with controlled aspect ratio from continuous nanofibers to short nanorods on annealing. Dye-sensitized solar cells of high photovoltaic conversion efficiencies were fabricated using these metal oxide films. The charge transport through those devices was studied by electrochemical impedance spectroscopy and transient photocurrent measurements. Continuous nanofibers had longer charge collecting times and short nanorods have enhanced scattering losses. We show that metal oxide films containing random network of nanowires aspect ratio 10:1 can have an order of magnitude higher diffusion coefficient than other morphologies owing to their larger diffusion lengths. Conventionally the enhanced diffusion was achieved by ordered nanowire arrays, which are hardly scalable for practical purposes. We show that similar diffusion could be achieved in the random network also thereby providing an opportunity to build dye-sensitized solar cells using cost effective and scalable methods. We further increased the diffusion coefficient in random metal oxide nanowire network by appropriate doping.