Trap-Free Transport in Ordered and Disordered TiO2 Nanostructures

Julio Villanueva-Cab, Song Rim Jang, Adam F. Halverson, Kai Zhu, Arthur J. Frank

Research output: Contribution to journalArticlepeer-review

63 Scopus Citations

Abstract

Understanding the influence of different film structures on electron diffusion in nanoporous metal oxide films has been challenging. Because of the rate-limiting role that traps play in controlling the transport properties, the structural effects of different film architectures are largely obscured or reduced. We describe a general approach to probe the impact of structural order and disorder on the charge-carrier dynamics without the interference of transport-limiting traps. As an illustration of this approach, we explore the consequences of trap-free diffusion in vertically aligned nanotube structures and random nanoparticle networks in sensitized titanium dioxide solar cells. Values of the electron diffusion coefficients in the nanotubes approached those observed for the single crystal and were up to 2 orders of magnitude greater than those measured for nanoparticle films with various average crystallites sizes. Transport measurements together with modeling show that electron scattering at grain boundaries in particle networks limits trap-free diffusion. In presence of traps, transport was 103-105 times slower in nanoparticle films than in the single crystal. Understanding the link between structure and carrier dynamics is important for systematically altering and eventually controlling the electronic properties of nanoscaled materials.

Original languageAmerican English
Pages (from-to)2305-2309
Number of pages5
JournalNano Letters
Volume14
Issue number5
DOIs
StatePublished - 14 May 2014

NREL Publication Number

  • NREL/JA-5900-60140

Keywords

  • dye-sensitized solar cells
  • electron scattering
  • grain boundaries
  • Trap-free transport

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