Long Vertically Aligned TiO<inf>2</inf> Nanotube Electrodes Prepared via Two-Step Anodization for Highly Efficient Photovoltaics

Jae Yup Kim, Junyoung Shin, Donghwan Kim, Yung Eun Sung, Min Jae Ko

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Vertically aligned long TiO<inf>2</inf> nanotube (NT) electrodes with optimized structures for photovoltaic application were prepared by a two-step anodization method. The structures of the conventional TiO<inf>2</inf> NT electrodes prepared by one-step anodization became severely bundled and disordered for tube lengths exceeding 20 μm. On the other hand, two-step anodization resulted in uniform and bundle-free TiO<inf>2</inf> NT electrodes, with tube lengths of up to 38 μm. When used in dye-sensitized solar cells (DSSCs) as photoanodes, the two-step TiO<inf>2</inf> NT electrodes exhibited enhanced short-circuit current density (J<inf>sc</inf>) with increasing tube length, owing to an increased roughness factor, which resulted in high dye loading. However, the dark current and open-circuit voltage decay (OCVD) curves confirmed that the electron recombination rate increased, and the electron lifetime decreased, with increasing tube length. This reduced electron lifetime resulted in sharp reductions in the open-circuit voltage (V<inf>oc</inf>) with increasing tube length. Owing to the trade-off between the enhanced current density and the reduced electron lifetime, an optimal conversion efficiency of 4.56 % was obtained for a tube length of 29 μm.

Original languageEnglish
Pages (from-to)1030-1040
Number of pages11
JournalIsrael Journal of Chemistry
Volume55
Issue number9
DOIs
Publication statusPublished - 2015 Sep 1

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Keywords

  • anodization
  • dye-sensitized solar cells
  • electron lifetime
  • nanotubes
  • titanium

ASJC Scopus subject areas

  • Chemistry(all)

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