Lifetime Enhancement of Visible Light Induced Photocharges in Tungsten and Nitrogen in situ Codoped TiO2:WN Thin Films

Steven Johnston, N. Delegan, R. Pandiyan, A. Dirany, S. Komtchou, P. Drogui, M. El Khakani

Research output: Contribution to journalArticlepeer-review

15 Scopus Citations


We report on one-step in situ codoped TiO2 thin films synthesized by cosputtering. The purpose of this acceptor-donor passivated codoping approach is to overcome the optoelectronic limitations that arise for monodoped TiO2 in photocatalytic applications. To evaluate these added benefits, the TiO2:WN thin films were characterized by different techniques. X-ray diffraction patterns and X-ray photoelectron spectral analysis revealed that both N and W dopants are mostly present in the desired substitutional locations. Additionally, the codoping approach was found to reduce the internal strain and defect density of the TiO2:WN films as compared to their monodoped TiO2:N counterparts. This defect reduction is confirmed via photocharge lifetime variation obtained using visible light flash photolysis time-resolved microwave conductivity measurements (FP-TRMC). Photocharge lifetime analysis indicated the presence of three distinct decay processes: charge trapping, recombination, and surface reactions. These characteristic lifetimes of the codoped TiO2:WN films (i.e., 0.08, 0.75, and 11.5 μs, respectively) were found to be about double those of their nitrogen monodoped TiO2:N counterparts (i.e., 0.03, 0.35, and 6.8 μs), quantitatively confirming the effective passivating outcome of the tungsten-nitrogen codoping approach developed here. The practicality of this method was confirmed by integrating the TiO2:WN films as photoanodes for the electro-photocatalytic, solar light driven degradation of a real pollutant (i.e., atrazine). A significant increase in the degradation kinetics, leading to a 4-fold increase in the pseudo-first-order degradation constant for the optimally doped TiO2:WN photoanodes (0.106 min-1) from the undoped TiO2-x ones (0.026 min-1), is a direct consequence of the increased photocharge lifetimes in tandem with visible light photosensitivity.

Original languageAmerican English
Pages (from-to)5411-5419
Number of pages9
JournalJournal of Physical Chemistry C
Issue number10
StatePublished - 2018

Bibliographical note

Publisher Copyright:
© 2018 American Chemical Society.

NREL Publication Number

  • NREL/JA-5K00-72060


  • doping
  • optoelectronics
  • sputtering
  • thin films


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