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Influence of Nitrogen Doping on Tungsten Oxide Thin Films for Photoelectrochemical Water Splitting

Published online by Cambridge University Press:  26 February 2011

Brian Cole ,
Bjorn Marsen  and
Eric Miller
Brian Cole
Affiliation:
bcole@hawaii.edu, University of Hawaii at Manoa, Hawaii Natural Energy Institute, 1680 East West Road, POST 109, Honolulu, HI, 96822, United States, 808-956-5229
Bjorn Marsen
Affiliation:
marsen@hawaii.edu, University of Hawaii, Hawaii Natural Energy Institute, 1680 East West Road, POST 109, Honolulu, HI, 96822, United States
Eric Miller
Affiliation:
ericm@hawaii.edu, University of Hawaii, Hawaii Natural Energy Institute, 1680 East West Road, POST 109, Honolulu, HI, 96822, United States
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Abstract

Thin films of tungsten oxide were investigated for use as a top junction in a hybrid photoelectrode. To increase the solar to hydrogen efficiency, the tungsten oxide requires a bandgap reduction to the range of 2.2 to 2.4 eV. Nitrogen doping of WO3 films was employed to reduce the bandgap via valence band modification. For low levels of doping, the bandgap was observed to increase, an effect attributed to decreased size of the polycrystals in the film. The photoelectrochemical efficiency was found to decrease from 80% for pure WO3 to 56% for films deposited at a nitrogen partial pressure of 1.5 mTorr. For even higher doping levels (to 5 mTorr N2), the bandgap was shown to decrease to a value of ∼1.9 eV, but the structural data indicates that significant disorder had been introduced. This disorder is consistent with recurrent dislocations, an effect that is common for the tungsten oxide material.

Keywords

thin filmoptical propertiesphotochemical
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 974: Symposium CC – Solar Energy Conversion , 2006 , 0974-CC09-04
Copyright
Copyright © Materials Research Society 2007

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