AVS 52nd International Symposium
    Thin Films Monday Sessions
       Session TF+EM-MoM

Paper TF+EM-MoM11
Anomalously High Seebeck Coefficient Observed in V@sub 2@O@sub 5@ Thin Films

Monday, October 31, 2005, 11:40 am, Room 306

Session: Thin Films for Photovoltaic and Energy Applications
Presenter: S. Iwanaga, University of Washington
Authors: S. Iwanaga, University of Washington
N.T. Nguyen, University of Washington
R.B. Darling, University of Washington
F.S. Ohuchi, University of Washington
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Vanadium oxides, especially vanadium pentoxide (V@sub 2@O@sub 5@), have gained recent attention for a wide range of applications such as ion storage layers in solid-state batteries, windows for photovoltaic cells, and electro- and photo-chromic devices. Various transport properties have been investigated in the past; however, its thermoelectric properties have not been well characterized. Recently, we observed an anomalously high Seebeck coefficient from sol-gel deposited V@sub 2@O@sub 5@ thin films. Seebeck coefficients of between - 500 to - 700 µV/K were measured, with corresponding electrical conductivities ranging from 0.005 to 0.1 @ohm@@super -1@ cm@super -1@. Unlike conventional materials, the Seebeck coefficients and electrical conductivity act in parallel, suggesting that the carrier concentration increases while maintaining a high Seebeck coefficient. This peculiar transport characteristic appears to be related to polaron hopping. The power generation of the film was further estimated by current-voltage (I-V) measurements to assess the thermoelectric performance of the films. The I-V measurements were performed while applying a temperature gradient to the film by applying a current source in such a way that the thermopower current was suppressed by applying the current in the opposite direction. The I-V characteristics at different applied @DELTA@T were thus obtained, from which the output power (load characteristic, P) was calculated from the I-V data.