Observation of photo-Seebeck effect in ZnO
When an insulator is illuminated by light that has larger energy than the band-gap energy, electrons in the valence band are excited to the conduction band. Such excited carriers contribute to the electric conduction, known as the photoconduction. However, the fundamental transport property of photo-induced carriers, especially its nature related to thermoelectric transport, is still remaining subject. Here, we investigate the photo-Seebeck effect, which is the Seebeck effect induced by the photo-generated carriers, in the wide-gap conventional semiconductor ZnO for the first time. Our observation can be understood within photo-doping effect to ZnO with induced carrier concentration of about 1019 cm-3. Remarkably, this value is close to the optimized carrier density for thermoelectric materials, suggesting a possible efficient photothermoelectrics in which the carrier concentration is tuned by light, instead of conventional chemical substitution.
This work was supported by Advanced Low Carbon Research and Development Program (ALCA) from JST.
"Photo-Seebeck Effect in ZnO"
by Ryuji Okazaki, Ayaka Horikawa, Yukio Yasui, and Ichiro Terasaki
J. Phys. Soc. Jpn. 81 (2012) 114722.
arXiv:1210.2498.
(Left) Schematic figure for photo-Seebeck Effect. (Right) Variation of the conductivity and the Seebeck coefficient of ZnO by ultraviolet illumination.