  We report the observation of photo-Seebeck effect in tetragonal PbO crystals.
The photo-induced carriers contribute to the transport phenomena, and
consequently the electrical conductivity increases and the Seebeck coefficient
decreases with increasing photon flux density. A parallel-circuit model is used
to evaluate the actual contributions of photo-excited carriers from the
measured transport data. The photo-induced carrier concentration estimated from
the Seebeck coefficient increases almost linearly with increasing photon flux
density, indicating a successful photo-doping effect on the thermoelectric
property. The mobility decreases by illumination but the reduction rate
strongly depends on the illuminated photon energy. Possible mechanisms of such
photon-energy-dependent mobility are discussed.
