  Spectroscopic techniques, including photoelectron spectroscopy, diffuse
reflectance, and x-ray absorption, are used to investigate the electronic
structure and the local structure of LaOBiS$_{2-x}$Se$_x$ thermoelectric
material. It is found that Se substitution effectively suppresses local
distortion, that can be responsible for the increased carrier mobility together
with a change in the electronic structure. The results suggest a possible way
to control thermoelectric properties by tuning of the local crystal structure
of these materials.
