  In a recent article [Phys. Rev. Applied 5, 024005 (2016)], Gibelli and
coworkers proposed a method to determine the thermopower, i.e. the Seebeck
coefficient, using photoluminescence measurements. The photoluminescence
spectra are used to obtain the local gradients of both the electrochemical
potential difference between electron and holes and the temperature of the
electron-hole plasma. However, the definition of the thermopower given in that
article seems erroneous due to a confusion between the different physical
quantities needed to derive this parameter.
