A method for determining the thermal donor concentration of a test sample made of a semiconductor material, includes providing a reference sample made of the same semiconductor material and having a known thermal donor concentration; measuring a photoluminescence signal of the reference sample for a photon energy comprised between 0.65 eV and 0.8 eV, the photoluminescence signal of the reference sample exhibiting an intensity peak in a photon energy range of 0.65 eV to 0.8 eV; determining, from the photoluminescence signal, an experimental relationship between the thermal donor concentration and a parameter representative of the intensity peak; measuring a photoluminescence signal of the test sample for at least one photon energy comprised between 0.65 eV and 0.8 eV; determining from the photoluminescence signal a specific value of the parameter; and determining the thermal donor concentration from the specific value of the parameter by using the experimental relationship.