The implementation of potassium fluoride treatments as a doping and surface modification procedure in chalcopyrite absorber preparation has recently gained much interest since it led to new record efficiencies for this kind of solar cells. In the present work, Cu In,Ga Se 2 absorbers have been evaporated on alkali containing Mo soda lime glass substrates. We report on compositional and electronic changes of the Cu In,Ga Se 2 absorber surface as a result of a post deposition treatment with KF KF PDT . In particular, by comparing standard X ray photoelectron spectroscopy and synchrotron based hard X ray photoelectron spectroscopy HAXPES , we are able to confirm a strong Cu depletion in the absorbers after the KF PDT which is limited to the very near surface region. As a result of the Cu depletion, we find a change of the valence band structure and a shift of the valence band onset by approximately 0.4 eV to lower binding energies which is tentatively explained by a band gap widening as expected for Cu deficient compounds. The KF PDT increased the open circuit voltage by 60 70 mV compared to the untreated absorbers, while the fill factor deteriorated