Usually, the presence of grain-boundaries (GBs) degrades solar-cell device performance due to defects and impurities that segregate there, creating in-gap electronic states that lead to enhanced recombination of photo-excited electron-hole pairs. However, in solar-cells comprising a polycrystalline Cu(In1-x,Gax)Se2 thin-film absorber, with x < 0.4, it seems that the presence of GBs does not harm the device performance and may even help improving it, achieving efficiencies of more than 21%. In order to understand this surprising phenomenon we investigated the electronic properties around GBs of polycrystalline Cu(In1-x,Gax)Se2 films as a function of Ga content, using scanning tunneling spectroscopy and conductance atomic force microscopy. Data acquired on samples with low Ga content (x = 0 and 0.33) reveal downward band-bending with respect to adjacent p-type grains, suggesting type inversion at the surface of GBs. This behavior increases the collection efficiency of the photo-generated charges. Such a behavior was not observed for samples for high Ga contents (x > 0.5). Furthermore, in the low-x regime we observed reduced deep-level density of states, resulting in reduced recombination rate. Our results thus shed light the origin of the x-dependent efficiency for polycrystalline Cu(In1-x,Gax)Se2 based solar cells and contribute to solving the puzzle regarding their high conversion efficiency. We further investigated the effect of Na-doping on the electronic properties of polycrystalline Cu(In0.7,Ga0.3)Se2 thin films. Our results show correlation between the presence of Na and reduced density of deep-level states at GBs that can explain the beneficial effect of Na doping and the benign behavior of the GBs.