Innovative materials and quantum structures are required to increase the efficiency of PV cells. Beyond Si quantum dots (QD), Ge nanostructures begin to attract a growing attention because of lower melting point and energy gap with respect to Si. Moreover, the larger excitons Bohr radius in Ge (~ 20 nm, quadruple than in Si) would permit to exploit the confinement effect at a larger size with respect to Si.Recently, Ge QDs embedded in SiO2 have been realized by deposition of a SiGeO alloy layer (by magnetron co-sputtering) followed by thermal annealing up to 800 C. Such Ge QDs showed an optical bandgap of 1.6 eV, well higher than that of not-confined Ge (~ 0.7 eV), but independent of the QDs size [1]. At the same time, a strong relation between the QDs size and the absorption probability has been evidenced, pointing out that the photon absorption can be mediated by electronic states localized at the surface …