Modulated photoluminescence as an effective lifetime measurement method: Application to a-Si:H/c-Si heterojunction solar cells

Solar cells made of heterojunctions between hydrogenated amorphous silicon (a-Si:H) thin films and crystalline silicon (c-Si) require good passivation of both front and back surface defects of the crystalline silicon wafers and low recombination at the interfaces. A good indicator of the interface quality is given by the effective lifetime that can be deduced from a modulated photoluminescence (MPL) technique by recording the frequency dependence of the photoluminescence phase shift with respect to the time-modulated light excitation. We apply the MPL technique to assess the passivation quality of different kinds of amorphous layers, for both p- and n-type silicon wafers as well as their evolution upon annealing. The MPL effective lifetimes are also compared to those deduced from the photoconductance technique.