In this paper we introduce a novel method for obtaining the capacitance-voltage (C-V) characteristics of non-ideal p-n junction solar cells. The method is based on the analysis of the measured frequency dependence of the sample's impedance Z ("Z analysis method"). The method is tested on ideal Si wafer devices and then transferred to non-ideal devices (ALICIA polycrystalline silicon thin-film solar cells on glass). It is shown that impedance analysis yields easily interpretable results and reliable values for the doping density and the junction built-in potential, for both ideal and non-ideal p-n junction diodes. Using the impedance analysis method, the influence of rapid thermal annealing (RTA) and hydrogenation on the active base doping density of ALICIA solar cells isinvestigated and discussed. From temperature dependent Z analysis it can be concluded that donor- and acceptor-likedefects have a strong impact on the free carrier density in the lowly doped base region.
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