Berlin 2012 – scientific programme

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DS: Fachverband Dünne Schichten

DS 44: Poster IV: Thin film photovoltaics; Organic electronics and photovoltaics (jointly with CPP, HL, O); Organic thin films; Trends in atomic layer deposition (Focused session)

DS 44.2: Poster

Friday, March 30, 2012, 09:30–12:00, Poster E

Inhomogeneities in charge carrier transport properties of Cu(In,Ga)Se₂ solar-cells — •Melanie Nichterwitz¹, Christian Kaufmann¹, Raquel Caballero², Hans-Werner Schock¹, and Thomas Unold¹ — ¹Helmholtz-Zentrum Berlin, Germany — ²Universidad Autónoma de Madrid, Spain

In this study, electron beam induced current (EBIC) in the cross section configuration is used to characterize charge carrier transport in Cu(In,Ga)Se₂ (CIGSe)/CdS/ZnO solar-cells. It is shown that charge carrier transport properties are (i) generation dependent and (ii) grain specific, i.e. spatially inhomogeneous. Within some grains of the CIGSe absorber layer, the collected short circuit current is reduced significantly for electron beam irradiation such that there is no generation at the heterojunction. Charge carrier transport is generation dependent in these grains for all used electron beam currents, i.e. generation densities (low injection). In other grains however, charge carrier transport is only generation dependent for the highest used electron beam current. In conjunction with numerical simulations, these results are used to derive a model for the electronic band diagram of the heterojunction region of the solar cell. It is based on the assumption of (i) a thin layer with a high density (≈ 10¹⁷ cm⁻³) of deep acceptor type defect states (p+ layer) and a lowered valence band maximum between the CIGSe and the CdS layer and (ii) donor type interface states at the p+ layer/CdS interface of some grains.