Thin Film Calorimetry as a Tool for in-situ Investigation of Reactions in the Cu-In-Se Ternary System

Selenization of Cu-In-precursor films is regarded as one of the most promising techniques to produce polycrystalline CuInSe₂ (CIS) absorber layers for thin film solar cells. Although it is well known that the formation of the ternary compound proceeds via intermediate binary Cu-Se and In-Se phases former examinations are restricted to ex-situ X-ray diffraction studies after a specific annealing program. Applying the Differential Scanning Calorimetry (DSC) to thin films with a thickness of practical interest (1–3 µm) we are able to monitor the reactions of Cu-In-Se-sandwiches in-situ during the heating cycle and to characterize them by their onset temperature and enthalpy.

In this contribution we demonstrate the potential of Thin Film Calorimetry (TFC). Binary and ternary layers of Cu-In-Se were analysed, the corresponding signals are discussed in terms of phase formation and equilibrium diagrams.