Electrical resistance measurements were evaluated as a method to study phase transformations and reactions during thermal processing of metallic thin film precursors for chalcopyrite solar cells. The CuInSe2 (CIS) absorbers were formed by the stacked elemental layer (SEL) process. Pure Cu films were investigated, as well as sequentially evaporated Cu-In and Cu-Ga thin film stacks. According to Kissinger the activation energy of a chemical reaction can be determined by evaluating the temperature of maximum reaction rate depending on the (constant) heating rate of the samples. The Kissinger-evaluation of the activation energy of the Cu11In9 formation derived from the resistance measurements in this work was in good match with prior calorimetric results. The speed of the electric measurements (up to 50/s) was high enough to resolve even fast melting reactions. Very slow reactions could be measured reproducibly. Variations in the temperature-dependent behaviour of different samples could be correlated to the influence of the precursor morphology on the reaction kinetics; i.e. the dewetting of an elemental layer in the precursor led to a higher diffusion length, and therefore, delayed reactions. The substrate temperature during Cu-deposition had an influence on the Cu-Ga reaction kinetics. To conclude, electric resistance measurements during the thermal processing of thin film SEL-precursors could serve to determine kinetic parameters and to analyse the influence of different deposition processes on the reaction behaviour. (C) 2003 Elsevier Science B.V. All rights reserved.