Improvement of the Electrochemical Profiling Technique of Carrier Concentration in Cu(InGa)Se2 Thin Film Solar Cells

Abstract

In our previous works, we measured the carrier concentration profile of Cu(InGa)Se2 (CIGS) films using the electrochemical capacitance–voltage (ECV) method with ethylenediaminetetraacetic acid (EDTA). However, we occasionally observed deposition of Se onto the CIGS films after the etching, which limited the reproducibility of the measurement. In this study, we tried to improve the ECV technique and successfully measured the carrier concentration profile for the film with a wide Cu/III ratio range by the addition of sulfurous acid into the EDTA electrolyte. Moreover, the results of these measurements revealed that the carrier (hole) concentrations of the CIGS films ranged between 1016 and 1018 cm-3 and that the carrier concentration changed with the growth conditions. Based on the above results, it is believed that this new measurement technique is a useful and powerful tool for characterization of CIGS thin films.