Characterization of CIGS grain boundaries using Atom Probe Tomography

Summary form only given. Polycrystalline thin-film solar cells based on the compound semiconductor Cu(In, Ga)Se₂ (CIGS) as absorber materials are important for photovoltaic applications because of their high energy conversion efficiency, long-term stable performance, and low-cost production. The atomic-scale elemental distribution within the absorber layer has remained largely unknown although it is expected to control the electronic and photovoltaic properties of CIGS solar cells. This work gives an insight into the three-dimensional elemental distribution in some CIGS solar cells using Pulsed Laser Atom Probe Tomography. We focus on the concentration and distribution of impurities, namely Na and O, in the CIGS layer. These atoms are found to diffuse from the soda lime glass substrate into the absorber layer. Based on the experimental observations, we propose that passivation of grain boundary defects by Na and O play an important role in enhancing the efficiency of CI(G)S solar cells.