Improvement of the Electrical Properties of Cu-Poor CuInS₂ Thin Films by Sodium Incorporation

Abstract

We investigated the effects of intentional sodium incorporation on the electrical conductivity of Cu-poor CuInS 2 thin films. CuInS 2 films were fabricated by sulfurization of In–S/Cu/Na 2 S/In precursors. Sodium incorporation resulted in a remarkable increase in the lateral conductivity and the cell efficiency of CuInS 2 -based solar cells. Photoluminescence measurements revealed that the enhancements were attributed to the annihilation of donor states, most likely In interstitials, by sodium incorporation.