Improved Efficiency of CuInS₂-Based Solar Cells without Potassium Cyanide Process

Abstract

A high open-circuit voltage ( V oc ) exceeding 0.80 V was obtained by adding Ga to Na-incorporated CuInS 2 thin films. Cu(In, Ga)S 2 films were fabricated by sulfurization of Na-containing Cu-In-Ga precursors in H 2 S atmosphere. The inclining Ga profile resulted in a graded band gap. Therefore, the enhancements of cell performance by Ga addition were not only increase in Voc but also that in short-circuit current density ( J sc ). We achieved an efficiency of 11.2% with V oc =0.802 V, J sc =20.9 mA/cm 2 and FF=0.667. This is the highest efficiency reported for CuInS 2 solar cells fabricated without the potassium cyanide (KCN) process.