Copper Indium Selenide Solar Cells Fabricated from Electrodeposited Copper/Indium Multi-Stacked Precursors and a Three-Step Selenization Process

Abstract

Stoichiometric CuInSe2 chalcopyrite photoabsorbers have been synthesized using multi-bath electrodeposition and a three-step selenization process with non-toxic selenium pellets. Among many approaches used to prepare Cu-In metal precursors, multi-stacked electrodeposition is a promising method because of its low-cost process, easy control of the thickness ratio of the Cu-In metal layers, efficient usage of resources, and large-scale mass production. In this study, copper (Cu) and indium (In) metallic precursors with an appropriate thickness ratio were fabricated on Mo/SLG (soda-lime glass). The selenization process was completed in selenium (Se)rich atmosphere at three different temperatures in sequence (120, 350, and 550 degrees C). Unlike the conventional two-step approach, which has adhesion problems, the CuInSe2 films exhibited a relatively smooth and dense morphology with large, well-crystallized grains after selenization and potassium cyanide etching. The thermal treatment at 120 degrees C resulted in intermetallic Cu-In alloys and suppressed excessive vaporization of metallic In and the formation of Kirkendall voids. The CuInSe2 solar cell with a structure of Ni-Al grid/ZnO:Al/i-ZnO/n-CdS/p-CuInSe2/Mo/SLG showed a cell efficiency exceeding 5%.