Cu-In-Ga-Se Nanoparticle Colloids as Spray Deposition Precursors for Cu(In,Ga)Se2 Solar Cell Materials

The use of nanoparticle colloids for spray deposition of Cu(In,Ga)Se2 (CIGS) precursor films and subsequent fabrication of CIGS solar cells has been investigated. According to this approach, amorphous Cu-In-Ga-Se nanoparticle colloids were first prepared by reacting a mixture of CuI, InI3, and GaI3 in pyridine with Na2Se in methanol at reduced temperature. Purified colloid was sprayed onto heatedmolybdenum-coated sodalime glass substrates to form Cu-In-Ga-Se precursor films. After thermal processing of the precursor films under a selenium ambient, CIGS solar cells were fabricated. Cu-In-Ga-Se colloids and films were characterized by inductively coupled plasma atomic emission spectroscopy, thermogravimetric analysis, transmission electron microscopy, x-ray diffraction, scanning electronmicroscopy, and Auger electron spectroscopy. Standard current voltage characterization was performed on the CIGS solar cell devices with the best film exhibiting a solar conversion efficiency of 4.6%.