CIGS films via nanoparticle spray deposition: attempts at densifying a porous precursor

This report summarizes our efforts to produce large-grained CIGS materials from porous nanoparticle precursor films. In our approach, a nanoparticle colloid is first prepared via low-temperature solution synthesis. Next, a thin precursor film is prepared by spray deposition of this colloid onto a heated substrate. Post-processing of these precursors is performed to induce phase formation and grain growth. Various colloids have been sprayed onto substrates such as molybdenum/glass and CdS/SnO₂/glass. Post-processing treatments under controlled gas ambients have been performed according to both standard and rapid-thermal annealing (RTA) approaches. Morphology, phase formation, and chemical composition of these nanoparticle-derived films have been characterized using SEM, XRD, Raman, and AES. Although the majority of the approaches employed did not produce large-grained materials, CIGS colloid sprayed onto CdS/SnO₂ /glass substrates heated at 225°C produced films with a dense morphology as-deposited