Electrostatic spray-deposited CuInGaSe2 nanoparticles: Effects of precursors' Ohnesorge number, substrate temperature, and flowrate on thin film characteristics

The effect of precursor viscosity, substrate temperature, and flow rate on CuInGaSe2 nanoparticle-based thin films deposited by an electrostatic spray deposition (ESD) technique are studied. ESD is superior to pneumatic spraying because it produces nano-scale, self-dispersive (non-agglomerating), highly wettable (electrowetting) and adhesive droplets, which collectively yield a uniform coating on the substrate. The synthesized CuInGaSe2 nanoparticles were added to 4 different solvents: ethanol (E), butyl carbitol (BC), ethylene glycol (EG), and diethylene glycol (DEG). Subsequently, the solvents were electrostatically sprayed onto a molybdenum-coated soda-lime glass substrate. The solvent that yielded the most uniform surface morphology for the coated materials was identified. The surface roughness of the coated CIGS thin film, which depends on viscosity and the substrate temperature, was studied by AFM characterization.

► The effect of solvent viscosity on dispersion of CIGS nanoparticles is investigated. ► At the highest substrate temperature, drops evaporated before they reach the substrate. ► Voids among particles increased porosity at elevated substrate temperatures. ► At low substrate temperatures, evaporation was slow and wetting was excessive.