Titanium dioxide antireflection coating for silicon solar cells by spray deposition

A high-speed production process is described for depositing a single-layer, quarter-wavelength thick anti-reflection coating of titanium dioxide on metal-patterned single-crystal silicon solar cells for terrestrial applications. Controlled atomization spraying of an organo-titanium solution was selected as the most cost-effective method of film deposition using commercial automated equipment. The optimal composition consists of titanium isopropoxide as the titanium source, eta-butyl acetate as the diluent solvent, sec-butanol as the leveling agent, and 2-ethyl-1-hexanol to render the material uniformly depositable. Application of the process to the coating of circular, large-diameter solar cells with either screenprinted silver metallization or with vacuum-evaporated Ti/Pd/Ag metallization showed increases of over 40% in electrical-conversion efficiency. Optical characteristics, corrosion resistance, and several other important properties of the spray-deposited film are reported. Experimental evidence is presented that indicates a wide tolerance in the coating thickness upon the overall efficiency of the cell. In addition, considerations pertaining to the optimization of anti-reflection coatings in general are discussed and a comprehensive critical survey of the literature is presented. 66 references.