Spherical Si solar cell, which is made up of Si spheres with a diameter of approximately 1.0mm, is expected to be a promising candidate for low consumption of Si feedstock and simple process technology. This paper describes the formation process and the structure of a concentrator module in detail. The concentrator lens was formed by casting with ultraviolet light hardening resin. The concentration ratio was 4.4 times and the pitch between the spheres was 2.0mm. By this module design, it was possible to realize a consumption of the Si feedstock of about 3.0g/W. Conversion efficiencies of 11.3% from single-sphere cell, 8.5% from a 23-spheres module and 5.2% from a 105-spheres module under AM 1.5, 100 mW/cm(2) illumination were achieved. (c) 2007 Elsevier B.V. All rights reserved.