The use of convex lens as primary concentrator for multi-junction solar cells Juan Paolo Lorenzo Gerardo Barrios, John Raffy Cortez, Gene Michael Herman, Aris Larroder, Bernice Mae Yu Jeco, Kentaroh Watanabe and Yoshitaka Okada Emergent Scientist, 2 (2018) 5 Published online: 23 November 2018 DOI: 10.1051/emsci/2018004