▎ 摘　　要

We theoretically investigate the possibility of multiple exciton-generation in graphene nanostructures using tight-binding calculations. We show that multiple-exciton generation occurs in graphene nanoribbons with armchair edges wherein the efficiency of photoelectric conversion exceeds 100%. From first-principles calculations, we demonstrate that the graphene-diamond hybrid structure is a possible and robust nanostructure that can achieve multiple-exciton generation. (C) 2013 The Japan Society of Applied Physics