III-V-N materials for super high-efficiency multijunction solar cells

Abstract

We have been studying concentrator multi-junction solar cells under Japanese Innovative Photovoltaic R&D program since FY2008. InGaAsN is one of appropriate materials for 4- or 5-junction solar cell configuration because this material can be lattice-matched to GaAs and Ge substrates. However, present InGaAsN single-junction solar cells have been inefficient because of low minority-carrier lifetime due to N-related recombination centers and low carrier mobility due to alloy scattering and non-homogeneity of N. This paper presents our major results in the understanding of majority and minority carrier traps in GaAsN grown by chemical beam epitaxy and their relationships with the poor electrical properties of the materials. © 2012 American Institute of Physics.