Conversion efficiency of resonant cavity enhanced narrow bandgap interband cascade photovoltaic cells

Abstract

By combining an interband cascade (IC) configuration with an optical cavity, a novel approach to achieve efficient narrow bandgap photovoltaic (PV) cells is proposed. The proposed resonant cavity enhanced (RCE) ICPV cells can significantly alleviate the challenging issues in narrow bandgap semiconductor materials, which include a small absorption coefficient, a short diffusion length, and a high dark current density. Through simulations with realistic material parameters based on InAs/GaSb superlattice heterostructures, RCE ICPV cells are capable of achieving a conversion efficiency that exceeds 60%, which is much higher than what can be achieved with any other approach, especially with materials of a bandgap smaller than 0.3 eV. By varying structure parameters such as the absorber thickness, number of cascade stages, and the top mirror reflectance, we demonstrate how an RCE ICPV cell can be constructed to achieve an optimized device performance with high conversion efficiency. Also, a design example of a practical RCE narrow bandgap ICPV cell is provided.