GaNAsSb 1-eV solar cells for use in lattice-matched multi-junction architectures

Photovoltaic devices made from a dilute nitride material, GaAsNSb, with band-gap close to 1eV have been developed and characterised. Homojunction devices of n-on-p and p-on-n type as well as an n-on-p GaAs/GaNAsSb heterojunction have been grown by molecular beam epitaxy. Optical and electrical characteristics are reported and a one-dimensional drift-diffusion model of internal quantum efficiency is used to estimate minority carrier diffusion lengths. The GaAs/GaNAsSb heterostructure produced AM1.5G short-circuit current of 23.6 mA/cm
²
, open-circuit voltage of 0.44V and fill factor of 67%. The model suggests that this performance is limited by both diffusion length and surface recombination.