GaInN/GaN - Ni/Au transparent conducting oxide Schottky barrier solar cells

Schottky barrier solar cells made from two different GaInN/GaN material structures combined with Ni/Au transparent conducting oxide films are demonstrated herein. The GaInN/GaN multiple quantum well structure has a short-circuit current density of 0.062 mA/cm², open-circuit voltage of 0.468 V, and fill-factor of 69.8%. The GaInN/GaN double-heterostructure exhibits a 51% reduction in short-circuit current density, 47% lower open-circuit voltage, and 27% smaller fill-factor. Preliminary computer simulations indicate that a 10-fold increase in short-circuit current density should be possible for the GaInN/GaN multiple quantum well structure. The Ni/Au layer is responsible for some of this shortfall as its optical transparency varies from a low of 46.4% at 300 nm to a high of 76.8% at 500 nm. There is also evidence that photo-generated carriers are not being collected from the entire illuminated device area. The Ni/Au bi-layer has an electrical resistivity of 2.9 × 10^-5 Ωcm, but it is very thin and no effort has been made to trade-off its electrical behavior against its optical properties. Work is now underway to increase the open-circuit voltage of these devices by adopting “barrier height enhancement” schemes.