High Efficiency InGaN Solar Cells

Indium gallium nitride (InGaN) has the potential of forming optoelectronic devices – including solar cells – covering a range of 0.7 eV to 3.4 eV. This energy range matches closely the usable emission present in the solar spectrum as seen from space (AM0). Beside the inherent thermal ruggedness of the III Nitrides which make them fit for high temperature applications such as in solar cells used in high terrestrial concentrator systems, it has recently been determined that these Nitride materials can offer exceptional radiation tolerance that is well beyond what can be achieved with conventional solar cell materials that are currently flown into space. Although InGaN as a solar cell would be a less mature technology than other III-V semiconductors, and hence will not likely have as high efficiency as its III-V counterparts, the important factor is that it will degrade far less over the its lifetime. Two critical issues need to be addressed for the realization of InGaN-based multijunction solar cells, namely adequate minority carrier lifetimes and high p-type doping. A key to a monolithically integrated InxGa1-xN multijunction solar cell is the availability of a crystallographically compatible tunnel diode whose feasibility will be investigated.