Indium-Phosphide Solar Cells on Silicon Substrates
Indium-Phosphide Solar Cells on Silicon
Bedford, MA 01730
Stanley M. Vernon (617-275-6000)
LeRC -- NAS3-25283
Growth of indium-phosphide photovoltaic cells on silicon substrates avoids the
use of InP as a substrate and could drastically reduce the cost and weight of InP
cells. The inherent radiation resistance of InP may result in a higher end-of-life
efficiency than can be achieved with silicon as the active material. Although the
eight percent difference in crystal lattice spacing is expected to result in some
loss of efficiency due to the formation of dislocations, a number of techniques show
some promise for reducing the dislocation density, based on recent work with gallium-arsenide.
Phase I demonstrated the feasibility of InP-on-Si solar cells, showing that the
hetero-epitaxial growth procedures developed for GaAs-on-Si can be used there and
that only minor changes from the previously developed InP-on-InP cell fabrication
process are needed. The work also gave a measure of the defect densities which occur
in the material and how strongly they affect the cell performance. The highest cell
efficiencies achieved with a silicon substrate were 7.2 percent AMO. One unexpected
problem was revealed in Phase I: diffusion from the silicon wafer into the p-type
buffer makes contact to the back of the cell difficult.
Potential Commercial Application:
Potential Commercial Application: The most likely application of this technology
would be power systems for satellites and spacecraft operating in orbits with the
highest radiation levels.