Wide-bandgap epitaxial heterojunction windows for silicon solar cells

It is shown that the efficiency of a solar cell can be improved if minority carriers are confined by use of a wide-bandgap heterojunction window. For silicon (lattice constant a=5.43 AA), nearly lattice-matched wide-bandgap materials are ZnS (a=5.41 AA) and GaP (a=5.45 AA). Isotype n-n heterojunctions of both ZnS/Si and GaP/Si were grown on silicon n-p homojunction solar cells. Successful deposition processes used were metalorganic chemical vapor deposition (MO-CVD) for GaP and ZnS, and vacuum evaporation of ZnS. Planar