HIGH-EFFICIENCY THIN-FILM SILICON-ON-GAP SOLAR CELL FOR IMPROVED RADIATION RESISTANCE

THE ULTIMATE HIGH-EFFICIENCY CRYSTALLINE SILICON SOLAR CELL DESIGN CONSISTS OF A THIN FILM OF ELECTRICALLY-ACTIVE SILICON EPITAXIALLY GROWN ON AN OXIDE-OVERCOATED, INFRARED-TRANSPARENT GALLIUM PHOSPHIDE (GAP) SUBSTRATE. IN ADDITION TO HIGH CONVERSION EFFICIENCY AND INTRINSIC RADIATION RESISTANCE DUE TO THE THIN ACTIVE LAYERS, THIS NOVEL DESIGN HAS SEVERAL UNIQUE PERFORMANCE ENHANCING FEATURES. THE OXIDE OVERCOATING LAYER WILL SERVE AS A DIELECTRIC BACK SURFACE REFLECTOR TO ENHANCE THE OPTICAL ABSORPTION AND WILL ALSO ELIMINATE DANGLING BONDS IN THE EPITAXIALLY OVERGROWN SILICON LAYER, EFFECTIVELY PASSIVATING THE SILICON-OXIDE INTERFACE AND REDUCING BACK SURFACE RECOMBINATION. A HETEROJUNCTION CONTACT FORMED AT THE SILICONGAP INTERFACE THROUGH VIAS IN THE OXIDE WILL MINIMIZE BACK OHMIC CONTACT LOSSES. AND FINALLY, THE WIDE BANDGAP, INFRARED TRANSPARENT GAP SUBSTRATE WILL ALLOW LONG WAVELENGTH PHOTONS TO PASS THROUGH THE STRUCTURE WHICH WILL REDUCE THE OPERATING TEMPERATURE. IN ADDITION, SINCE THE ACTIVE DEVICE IS SILICON, DEVICE PROCESSING CAN TAKE ADVANTAGE OF STANDARD, SPACE-QUALIFIED, SILICON SOLAR CELL FABRICATION PROCEDURES. THE OBJECTIVE OF PHASE I IS TO DEMONSTRATE THE POTENTIAL OF THIS THIN-FILM SILICON SOLAR CELL STRUCTURE BY GROWING THIN EPITAXIAL LAYERS OF SILICON ON AN OXIDE-OVERCOATED GAP SUBSTRATE AND FABRICATING A SOLAR CELL THAT INCORPORATES THE IMPROVED FEATURES.