VERY LOW-COST/HIGH-EFFICIENCY THIN-FILM SILICON PHOTOVOLTAIC TECHNOLOGY

THE GOAL OF THIS PROJECT IS TO ACHIEVE A COST REDUCTION ON THE ORDER OF 50% IN THIN-FILM PHOTOVOLTAIC (PV) TECHNOLOGY BY DEVELOPING A HIGH-EFFICIENCY CHEMICAL VAPOR DEPOSITION (CVD) SILICON CELL UTILIZING A LOW-COST SUBSTRATE. IN PHASE I A SURFACE RELIEF STRUCTURE WILL BE FORMED ON A GLASS SUBSTRATE BY MAKING A NEGATIVE REPLICA OF A REUSABLE TEXTURE-ETCHED SILICON SURFACE. A THIN SILICON FILM WILL BE DEPOSITED ON THIS TEXTURED SUBSTRATE BY CVD FROM SILANE AND THEN RECRYSTALLIZED BY RAPID THERMAL ANNEALING. THE ARTIFICIAL SURFACE RELIEF WILL INDUCE A PREFERRED ORIENTATION OF THE REGROWN CRYSTALLITES (GRAPHOEPITAXY) SO THAT THE FILM HAS A NEARLY SINGLE CRYSTAL, OR AT LEAST LARGED-GRAINED ( 1 MM), STRUCTURE. IN PHASE II, A CELL STRUCTURE WITH ALL CONTACTS ON THE BACK SURFACE WILL BE FABRICATED, THE TEXTURED GLASS SUBSTRATE BECOMING THE LIGHT-TRAPPING FRONT COVER OF THE CELL. ALTHOUGH HIGHLY INNOVATIVE, THIS APPROACH IS AT AN ACCEPTABLY LOW LEVEL OF RISK BECAUSE IT IS BASED UPON THE SYNTHESIS OF FIVE PREVIOUSLY DEMONSTRATED TECHNOLOGIES: GRAPHOEPITAXY, SCANNED RECRYSTALLIZATION, INTERDIGITATED BACK CONTACT CELL STRUCTURES, LIGHT TRAPPING, AND HIGH LIFETIME CVD SILICON.