MONOLITHIC INTEGRATION OF THIN FRILM PHOTOVOLTAICS ON INSULATED METAL SUBSTRATES

THIN FILM SEMICONDUCTORS OFFER THE BEST OPPORTUNITY FOR COST REDUCTION OF PHOTOVOLTAICS. GLASS IS COMMONLY USED AS A SUBSTRATE, BUT BREAKAGE REMAINS A PROBLEM. THIS PHASE I PROJECT WILL DEMONSTRATE THE TECHNICAL FEASIBILITY OF PREPARING MONOLITHICALLY INTEGRATED, THIN FILM PHOTOVOLTAIC (PV) CELLS ON INSULATED METAL SUBSTRATES. THE KEY REQUIREMENT IS DEVELOPMENT OF A LOW COST METAL/INSULATOR COMBINATION THAT IS COMPATIBLE WITH THE PB TECHNOLOGY. THE INSULATING LAYER MUST EXHIBIT GOOD ADHESION AND BE FREE OF PINHOLES. ANODIZED ALUMINUM SHEET AND GLASS-COATED (PORCELAINIZED) STEEL HAVE BEEN IDENTIFIED AS PROMISING CHOICES. INSULATED SUBSTRATES WILL BE PREPARED BY LOW TEMPERATURE ANODIZATION OF ALUMINUM (A1) UNDER APPROPRIATE CONDITIONS TO FORM THICK OXIDES (WHICH WILL THEN BE SEALED), AND BY FORMULATION OF ALKALI ALUMINOBOROSILICATE GLASS FRITS FOLLOWED BY BONDING TO LOW CARBON STEEL SHEET AT 850 DEGREES CENTIGRADE. THE COATINGS WILL BE TESTED FOR ADEQUATE DIELECTRIC PROPERTIES, BREAKDOWN VOLTAGE IN EXCESS OF 1500 V, AND ION MOTION. ALKALI-FREE FRITS WILL ALSO BE EVALUATED. THIN FILM, MONOLITHICALLY INTERCONNECTED STRUCTURES WILL BE FABRICATED IN THE CONFIGURATIONS COPPER INDIUM SELENIDE (CIS) ON PORCELAINIZED STEEL AND AMORPHOUS SILICON ON ANODIZED A1. DURING CIS FORMATION, THE SUBSTRATE WILL BE EXPOSED TO SELENIUM AND TO TEMPERATURES UP TO 550 DEGREES CENTIGRADE. THE RESULTING DEVICES WILL BE ANALYZED BY A VARIETY OF TECHNIQUES FOR INTEGRITY OF THE INSULATOR, ADHESION, IMPURITIES, DELETERIOUS CHEMICAL REACTIONS, AND SOLAR CONVERSION EFFICIENCY. THE ABOVE OPERATIONS WILL BE ITERATED AND OPTIMIZED WITH THE GOAL OF FORMING WORKING PROTYTYPE DEVICES.