Title :
A simultaneously diffused, textured, in situ oxide AR-coated solar cell process (STAR process) for high-efficiency silicon solar cells
Author :
Krygowski, Thomas ; Rohatgi, Ajeet
Author_Institution :
Dept. of Electr. & Comput. Eng., Georgia Inst. of Technol., Atlanta, GA, USA
fDate :
1/1/1998 12:00:00 AM
Abstract :
A novel device fabrication process called the STAR process is presented, which incorporates a Simultaneously diffused emitter and Back Surface Field (BSF), on a textured silicon wafer, with an in situ thermal oxide for surface passivation and Anti-Reflection (AR) coating. In a single high-temperature step, the STAR process provides four important quality-enhancement features: (1) emitter oxide passivation, (2) back surface passivation via a boron back surface field, (3) a low reflectance (SiO2) single layer AR coating, and (4) a back surface reflector (BSR) for light trapping. The STAR process is implemented using a novel diffusion technique which can simultaneously form boron and phosphorus diffusions and grow an in situ thermal oxide in a conventional diffusion furnace, without the deleterious effects of cross doping. Conversion efficiencies as high as 20.1% have been obtained for this structure on 2.0 Ω·cm float zone silicon. This paper presents a detailed characterization of the impact of each of the above quality enhancement features, using a combination of an extended IQE analysis, minority carrier lifetime measurements, and measurements of the emitter saturation current density Joe. Computer simulations are used to improve the understanding of STAR cells and show that the STAR process is capable of producing device efficiencies over 19% on thin, relatively modest quality, solar grade silicon materials
Keywords :
antireflection coatings; carrier lifetime; diffusion; elemental semiconductors; minority carriers; passivation; silicon; solar cells; 20.1 percent; AR-coated solar cell process; B back surface field; STAR process; Si solar cells; Si-SiO2; Si:B-Si; anti-reflection coating; back surface field; back surface passivation; conversion efficiency; device fabrication process; diffusion technique; emitter oxide passivation; high-efficiency solar cells; in situ thermal oxide; light trapping; minority carrier lifetime measurements; quality-enhancement features; single high-temperature step; surface passivation; textured Si wafer; Boron; Coatings; Current measurement; Density measurement; Fabrication; Furnaces; Passivation; Reflectivity; Silicon; Surface texture;
Journal_Title :
Electron Devices, IEEE Transactions on