A novel technology for the simultaneous diffusion of boron, aluminum and phosphorus in silicon [solar cells]

A novel doping technique is presented to simultaneously diffuse boron, phosphorus and aluminum in Si solar cells in a single furnace step, without any detectable cross doping. This process also allows the growth of a passivating oxide in-situ, which is shown to be as good as a high quality re-grown thermal oxide. Three variations of this doping technique are presented to accommodate several solar cell designs, two of which involve the simultaneous diffusion of boron and phosphorus, while the third involves the simultaneous diffusion of aluminum and phosphorus in silicon. Initial results using boron and phosphorus gave a conversion efficiency of 19.3% on float zone silicon, 17.4% on Czochralski silicon, and 17.6% on multicrystalline silicon, while the aluminum and phosphorus process gave a conversion efficiency of 19% on float zone silicon.