SIMPLIFIED HIGH-EFFICIENCY SILICON CELL PROCESSING

We developed an emitter diffusion process that yields a near-ideal dop ing profile with a passivating oxide in a single furnace step. Because this process subjects the material to only one high-temperature therm al excursion, bulk lifetime is better preserved. This is especially tr ue for lower-cost silicon materials containing a high concentration of oxygen or carbon. Using this process, we routinely obtain one-sun cel l efficiencies over 19% on float-zone material and over 18% on Czochra lski material. Using solar-grade Czochralski material, we have demonst rated record efficiencies of 18.3% at one sun and 20.0% under concentr ation. Simple processes that yield high-performance diffusion profiles are expected to become increasingly important as manufacturers adopt improved techniques for ohmic contacts.