Low-temperature fabrication technologies of Si solar cell by sputter epitaxy method

We applied an epitaxial n+-type Si emitter layer grown on a p-type Si substrate by our environmentally-light-load sputter epitaxy method using RF magnetron sputtering without dopant activation annealing for a Si solar cell. We also applied low-temperature cleaning of the substrate with a hydrogen-fluoride treatment at room temperature prior to the emitter layer growth instead of the conventionally used high-temperature thermal cleaning under vacuum condition. In addition, by our sputter epitaxy method, we determined the optimum temperature for the emitter growth. An emitter layer with good crystallinity is obtained, and the solar cell, formed with an emitter layer grown at the optimum growth temperature of 410 °C, exhibits an energy conversion efficiency of 12.3% in 100% aperture ratio equivalent without a texture or an antireflection coat. By the above low-temperature processes, a solar cell can be fabricated with process temperatures below 410 °C, which exhibits low temperature processes.