A simple single photomask process for fabrication of high-efficiency multicrystalline-silicon solar cells

The authors have developed a simplified process sequence for the fabrication of high-efficiency multicrystalline-silicon (mc-Si) solar cells. Photolithography is required only to define the evaporated metal gridlines. The authors use this fast turn-around, high-yield baseline process to evaluate different mc-Si materials and new processing procedures. The process uses a one-step emitter diffusion/drive-in and an aluminum-alloyed back surface field to provide a well-passivated cell with excellent blue and red response. Laser-scribed cell-isolation grooves are used to define both moderate-area (4, 4.6, or 10.5 cm² ) and large-area (42 cm²) cells. They have observed minority carrier diffusion lengths of around 300 μm in 1.4-Ωcm mc-Si material and have achieved efficiencies of 16.8% in 4.6-cm² cells. Large-area cell efficiencies in the same material have reached 16.4%