A good recipe to make silicon solar cells

A fabrication process that is simple, uses conventional equipment, and yet is capable of producing high efficiency crystalline silicon solar cells is described. It is based on a deep phosphorus diffusion to form the front emitter region and a deep aluminum diffusion to form a back BSF region. The total charge of phosphorus atoms is controlled to the desired level in a conventional open-tube POCl₃ furnace by adjusting the mix of gases that flow into it, the time and the temperature. A thin SiO₂ layer is grown in the same diffusion tube to passivate the surface. After aluminum deposition on the back side, the wafers go directly to a second furnace where both dopants are driven in for a relatively long time at a high temperature. One of the best features of this process is that it minimizes wet etching and cleaning steps. The resulting devices have a relatively thick, moderately doped and surface-passivated emitter well suited for low-cost metallization techniques