Efficiency Improvement by Deeper Emitter with Lower Sheet Resistance for Uniform Emitters

By reducing the peak concentration of phosphorus doping and raising the sheet resistance of a uniform emitter from 66 to 76 ohm/square, a 0.2%abs efficiency gain was achieved for multicrystalline silicon solar cells. No extra process time or step is needed to obtain this improved efficiency. Increasing the sheet resistance and reducing the peak concentration narrows the process window. Manipulation of the doping profile towards a deeper emitter with lower peak concentration does not have these drawbacks. The resulting process leads to a 0.3%abs efficiency gain at a lower sheet resistance (51-56 ohm/square). A wide process window with a large tolerance for metal contacting is obtained. By statistical analysis and PC1D simulations, the legitimacy of the positive contribution of the deeper emitter is shown.