The effect of emitter profile on laser doped multicrystalline silicon selective emitter cells

The emitter dopant profile between the metal grid in lase doping selective emitter cells was modified by oxidation the phosphosilicate glass (PSG) film at a higher temperature. This diffusion process contains two steps. Step 1 form the PSG layer on the wafer surface by the reaction of POCl3 and oxygen. Step 2 increase the temperature to a higher value at which the oxidation of PSG layer is proceeded. For the practical cell process, the laser power and front metal-grid were optimized, considering the dependence on the light induced plating nickel-silicon contact and on the emitter sheet resistance. Comparing with the uniform emitter multicrystalline silicon solar cells, significant increase of short circuit current by 0.3 A and open circuit voltage by 6 mV was obtained resulting in an average gain of 0.6%abs. An average efficiency of 17.2% and the largest of 17.42% for the best cell on a large area commercial grade p-type multi-crystalline silicon substrate were achieved.