Improvement of multicrystalline silicon solar cells by a low temperature anneal after emitter diffusion

The influence of an annealing step at about 500°C after emitter diffusion of multicrystalline solar cells is investigated. Neighboring wafers from a silicon ingot were processed using different annealing durations and temperatures. The efficiency of the cells was measured and detailed light beam induced current measurements were performed. These show that mainly areas with high contents of precipitates near the crucible walls are affected by the anneal. An efficiency increase from 14.5 to 15.4% by a 2h anneal at 500°C was observed. The effect seems to be more likely external than internal gettering.