High efficiency multicrystalline silicon solar cells: Potential of n-type doping

By quantifying the role of dopants, impurities and crystal structure, we present guidelines for the fabrication of highly efficient multicrystalline (mc) silicon solar cells. Processed mc n-type wafers feature higher charge carrier diffusion lengths and thus a significantly larger efficiency potential compared with identically produced mc p-type wafers. Still, metal impurities limit the charge carrier lifetime in mc n-type wafers. We identify the main metal impurities in mc n-type silicon and quantify the resulting recombination losses. Attributing the main losses to precipitates and decorated crystal defects, the optimal efficiency potential of mc silicon is exploited by combining n-type high-performance multicrystalline silicon (HPM-Si) with a high efficiency cell concept featuring a full area passivated rear contact (TOPCon). The record cell features an efficiency of 19.6%, which is the highest efficiency reported for an mc n-type silicon solar cell. By reducing series resistance losses and improving the optics of the front surface, efficiencies of 21-22% should be attainable on n-type HPM-Si TOPCon solar cells.