Design criteria for Si point-contact concentrator solar cells

Design criteria for concentrator solar cells are presented for the highly three-dimensional case of backside point-contact solar cells. A recent new experimental result, a 28-percent efficient cell (25°C, 15-W/cm²incident power) is used as a case study of the dependences of the recombination components and the carrier density gradients on the geometrical design parameters. The optimum geometry is found to depend upon the intended design power density as well as the attainable physical parameters allowed by the fabrication techniques utilized. Modeling projections indicate that an ultimate efficiency of 30.6 percent (36 W/cm², 300 K) is achievable using the diffused emitters presently employed on these cells. Incorporation of results from the study of polycrystalline emitters could improve these efficiencies toward 31.7 percent.