An optimization study of Si point-contact concentrator solar cells

A three-dimensional model developed for Si point-contact solar cells is applied to analyze data from a wide range of device geometries in order to study the effects on device performance. These modeling simulations make use of measured parameters for the surface recombination velocities, bulk lifetimes, and emitter saturation currents as well as recent measurements of the Auger recombination. A 28-percent-efficient cell (15 W/sq cm, 25 C) provides data for 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 on the intended design power density as well as the attainable physical parameters for the fabrication sequence utilized. Modeling projections indicate that an ultimate efficiency of 30.6 precent (36 W/sq cm, 300 K) may be achieved with the diffused emitters currently used in these cells. Incorporation of results from the study of polycrystalline emitters could raise these efficiencies as high as 31.7 percent.