Co-optimisation of the emitter region and the metal grid of silicon solar cells

The procedure for the simultaneous optimisation of the dopant density profile and the front metal grid of silicon solar cells is illustrated with representative cases of laboratory and commercial devices. Contour plots for the saturation current density and the photo-generated current density of phosphorus doped emitter regions of silicon solar cells are calculated as a function of emitter thickness and dopant concentration, for the particular case of Gaussian dopant profiles. To expose the competing factors of surface and bulk emitter recombination, grid shading and series resistance, the other regions of the device are assumed ideal, that is, loss-less. The calculated contour plots of the conversion efficiency indicate that relatively thick emitters are optimum if surface passivation is available, whereas thin, heavily doped emitters are preferable in the absence of surface passivation.