Effect of Front-Surface Doping onBack-Surface Passivation in GaInPand GaAs Cells

The emitter doping of a solar cell usually affects the blue response of the cell because the blue light is strongly absorbed at the front of the cell in the emitter layer. However, we show here that changing the identity of the dopant at the front of the cell affects the performance of the back of the cell, sometimes more than the performance of the front of the cell. Specifically, a highly Zn-doped Ga0.5In0.5P layer makes a good back-surface field in an n-on-p Ga0.5In0.5P cell with Se doping, but not when Si doping is used, consistent with the results of Takamoto, et al. During growth of the n-type layers, Zn diffuses up through the cell, piling up at the junction. When Si doping is used, the diffusion is enhanced.