Analysis of edge recombination for high-efficiency solar cells at low illumination densities

Indoor applications of high-efficiency silicon solar cells implicate illumination densities that are significantly below 1 sun. Our investigations show that at low illumination densities, solar cells are very sensitive to the recombination at the cell edges. We have analyzed the different recombination channels at the perimeter by means of two-dimensional device simulation and experiments. The modeling shows, that at low illumination densities the main recombination channel at the perimeter is due to the surface recombination in the space charge region. The surface recombination velocity at the cell perimeter could be extracted by comparison of the simulated and measured open-circuit voltages. Our investigation shows that the perimeter loss can be reduced drastically by an optimized passivation scheme.