Modelling of the perimeter recombination effect in GaAs-based micro-solar cell

Results obtained using one-dimensional simulator SCAPS–1D are modified to account for perimeter recombination which is a two-dimensional effect. The modification consists mainly of adding a perimeter contribution to the dark current of the cell. The perimeter recombination current in micro-solar cells is analysed on the basis of a model in which the Fermi level pinning reduces the electric field at the surface of the space-charge region. Consequently, the surface recombination effective width is increased. A simple analytical form of the perimeter current at the space-charge region surface is developed, surface recombination outside this region is neglected. The obtained results agree well with reported experimental results of a 0.5cm×0.5cm GaAs solar cell. The calculation demonstrates that perimeter current affects seriously the performance of small area solar cells. For solar cells with a perimeter to area ratio (P/A) greater than 100 cm−1 the expected bulk recombination current is two to three orders of magnitude too small to account for. The performance of small area solar cells are reduced by the perimeter effect, the most important deterioration is recorded in the theoretical energy conversion efficiency ηη.