Study on the effect of reverse current blocking layer for concentrator solar cells

In high concentration photovoltaic (HCPV) systems, III-V multijunction solar cells work under high concentration condition at a small size, normally less than 1cm². In this case, the metal coverage ratio and the current density become larger than those in the case of flat-plate solar cells. Due to the high current density, combined with the sheet resistance of solar cells, most of currents reverse to photocurrents flow vertically under front metal grids. This non-uniformity is critical when the metal coverage ratio is large as the case of concentrator solar cells. In this paper, the effects of metal coverage ratio and non-uniform reverse current density (i.e. forward bias current density) on the performance of InGaP/InGaAs/Ge triple-junction solar cells under high concentration were analyzed in detail. Moreover, by introducing reverse current blocking layer between metal busbar and AlInP window layer, we have successfully reduced the unwanted reverse current and achieved significant improvement in cell efficiency under high concentration condition.