Heterointerfaces in MJ SC: IV curves and their peculiarities

The heterointerface IV curves at different intensity illumination levels have been extracted from full IV curves of triple-junction GaInP/GaAs/Ge solar cell. For this purpose a special approach for multi-junction solar cells has been proposed. The solar cell equivalent circuit consisting of two parts – generation and connecting ones were considered. The generation part includes all photovoltaic p-n junctions, while connecting one incudes a resistance of the layers, spreading resistance, tunnel diodes and heterointerfaces. The equivalent circuit was used for analysis of «kink» free IV curves of Ge and GaAs solar cells. In this case the IV curves of connecting part are completely described by the spreading resistance. The analysis of GaInP/GaAs/Ge allows to obtain heterointerface IV curves and it has been shown that their shape depends on illumination level. The empirical formula was used for an approximation of heterointerface IV curves to show the nature of current flow mechanism which was established as tunneling one.