Tunnel Diode Revealing Peculiarities at I-V Measurements in Multijunction III-V Solar Cells

This work reports on various approaches to illuminated I-V curve measurements in monolithic dual and triple-junction GaInP/GaAs/Ge cells with the aim of revealing the action of interconnecting tunnel diodes. The measurements were performed both for model samples using a combination of individual sub-cells, connected through an external tunnel diode and for practical concentrator cells with different peak current densities (J_p) of the tunnel diodes in a monolithic structure. Changing of load resistance, or changing of applied voltage from an external source, characterized by variable resistance, was used to obtain I-V curves under both continuous and flash illumination. Also, variation of cell internal resistance due to the current mismatch in sub-cells, caused by illumination spectrum variation, was proven by these measurements