Study of the Causes of Degradation of Space III-V Multijunction Solar Cells at Reverse Bias Operation

Reverse biasing triple-junction GaInP/Ga(In)As/Ge solar cells may affect their performance by the formation of permanent shunts. In a previous work, it was observed that, amid the three components, GaInP subcells are more prone to degradation when reverse biased suffering permanent damage even at low reverse bias voltages. The aim of this work is to find out what is causing the catastrophic failure of the solar cells and whether the initial characteristics of the devices –as their dark I-V curves– can help to anticipate if the device will degrade at low reverse voltages. For this, electroluminescence and reverse dark I-V curve measurements, as well as Nomarsky microscope analysis have been carried out. With these measurements, some conclusions can be drawn: the defect that causes the final failure is always beneath a metallized region, so visual inspection could be used to discard potentially problematic devices.