An Infant Mortality Study of III-V Multijunction Concentrator Cells

Six hundred and forty III-V triple-junction solar cells were evaluated in this study. The cells were initially electrically and optically characterized prior to being packaged and placed on-sun for a short exposure. Following exposure, the cells were partitioned according to their performance change. An infant mortality rate of 0.5% was observed and attributed to preexisting voids in the die attach that promoted thermal runaway. All other cells that significantly degraded following exposure were initially measured with shunt currents >mA at 1.5 V; therefore, a similar limit would serve as an appropriate screening current and only reduce yield by ∼ 1.5%. While many cells both above and below this shunt current limit exhibited artifacts in their electroluminescence (EL) emission, it was not found to predict subsequent performance. The current investigation, however, focused on detecting a short-term degradation and did not evaluate how artifacts in the EL emission or a short-term change in shunt current may correlate with other wear out mechanisms.