Bend Testing of IMM and Triple Junction Solar Cells

A number of SolAero Inverted Metamorphic Multijunction (IMM) and ZTJ solar cells, both bare and CICs, were subjected to ever increasing displacement 4-point bend testing. Following each flexure, the cells were characterized by current-voltage and electroluminescence measurements. The data demonstrated that on average IMM CICs can be displaced 65% further than ZTJ CICs before fracturing. The IMM CICs are also more easily flexed, bending $∼65$% further under equivalent load. Finally, the electrical degradation behavior were very different for the IMM and ZTJ devices, with the ZTJ demonstrating a step-like loss in performance when fractured whereas the IMM demonstrated a more graceful degradation. Modifications to the IMM configuration may be beneficial in significantly reducing the degradation, providing an even larger mechanical benefit.