High-power density (1040 W/kg) GaAs cells for ultralight aircraft

Ultralight 5 μm thick PIN GaAs solar cells were bonded to 3 mm coverglass with 1 mm of adhesive to create very high power density cells for use in ultralight aircraft. Cells were first made on a thick GaAs wafer and then bonded to a coverglass. The GaAs wafer was removed by selectively etching through the wafer to a buried etch stop in the cell epilayers. The cell was completed with a final nonalloyed back metal contact to prevent heat damage to the adhesive, as opposed to a high temperature alloyed contact used in a normal thick p-n GaAs cell. Prototype 1×1 cm cells were measured by microbalance at an average weight of 0.0228 g/cm² with a one-Sun AMO efficiency up to 17.3% at 28 °C (V_oc 1.024 V, J_sc 29.9 mA/cm ², fill factor 77.4%) for a solar cell power density of 1040 W/kg (weight including coverglass, adhesive and cell)