Solar Cell Performance after Exfoliation Using Sonic Liftoff

Removing grown device layers from a GaAs substrate is an essential aspect of reducing costs of III-V photovoltaics. While many methods of device layer removal have been explored, Sonic Lift-off (SLO) demonstrates novel control of the stress conditions within the substrate during exfoliation. By utilizing acoustic energy, this technique allows for a lower maximum stress required to fully lift-off layers from a substrate. We demonstrate that this technique results in no damage to inverted-grown and upright-grown exfoliated devices. The inverted device demonstrated an efficiency of 26.8% after SLO in comparison to 26.5% for a traditionally-processed cell, and the upright device showed a 22.0% efficiency after SLO. The SLO process has been shown to produce exfoliated, damage-free devices and opens the door for substrate reuse to reduce the cost of III-V photovoltaics.