Progress on Substrate Reuse Using Sonic Lift-Off for GaAs- Based Photovoltaics

Abstract

Sonic lift-off is able to reduce average surface facet amplitude without degrading bulk material quality and is thus a promising technology for enabling repeated substrate reuse with GaAs-based photovoltaics. J-sun AM1.5G illuminated current density-voltage data and spectral response data from four devices at different stages of the spalling process have been presented. Devices grown on a commercial substrate and then acoustically-spalled as well as devices grown on a previously acoustically-spalled substrate with minimal surface treatment did not show degradation in device performance compared to the control grown on a commercial substrate, which was 17% efficient without anti-reflection coatings. Devices grown on a previously acoustically-spalled substrate and then spalled exhibited degradation in both short-circuit current density and open circuit voltage for a final 8% efficiency, indicating further process improvements are necessary to realize efficient substrate reuse.