Radiation-resilient ultra-thin GaAs solar cells on glass transferred by anodic bonding

Abstract

Ultra-thin GaAs photovoltaics with light management offer flexible form factors, higher specific power, a route to low material cost, and inherent resilience to damaging radiation environments in space, compared to conventional on-wafer architectures with thick absorbers. Here we demonstrated an adhesive-free method of bonding ultra-thin GaAs solar cells to borosilicate glass by anodic bonding. This off-wafer processing method replaces the III-V growth substrate with a glass superstrate offering higher specific power in addition to space radiation protection. In the glass-as-superstrate embodiment, the maximum power density (Pmax) remaining factor achieves 0.86 after 1 MeV electron exposure with a fluence of $3.6\times 10^{16}$ cm⁻², equivalent to $>$ 15 years in a geostationary orbit (GEO), exceeding that of current commercial triple-junction space solar cells. The short-circuit current density (Jsc) of the ultra-thin GaAs solar cells with only 80 nm thick absorbers could be boosted to 17.69 mA/cm² using higher bandgap III-V alloys as contact and bonding layers, with further improvement of integrating advanced light management approaches for higher power conversion efficiency.