Integration of subwavelength optical nanostructures for improved antireflection performance of mechanically flexible GaAs solar cells fabricated by epitaxial lift-off

Abstract

We demonstrate the integration of subwavelength moth-eye and Al 2 O 3 nanoisland structures fabricated on polymer packaging sheets and the surface of conventional Al 2 O 3 /TiO 2 bilayer antireflection coatings, respectively, with epitaxial lift-off singlejunction GaAs solar cells. The mechanically flexible cell structure with the integrated optical nanostructures shows substantially improved photovoltaic performance under various incident angles and bending radii compared to devices without such structures: the increase in short-circuit current density arising from integration of these nanostructures ranges from 9% at normal incidence to 52% at 80 o incidence; and the reduction in short-circuit current density under moderate bending decreases from 9.7% to 6.7%.

Increased performance of thin-film GaAs solar cells by rear contact/mirror patterning

“…Methods to remove the growth template wafer of GaAs solar cells, such as epitaxial lift-off (ELO), produce as final result thin-film devices that can be semitransparent or, more commonly, mounted on a metal foil that works as stable flexible handler and rear contact [1][2][3][4][5][6][7][8][9][10][11]. In the latter configuration, the rear contact also acts as mirror to the incident light, enabling cells to have even smaller thicknesses (of around 2 μm).…”