Thin-film multiple-quantum-well solar cells fabricated by epitaxial lift-off process

Abstract

Thin-film solar cells fabricated using the epitaxial lift-off (ELO) process enable considerable cost reduction as well as light-trapping. A polyimide film was used as a support substrate for thin film devices to address the poor temperature tolerance of poly(ethylene terephthalate) films. Samples were stuck to polyimide films by an Au–Au bonding process. It was found that the insertion of a wetting layer enhanced the adhesion between a polyimide film and an Au layer. The achieved bonding was strong enough to carry out the ELO process, and no degradation was observed in cell performance. Thin-film solar cells with strain-balanced multiple quantum wells were also fabricated using the ELO process to benefit from the light-trapping effect. Quantum efficiency enhancement was observed in the long-wavelength range of 850–980 nm compared to the non-ELO-processed devices. The photo-absorption enhancement was due to the Fabry–Perot resonance between the surface and the rear Au electrodes.