Fabrication and analysis of thin-film GaAs solar cell on flexible thermoplastic substrate using a low-pressure cold-welding

We present flexible thin-film GaAs solar cells fabricated on thermoplastic substrates by a low-pressure cold-welding and epitaxial lift-off process. The use of polyethylene terephthalate (PET) film as a flexible substrate enables cold welding (130 °C) of gold layers between a thin-film GaAs solar cell and PET film with very low mechanical pressure (0.4 MPa), due to their thermoplastic properties. The feasibility of the proposed technique was demonstrated by fabricating GaAs single junction solar cells (without antireflection coating) on PET film, having an efficiency of 13.2%. The fabricated solar cell also showed a stable performance after 2000 cycles of bending.