Strain-free ring-shaped nanostructures by droplet epitaxy for photovoltaic application.

Droplet epitaxy is a flexible nanomaterial growth technique and is a potential method to fabricate advanced electronic and optoelectronic devices. Here, we report strain-free GaAs/Al0.33Ga0.67As quantum ring solar cells fabricated by droplet epitaxy technique. Photoluminescence is used to study the electronic structure of the lattice-matched GaAs/Al0.33Ga0.67As quantum ring solar cells. Post-growth thermal annealing is used to improve the optical quality of the solar cell as well as device efficiency. A power conversion efficiency of 1.8% is demonstrated from a prototype quantum ring solar cell. This work opens new opportunities for quantum dot solar cells with strain-free nanostructures. [ABSTRACT FROM AUTHOR]