Evidence of two-photon absorption in strain-free quantum dot GaAs/AlGaAs solar cells

We report the fabrication procedure and the characterization of an Al0.3Ga0.7As solar cell containing high‐density GaAs strain‐free quantum dots grown by droplet epitaxy. The production of photocurrent when two sub‐bandgap energy photons are absorbed simultaneously is demonstrated. The high quality of the quantum dot/barrier pair, allowed by the high quality of nanostructured strain‐free materials, opens new opportunities for quantum dot based solar cells. Left: Scheme of the fabricated quantum dot solar cell. Right: 1 × 1 µm2 image of the dot layer. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) An intermediate band solar cell containing high‐density, strain‐free quantum dots grown by droplet epitaxy is demonstrated to produce photocurrent when two sub‐bandgap energy photons are absorbed simultaneously. The quality of the quantum dot/barrier pair – allowed by the absence of strain‐related defects, the good confinement, and the capability of droplet epitaxy to grow high‐density and large aspect ratio quantum dots – opens new opportunities for quantum dot based solar cells.