Characteristics of highly stacked quantum dot solar cells fabricated by intermittent deposition of InGaAs

We report GaAs-based quantum dot (QD) solar cells fabricated by the intermittent deposition of InGaAs using molecular beam epitaxy. We obtained a highly stacked and well-aligned InGaAs/GaAs QD structure of over 100 layers without using a strain compensation technique. The external quantum efficiency of multistacked InGaAs QD solar cells extends the photo-absorption spectra toward a wavelength longer than the GaAs band gap, and the efficiency increases as the number of stacking layers increases. The short-circuit current density of the solar cells increases as the number of InGaAs QD layers increases. Moreover, InGaAs QD solar cells have high open circuit voltage and good cell characteristics even though an interdot spacing is reduced to 3.5 nm. The performance of the QD solar cells indicates that the novel InGaAs QDs facilitate the fabrication of highly stacked QD layers that are suitable for solar cell devices requiring thick QD layers with a minband for sufficient light absorption.