Type-II GaSb quantum dot solar cells were investigated for application to intermediate band solar cells. Multi-stacked GaSb quantum dots were embedded in the i-region of host GaAs or AlGaAs single-junction solar cells. Fourier transform photocurrent spectroscopy with absolute intensity calibration revealed infrared external quantum efficiency spectra by two-step photon absorption. Thermionic emission of photo-carriers was suppressed efficiently in these device architectures, and significant photocurrent production via two-step photon absorption was confirmed at room temperature operation.
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