ORCID Profile
0000-0002-1547-5477
Current Organisation
University of Tokyo
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Publisher: AIP Publishing
Date: 22-04-2013
DOI: 10.1063/1.4803459
Abstract: We report the effects of the deposition of an AlAs cap layer (CL) over InAs quantum dots (QDs) on the performance of QD solar cells (QDSCs). The growth of AlAs CL over InAs QDs led to the elimination of the wetting layer absorption and hence the enhancement of the open-current voltage, Voc, of a 20-layer InAs/GaAs QDSC from 0.69 V to 0.79 V. Despite a slight reduction in short-circuit current, Jsc, for the QDSC with AlAs CL, the enhancement of the Voc is enough to ensure that its efficiency is higher than the QDSC without AlAs CL.
Publisher: AIP Publishing
Date: 06-2015
DOI: 10.1063/1.4916561
Publisher: Springer Science and Business Media LLC
Date: 03-2021
DOI: 10.1038/S42005-021-00543-1
Abstract: A detailed balance calculation reveals an extremely high efficiency of 63.2% for intermediate-band solar cells (IBSCs) under maximum sunlight concentration. However, an actual IBSC device with an efficiency larger than the Shockley-Queisser (SQ) limit has so far not been reported. The main difficulties lie in realizing an efficient sequential two-photon absorption (STPA) which requires a sufficiently long lifetime intermediate state or intermediate band. In this article, we propose the concept of a ratchet type IBSC, utilizing a long lifetime of rare-earth ion luminescence centers in Erbium-doped GaAs. The temperature dependent differential external quantum efficiency reveals a significant STPA contribution originating from the Er 3+ luminescence center. All the results were modeled and interpreted by integrating the ratchet effect with up-conversion along with a density functional theory (DFT) simulation. Our work demonstrates that the long lifetime energy-transfer mechanism in Er 3+ centers contributes directly to the formation of a ratchet type IB.
Publisher: IEEE
Date: 06-2011
Publisher: Wiley
Date: 20-01-2015
DOI: 10.1002/PIP.2585
Publisher: IOP Publishing
Date: 24-06-2016
Publisher: Elsevier BV
Date: 03-2014
No related grants have been discovered for Yoshitaka Okada.