Fabrication of InAs/GaAs quantum dot solar cells with enhanced photocurrent and without degradation of open circuit voltage

Guimard, Denis; Morihara, Ryo; Bordel, D.; Tanabe, Katsuaki; Wakayama, Yuki; Nishioka, M.; Arakawa, Yasuhiko

doi:10.1063/1.3427392

Cited by 230 publications

(156 citation statements)

References 20 publications

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“…QDs of the desired size (down to 2-3 nm) have been produced through this technique 50 and can be implemented with several material options that give a bandgap distribution close to the optimum value of 1.95 eV, with good lattice matching. Nevertheless, some carefully manufactured InAs/GaAs cells have already presented minor voltage reductions 18,19 and are therefore probably already operating as IB cells at room temperature.…”

Section: Summary and Challengesmentioning

confidence: 99%

Understanding intermediate-band solar cells

2012

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The intermediate-band solar cell is designed to provide a large photogenerated current while maintaining a high output voltage. To make this possible, these cells incorporate an energy band that is partially filled with electrons within the forbidden bandgap of a semiconductor. Photons with insufficient energy to pump electrons from the valence band to the conduction band can use this intermediate band as a stepping stone to generate an electron-hole pair. Nanostructured materials and certain alloys have been employed in the practical implementation of intermediate-band solar cells, although challenges still remain for realizing practical devices. Here we offer our present understanding of intermediate-band solar cells, as well as a review of the different approaches pursed for their practical implementation. We also discuss how best to resolve the remaining technical issues.T he intermediate-band (IB) solar cell consists of an IB material sandwiched between two ordinary n-and p-type semiconductors 1 , which act as selective contacts to the conduction band (CB) and valence band (VB), respectively (Fig. la). In an IB material, sub-bandgap energy photons are absorbed through transitions from the VB to the IB and from the IB to the CB, which together add up to the current of conventional photons absorbed through the VB-CB transition. In 1997 2 , researchers used hypotheses similar to those adopted by Shockley and Queisser in 1961 3 to derive a detailed balance-limiting efficiency of 63% for the IB solar cell, at isotropic sunlight illumination (concentration of 46,050 suns) and assuming Sun and Earth temperatures to be 6,000 K and 300 K, respectively (Fig. lb). This work also presented the Shockley-Queisser limiting efficiency of 41% for single-gap solar cells operating under the same conditions 2 . The limiting efficiency of the IB solar cell is similar to that of a triple-junction solar cell connected in series. However, the IB can be regarded 4 as a set of two cells connected in series (corresponding to the VB-IB and IB-CB transitions) and one in parallel (corresponding to the VB-CB transition). This provides the IB solar cell with additional tolerance to changes in the solar spectrum.An optimal IB solar cellhas a total bandgap of about 1.95 eV, which is split by the IB into two sub-bandgaps of approximately 0.71 eV and 1.24 eV The quasi-Fermi levels (QFLs) or electrochemical potentials of the electrons in the different bands are usually close to the edges of the bands. Because the voltage of any solar cell is the difference between the CB QFL at the electrode in contact with the n-type side and the VB QFL at the electrode in contact with the p-type side, the maximum photovoltage of the IB solar cell is limited to 1.95 eV, although it is still capable of absorbing photons of energy above 0.71 eV In contrast, single-gap solar cells cannot supply a voltage greater than the lowest photon energy they can absorb. IB solar cells can deliver a high photovoltage by absorbing two subbandgap photons to produce one high ...

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Section: Summary and Challengesmentioning

confidence: 99%

Understanding intermediate-band solar cells

2012

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“…The absorption of sub-bandgap photons and the possibility of minimal degradation of the open circuit voltage in comparison with single junction GaAs solar cells have been reported. [15][16][17] The absorption energies for the InAs/GaAs system are, in principle,…”

Section: A Theoretical Modelmentioning

confidence: 99%

InAs quantum dot growth on AlxGa1−xAs by metalorganic vapor phase epitaxy for intermediate band solar cells

Jakomin

Kawabata

Mourão

et al. 2014

Journal of Applied Physics

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“…1. Several groups have manufactured QDIBSCs following this approach [5][6][7][8][9] and experimentally demonstrated some of the principles of IBSC operation, such as the production of electron-hole pairs by below-bandgap energy photons 10 or the existence of quasi-Fermi level separation between the CB and IB. 11 However, the experimental work carried out so far has also allowed identifying the factors that prevent boosting the efficiency of realistic QDIBSCs above that of single gap solar cells.…”

Section: On Inhibiting Auger Intraband Relaxation In Inas/gaas Quantumentioning

confidence: 99%

On inhibiting Auger intraband relaxation in InAs/GaAs quantum dot intermediate band solar cells

Tomić

Martı́

Antolín

et al. 2011

Applied Physics Letters

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The operation of ideal quantum dot intermediate band solar cell requires the largest possible reduction of carrier relaxation from the conduction band to the intermediate band (intraband relaxation) so that it approaches the radiative limit. In this respect, we examine the contribution to this relaxation of Auger related electron cooling non-radiative mechanisms and suggest ways of suppressing them.

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Fabrication of InAs/GaAs quantum dot solar cells with enhanced photocurrent and without degradation of open circuit voltage

Cited by 230 publications

References 20 publications

Understanding intermediate-band solar cells

Understanding intermediate-band solar cells

InAs quantum dot growth on AlxGa1−xAs by metalorganic vapor phase epitaxy for intermediate band solar cells

On inhibiting Auger intraband relaxation in InAs/GaAs quantum dot intermediate band solar cells

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