Voltage dependence of two-step photocurrent generation in quantum dot intermediate band solar cells

Elborg, Martin; Noda, Takeshi; Mano, Takaaki; Jo, Masafumi; Sakuma, Yoshiki; Sakoda, Kazuaki; Li, Han

doi:10.1016/j.solmat.2014.11.038

Cited by 23 publications

(16 citation statements)

References 23 publications

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“…Elborg et al . investigated the voltage dependence of extra photocurent for the GaAs/Al 0.28 Ga 0.72 As QD-IBSC23. In that literature, Δ J sc was 0.44 μA cm –2 when excited at the additional IR power density of 1,400 mW cm –2 .…”

Section: Discussionmentioning

confidence: 99%

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Two-step photon up-conversion solar cells

et al. 2017

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Reducing the transmission loss for below-gap photons is a straightforward way to break the limit of the energy-conversion efficiency of solar cells (SCs). The up-conversion of below-gap photons is very promising for generating additional photocurrent. Here we propose a two-step photon up-conversion SC with a hetero-interface comprising different bandgaps of Al0.3Ga0.7As and GaAs. The below-gap photons for Al0.3Ga0.7As excite GaAs and generate electrons at the hetero-interface. The accumulated electrons at the hetero-interface are pumped upwards into the Al0.3Ga0.7As barrier by below-gap photons for GaAs. Efficient two-step photon up-conversion is achieved by introducing InAs quantum dots at the hetero-interface. We observe not only a dramatic increase in the additional photocurrent, which exceeds the reported values by approximately two orders of magnitude, but also an increase in the photovoltage. These results suggest that the two-step photon up-conversion SC has a high potential for implementation in the next-generation high-efficiency SCs.

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Section: Discussionmentioning

confidence: 99%

“…According to ideal theoretical predictions, the IBSC is expected to exhibit extremely high conversion efficiency, >60%, under the maximum concentration and 48.2% under one-sun irradiation5. Substantial progress has been made in this field101112131415161718192021222324252627 since Luque and Martí have proposed this concept of IBSC in 1997 (ref. 5).…”

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confidence: 99%

Two-step photon up-conversion solar cells

et al. 2017

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“…This discussion is also applicable to sample C because both samples A and C have the type-II band alignment. We note that, since the photocurrent is generally given by the balance between the recombination and the thermal escape rates of holes in QDs, [23][24][25] the changes in the photocurrent and resultant I-V curves are not uniquely determined.…”

Section: Current-voltage Characteristicsmentioning

confidence: 97%

Dynamical properties and charge accumulation in solar cells with embedded GaSb quantum dots

Noda¹,

Elborg²,

Mano³

et al. 2018

Jpn. J. Appl. Phys.

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We studied the dynamical properties of quantum dot solar cells in which GaSb quantum dots (QDs) were embedded in the middle part of an undoped layer sandwiched by n-and p-layers. Three kinds of GaSb QDs with GaAs or AlGaAs as a barrier material for QDs were prepared for comparison of their properties. The capacitance C was measured as a function of the frequency f in the ranges between 5 kHz and 3 MHz under different illumination conditions. A rise in capacitance in response to illumination was observed in all the samples, showing that photogenerated carriers (or holes) contribute to the dynamical properties of solar cell devices. Differences in capacitance change among the three samples are observed in magnitude and its frequency dependence. We discuss them in terms of the difference in dynamical processes, specifically the thermal escape rate of holes in QDs.

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“…16 Elborg et al experimentally revealed that a maximum in TSPA occurred at a reverse bias of À0.3 V in GaAs/AlGaAs QDSCs. 17 Creti et al demonstrated that the effect of electric field on electron-hole separation along the growth direction can be used to preserve TSPA up to room temperature. 10 Kasamatsu et al has shown that a strong internal electric field of 193 kV/cm severely reduces the radiative lifetime of the ground state (GS) carriers thereby quenching TSPA, but internal electric fields on the order of 10 kV/cm still maintain QD electronic coupling.…”

Section: Introductionmentioning

confidence: 99%

Effect of electric field on carrier escape mechanisms in quantum dot intermediate band solar cells

Polly

Hellstroem

Slocum

et al. 2017

Journal of Applied Physics

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Carrier escape and recombination from quantum dot (QD) states reduce the probability of two-step photon absorption (TSPA) by decreasing the available carrier population in the intermediate band (IB). In order to optimize the second photon absorption for future designs of quantum dot embedded intermediate band solar cells, the presented study combined the results of simulations and experiments to quantify the effect of electric field on the barrier height and the carrier escape from the QDs in InAs/GaAs quantum dot solar cells with five-layer QD superlattices. The electric field dependent effective barrier heights for ground state electrons were calculated using eight band kÁp theory at short circuit conditions. With an increase in electric field surrounding the QDs from 5 kV/cm to 50 kV/cm, the effective barrier height of the ground state electrons was reduced from 147 meV to 136 meV, respectively. Thus, the increasing electric field not only exponentially enhances the ground state electron tunneling rate (effectively zero at 5 kV/cm and 7.9 Â 10 6 s À1 at 50 kV/cm) but also doubles the thermal escape rate (2.2 Â 10 11 s À1 at 5 kV/cm and 4.1 Â 10 11 s À1 at 50 kV/cm). Temperature-dependent external quantum efficiency measurements were performed to verify that the increasing electric field decreases the effective barrier height. Additionally, the electric field dependent radiative lifetimes of the ground state were characterized with time-resolved photoluminescence experiments. This study showed that the increasing electric field extended the radiative recombination lifetime in the ground state of the QDs as a consequence of the reduced wave-function overlap between the electrons and holes. The balance of carrier escape and recombination determines the probability of TSPA. Published by AIP Publishing.

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Voltage dependence of two-step photocurrent generation in quantum dot intermediate band solar cells

Cited by 23 publications

References 23 publications

Two-step photon up-conversion solar cells

Two-step photon up-conversion solar cells

Dynamical properties and charge accumulation in solar cells with embedded GaSb quantum dots

Effect of electric field on carrier escape mechanisms in quantum dot intermediate band solar cells

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