Voltage limitation analysis in strain-balanced InAs/GaAsN quantum dot solar cells applied to the intermediate band concept

Linares, P.G.; López, E.; Ramiro, I.; Datas, Alejandro; Antolín, E.; Yoshida, Shoji; Sogabe, Tomah; Okada, Yoshitaka; Martı́, Antonio; Ĺuque, A.

doi:10.1016/j.solmat.2014.08.041

Cited by 23 publications

(12 citation statements)

References 25 publications

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“…While this has been demonstrated to be effective, the influence of these low bandgap (compared to the spacers) barriers on the V OC has not been discussed. Low bandgap barriers may lead to a fundamental reduction of the limiting V OC (from E G to the bandgap of the barriers, E B ) [31]. This is why we have decided to use AlGaAs barriers, where E B (1.84 eV) is close to E G (1.88 eV), in order to achieve a good bandgap distribution but avoiding the possibility imposing a lower limit to the V OC .…”

Section: Discussionmentioning

confidence: 99%

Wide-Bandgap InAs/InGaP Quantum-Dot Intermediate Band Solar Cells

Ramiro

Villa

Lam

et al. 2015

IEEE J. Photovoltaics

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Abstract-Current prototypes of quantum-dot intermediate band solar cells suffer from voltage reduction due to the existence of carrier thermal escape. An enlarged sub-bandgap E L would not only minimize this problem, but would also lead to a bandgap distribution that exploits more efficiently the solar spectrum. In this work we demonstrate InAs/InGaP QD-IBSC prototypes with the following bandgap distribution: E G = 1.88 eV, E H = 1.26 eV and E L > 0.4 eV. We have measured, for the first time in this material, both the interband and intraband transitions by means of photocurrent experiments. The activation energy of the carrier thermal escape in our devices has also been measured. It is found that its value, compared to InAs/GaAs-based prototypes, does not follow the increase in E L . The benefits of using thin AlGaAs barriers before and after the quantum-dot layers are analyzed.

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Section: Discussionmentioning

confidence: 99%

Wide-Bandgap InAs/InGaP Quantum-Dot Intermediate Band Solar Cells

Ramiro

Villa

Lam

et al. 2015

IEEE J. Photovoltaics

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“…The 8e − ∕QD doping resulted in the highest V oc of 0.932 V, which can be considered a direct effect from the decreased SRH recombination due to the shift of intrinsic region. 29,40 However, the doping-induced band flattening has weakened the carrier collection due to the decreased electric field in the QD region. This negative effect was directly linked to the reduction of J sc for all doped samples.…”

Section: Doping Effect On Inas/gaas Quantum Dot Solar Cell Performancementioning

confidence: 99%

Recent progress on quantum dot solar cells: a review

2016

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Abstract. Semiconductor quantum dots (QDs) have a potential to increase the power conversion efficiency in photovoltaic operation because of the enhancement of photoexcitation. Recent advances in self-assembled QD solar cells (QDSCs) and colloidal QDSCs are reviewed, with a focus on understanding carrier dynamics. For intermediate-band solar cells using selfassembled QDs, suppression of a reduction of open circuit voltage presents challenges for further efficiency improvement. This reduction mechanism is discussed based on recent reports. In QD sensitized cells and QD heterojunction cells using colloidal QDs well-controlled heterointerface and surface passivation are key issues for enhancement of photovoltaic performances. The improved performances of colloidal QDSCs are presented. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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“…For example, in the case of electron-based type-I systems, the valence band offset (VBO) (see Figure 2) is believed to produce an effective bandgap narrowing in terms of maximum attainable V OC . Under this line of thought, the V OC limitation would be similar to that occurring when a lower bandgap material is used as a barrier material between QD layers [30]. It has been suggested that type-II (staggered band lineup, Figure 2) QDs may be advantageous for the implementation of IBSCs, since they would not cause effective bandgap narrowing [29].…”

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confidence: 97%

Analysis of the intermediate-band absorption properties of type-II GaSb/GaAs quantum-dot photovoltaics

et al. 2017

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Quantum-dot (QD) intermediate-band (IB) materials are regarded as promising candidates for high-efficiency photovoltaics. The sequential two-step two-photon absorption processes that take place in these materials have been proposed to develop high-efficiency solar cells and infrared (IR) photodetectors. In this work, we experimentally and theoretically study the interrelation of the absorptivity with transitions of carriers to and from the IB in type II GaSb/GaAs QD devices. Our devices exhibit three optical bandgaps with: E L =0.49 eV, E H =1.02 eV and E G =1.52 eV, with the IB located 0.49 eV above the valence band. These values are well supported by semi-empirical calculations of the QDs electronic structure. Through intensity-dependent twophoton photocurrent experiments, we are able to vary the filling state of the IB, thus modifying the absorptivity of the transitions to and from this band. By filling the IB with holes via E=1.32 eV or E=1.93 eV monochromatic illumination, we demonstrate an increase in the E L-related absorptivity of more than two orders of magnitude and a decrease in the E H-related absorptivity of one order of magnitude. The anti-symmetrical evolution of those absorptivities is quantitatively explained by a photo-induced shift of the quasi-Fermi level of the IB. Furthermore, we report the observation of a two-photon photovoltage; i. e., the contribution of sub-bandgap two-photon absorption to increase the open-circuit voltage of solar cells. We find that the generation of the twophoton photovoltage is related, in general, to the production of a two-photon photocurrent. However, while photons with energy close to E L participate in the production of the two-photon photocurrent, they are not effective in the production of a two-photon photovoltage. We also report the responsivity of GaSb/GaAs QD devices performing as optically triggered photodetectors. These devices exhibit an amplification factor of almost 400 in the IR spectral region. This high value is achieved by minimizing-via doping-the absorptivity in the IR range of the QDs under equilibrium conditions. I. INTRODUCTION

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Voltage limitation analysis in strain-balanced InAs/GaAsN quantum dot solar cells applied to the intermediate band concept

Cited by 23 publications

References 25 publications

Wide-Bandgap InAs/InGaP Quantum-Dot Intermediate Band Solar Cells

Wide-Bandgap InAs/InGaP Quantum-Dot Intermediate Band Solar Cells

Recent progress on quantum dot solar cells: a review

Analysis of the intermediate-band absorption properties of type-II GaSb/GaAs quantum-dot photovoltaics

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