Role of charge separation on two-step two photon absorption in InAs/GaAs quantum dot intermediate band solar cells

Cretı̀, Arianna; Tasco, V.; Cola, A.; Montagna, G.; Tarantini, Iolena; Salhi, A.; Al-Muhanna, A.; Passaseo, A.; Lomascolo, M.

doi:10.1063/1.4941793

Cited by 25 publications

(17 citation statements)

References 32 publications

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“…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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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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confidence: 99%

Two-step photon up-conversion solar cells

et al. 2017

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“…(2) After carriers escape from QD, the carriers may be recaptured and recombine in the wetting layer and QDs. 48 Increased electric field improves the charge separation 10 and reduces the number of carriers within the QD region, so the carrier collection increases with increasing electric field. (3) Although the QCSE reduces the absorption rate in the QD ground state 46 due to spatial separation of electron and hole wave-function, the associated increasing radiative recombination lifetime of the ground state carriers may contribute to enhanced carrier collection.…”

Section: B Experimentsmentioning

confidence: 99%

“…This demonstrates that an increasing electric field increases the radiative recombination lifetime by partially separating the electron and hole wavefunctions in the ground state along the growth direction. 10,18 A half-filled carrier population in the IB is required for TSPA to allow optical transitions of carriers both into and out of the confined states. The IB with partially filled electrons requires reduced radiative recombination and suppressed carrier escape.…”

Section: B Experimentsmentioning

confidence: 99%

“…6 To enable quasi-Fermi level splitting between IB and CB, thermal escape should be suppressed. Therefore, although experimental observation of the second photon absorption has been observed at both low temperature [9][10][11] and room temperature, [12][13][14] the voltage preservation so far has only been shown at low temperature. 15,16 To increase the a) Now at Finisar Corporation.…”

Section: Introductionmentioning

confidence: 99%

“…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. 18 Obviously, the electric field significantly affects TSPA efficiency and the performances of QD-IBSCs.…”

Section: Introductionmentioning

confidence: 99%

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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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Recent advances on portable photoelectrochemical biosensors for diagnostics

Wu,

Tang

2023

Electroanalysis

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Efficient and accurate diagnostic methods are important for human health monitoring and prevention of major diseases, so the establishment of efficient and convenient testing methods for clinical diagnosis is urgent. Photoelectrochemical (PEC) biosensors have attracted much attention because of their high sensitivity, low detection background, and especially the advantages of combining photoexcitation and electrochemical detection. With the rapid development of integrated circuit technology many wireless transmissions of highly aggregated portable micro devices are manufactured, its small size, easy to carry, and the ability to visualize the results of the test is shown to be the potential for the application of such devices. This review aims to cover recent advances in PEC biosensing within the field of portable detection, including the principles of PEC biosensors, common photovoltaic materials, and scalable fabrication techniques for portable PEC biosensing. Future prospects in the field are also discussed.

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Role of charge separation on two-step two photon absorption in InAs/GaAs quantum dot intermediate band solar cells

Cited by 25 publications

References 32 publications

Two-step photon up-conversion solar cells

Two-step photon up-conversion solar cells

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

Recent advances on portable photoelectrochemical biosensors for diagnostics

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