Theoretical Study on Effect of SiC Crystal Structure on Carrier Transfer in Quantum Dot Solar Cells

Hirose, Shigeo; Yamashita, Ikuo; Nagumo, Ryo; Miura, Ryuji; Suzuki, Ai; Tsuboi, Hideyuki; Hatakeyama, Nozomu; Endou, Akira; Takaba, Hiromitsu; Kubo, Momoji; Miyamoto, Akira

doi:10.7567/jjap.50.04dp05

Cited by 3 publications

(4 citation statements)

References 31 publications

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“…5 Potential sources of this discrepancy include the formation of surface oxides 49 and associated interfacial charge recombination, 50 as well as other surface defects. Another cause could be the large number of twin defects observed in experimental NWs 9,10,51 and associated {111} sidewall facets.…”

Section: B Charge-recombination Dynamicsmentioning

confidence: 99%

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Enhanced charge recombination due to surfaces and twin defects in GaAs nanostructures

Brown

Sheng

Shimamura

et al. 2015

Journal of Applied Physics

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Power conversion efficiency of gallium arsenide (GaAs) nanowire (NW) solar cells is severely limited by enhanced charge recombination (CR) at sidewall surfaces, but its atomistic mechanisms are not well understood. In addition, GaAs NWs usually contain a high density of twin defects that form a twin superlattice, but its effects on CR dynamics are largely unknown. Here, quantum molecular dynamics (QMD) simulations reveal the existence of an intrinsic type-II heterostructure at the (110) GaAs surface. Nonadiabatic quantum molecular dynamics (NAQMD) simulations show that the resulting staggered band alignment causes a photoexcited electron in the bulk to rapidly transfer to the surface. We have found orders-of-magnitude enhancement of the CR rate at the surface compared with the bulk value. Furthermore, QMD and NAQMD simulations show unique surface electronic states at alternating (111)A and (111)B sidewall surfaces of a twinned [111]-oriented GaAs NW, which act as effective CR centers. The calculated large surface recombination velocity quantitatively explains recent experimental observations and provides microscopic understanding of the underlying CR processes. V C 2015 AIP Publishing LLC. [http://dx.

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Section: B Charge-recombination Dynamicsmentioning

confidence: 99%

“…Other potential causes of the large SRV include the formation of surface oxides 49 and associated interfacial CR as mentioned before. 50 The high SRV of a twinned GaAs NW may be understood as a consequence of the unique electronic structures associated with its geometry (Fig. 7).…”

Section: Surface Recombination Velocitymentioning

confidence: 99%

Enhanced charge recombination due to surfaces and twin defects in GaAs nanostructures

Brown

Sheng

Shimamura

et al. 2015

Journal of Applied Physics

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“…An electron inside a QD cannot move freely in all directions, so it behaves like an atom, which provides the opportunity to control the energy carrier states. With such QDs spaced sufficiently close together forming a quasi‐crystal structure, overlap of the wave functions of quantum‐confined carriers in adjacent dots enables the formation of a real QD super lattice (QDSL) with the confined states smearing out to form a miniband . Conventional molecular beam epitaxy technology, although well‐developed, can achieve only very limited control along the growth direction, which induces a mixture state from the wet layer.…”

Section: Introductionmentioning

confidence: 99%

Impact of silicon quantum dot super lattice and quantum well structure as intermediate layer on p‐i‐n silicon solar cells

Rahman

Lee

Tsai

et al. 2015

Progress in Photovoltaics

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The photovoltaic effect of the silicon (Si)/silicon carbide (SiC) quantum dot super lattice (QDSL) and multi-quantum well (QW) strucutres is presented based on numerical simulation and experimental studies. The QDSL and QW structures act as an intermediate layer in a p-i-n Si solar cell. The QDSL consists of a stack of four 4-nm Si nano disks and 2-nm SiC barrier layers embedded in a SiC matrix fabricated with a top-down etching process. The Si nano disks were observed with bright field-scanning transmission electron microscopy. The simulation results based on the 3D finite element method confirmed that the quantum effect on the band structure for the QDSL and QW structures was different and had different effects on solar cell operation. The effect of vertical wave-function coupling to form a miniband in the QDSL was observed based on the solar-cell performance, showing a dramatic photovoltaic response in generating a high photocurrent density

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“…10 Potential causes of the large SRV include the formation of surface oxides 11 and associated interfacial CR. 12 However, the effect of ubiquitous TSLs on SRV remains elusive. Fundamental scientific questions are: What is the effect of TSLs on surface electronic states, and how do they influence the SRV in GaAs NWs?…”

mentioning

confidence: 99%

Twin superlattice-induced large surface recombination velocity in GaAs nanostructures

Sheng

Brown

Shimojo

et al. 2014

Applied Physics Letters

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Semiconductor nanowires (NWs) often contain a high density of twin defects that form a twin superlattice, but its effects on electronic properties are largely unknown. Here, nonadiabatic quantum molecular dynamics simulation shows unique surface electronic states at alternating (111)A and (111)B sidewall surfaces of a twinned [111]-oriented GaAs NW, which act as effective charge-recombination centers. The calculated large surface recombination velocity quantitatively explains recent experimental observations and provides microscopic understanding of the underlying surface-recombination processes.

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Theoretical Study on Effect of SiC Crystal Structure on Carrier Transfer in Quantum Dot Solar Cells

Cited by 3 publications

References 31 publications

Enhanced charge recombination due to surfaces and twin defects in GaAs nanostructures

Enhanced charge recombination due to surfaces and twin defects in GaAs nanostructures

Impact of silicon quantum dot super lattice and quantum well structure as intermediate layer on p‐i‐n silicon solar cells

Twin superlattice-induced large surface recombination velocity in GaAs nanostructures

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