ZnTe/ZnSe (Core/Shell) Type-II Quantum Dots: Their Optical and Photovoltaic Properties

Bang, Jiwon; Park, Juwon; Lee, Ji Hwang; Won, Nayoun; Nam, Jutaek; Lim, Jongwoo; Chang, Byoung Yong; Lee, Hyo Joong; Chon, Bonghwan; Shin, Jae Won; Park, Jae Byung; Choi, Ji Ha; Cho, Kilwon; Park, Su Moon; Joo, Taiha; Kim, Sungjee

doi:10.1021/cm9027995

Cited by 179 publications

(164 citation statements)

References 46 publications

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“…The energy gap between the ZnSe conduction band and the ZnTe valence band is estimated at ~2.0 eV [52][53][54]69 (620 nm), which is close to the 612 nm emission peak that we observe in the orange emission shoulder. The slight shift can be attributed to strain as a result of epitaxial mismatch that could modulate the band structure.…”

Section: Acs Nanosupporting

confidence: 80%

“…49,50 Furthermore, theoretical and experimental reports concluded that when the two materials are interfaced, they form a p-n heterojunction with a type II band alignment, which can be exploited for photovoltaics and green electroluminescence. [51][52][53][54] The guided ZnSe@ZnTe core-shell nanowires grow horizontally and aligned as seen in the scanning electron microscope (SEM) image in figure 1B. Their orientation is determined by the interactions between a sapphire substrate and a ZnSe n-type core.…”

mentioning

confidence: 98%

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Surface-Guided Core–Shell ZnSe@ZnTe Nanowires as Radial p–n Heterojunctions with Photovoltaic Behavior

Oksenberg¹,

Martí‐Sánchez

Popovitz‐Biro³

et al. 2017

ACS Nano

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The organization of nanowires on surfaces remains a major obstacle toward their large-scale integration into functional devices. Surface−material interactions have been used, with different materials and substrates, to guide horizontal nanowires during their growth into well-organized assemblies, but the only guided nanowire heterostructures reported so far are axial and not radial. Here, we demonstrate the guided growth of horizontal core−shell nanowires, specifically of ZnSe@ZnTe, with control over their crystal phase and crystallographic orientations. We exploit the directional control of the guided growth for the parallel production of multiple radial p−n heterojunctions and probe their optoelectronic properties. The devices exhibit a rectifying behavior with photovoltaic characteristics upon illumination. Guided nanowire heterostructures enable the bottom-up assembly of complex semiconductor structures with controlled electronic and optoelectronic properties.

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Section: Acs Nanosupporting

confidence: 80%

mentioning

confidence: 98%

Surface-Guided Core–Shell ZnSe@ZnTe Nanowires as Radial p–n Heterojunctions with Photovoltaic Behavior

Oksenberg¹,

Martí‐Sánchez

Popovitz‐Biro³

et al. 2017

ACS Nano

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“…Packing additional ligands onto the CQD surface or growing a complete shell to passivate the core more fully can be expected to improve overall charge carrier lifetimes 38,43,44 . In addition, unintentionally introduced impurities presented at the time of synthesis or deposition represent a little-explored potential source of midgap trap states [45][46][47][48] .…”

Section: Discussionmentioning

confidence: 99%

Engineering colloidal quantum dot solids within and beyond the mobility-invariant regime

et al. 2014

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Colloidal quantum dots are attractive materials for efficient, low-cost and facile implementation of solution-processed optoelectronic devices. Despite impressive mobilities (1-30 cm 2 V À 1 s À 1 ) reported for new classes of quantum dot solids, it is-surprisingly-the much lower-mobility (10 À 3 -10 À 2 cm 2 V À 1 s À 1 ) solids that have produced the best photovoltaic performance. Here we show that it is not mobility, but instead the average spacing among recombination centres that governs the diffusion length of charges in today's quantum dot solids. In this regime, colloidal quantum dot films do not benefit from further improvements in charge carrier mobility. We develop a device model that accurately predicts the thickness dependence and diffusion length dependence of devices. Direct diffusion length measurements suggest the solid-state ligand exchange procedure as a potential origin of the detrimental recombination centres. We then present a novel avenue for in-solution passivation with tightly bound chlorothiols that retain passivation from solution to film, achieving an 8.5% power conversion efficiency.

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“…2 Similar effects, combined with a decrease in the Auger recombination rate were observed for CdTe/CdSe QDs. 3,4 For CdSe/CdTe heteronanocrystals 5,6 and ZnTe/ZnSe QDs, 7 long radiative lifetimes, indicative of charge separation, and a strong redshift of the exciton transitions were reported.…”

mentioning

confidence: 99%

The Different Nature of Band Edge Absorption and Emission in Colloidal PbSe/CdSe Core/Shell Quantum Dots

et al. 2010

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We present a quantitative analysis of the absorption and luminescence of colloidal PbSe/CdSe core/shell quantum dots (QDs). In absorption, both the energy and the oscillator strength of the first exciton transition coincide with that of plain PbSe QDs. In contrast, luminescence lifetime measurements indicate that the oscillator strength of the emitting transition is reduced by at least a factor of 4 compared to PbSe core QDs. Moreover, the addition of an electron scavenger quenches the PbSe/CdSe emission, while a hole scavenger does not. This implies that the electron wave function reaches the QD surface, while the hole is confined to the PbSe core. These observations are consistent with calculations based on the effective mass model, which show that PbSe/CdSe QDs are at the boundary between the type-I and quasi-type-II regime, where the electron spreads over the entire nanoparticle and the hole remains confined in the PbSe core. However, as this only leads to a minor reduction of the oscillator strength, it follows that the drastic reduction of the oscillator strength in emission cannot be explained in terms of electron delocalization. In combination with the increased Stokes shift for PbSe/ CdSe QDs, this indicates that the emission results from lower energy states that are fundamentally different from the absorbing states.

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ZnTe/ZnSe (Core/Shell) Type-II Quantum Dots: Their Optical and Photovoltaic Properties

Cited by 179 publications

References 46 publications

Surface-Guided Core–Shell ZnSe@ZnTe Nanowires as Radial p–n Heterojunctions with Photovoltaic Behavior

Surface-Guided Core–Shell ZnSe@ZnTe Nanowires as Radial p–n Heterojunctions with Photovoltaic Behavior

Engineering colloidal quantum dot solids within and beyond the mobility-invariant regime

The Different Nature of Band Edge Absorption and Emission in Colloidal PbSe/CdSe Core/Shell Quantum Dots

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