Impurity Sub-Band in Heavily Cu-Doped InAs Nanocrystal Quantum Dots Detected by Ultrafast Transient Absorption

Yang, Chunfan; Faust, Adam; Amit, Yorai; Gdor, Itay; Banin, Uri; Ruhman, Sanford

doi:10.1021/acs.jpca.5b10682

Cited by 14 publications

(27 citation statements)

References 49 publications

(120 reference statements)

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“…Although the PL dynamics of copper-doped semiconductor NCs have been described in many publications, their TA spectra and dynamics contain a large amount of mechanistic information but have not yet been thoroughly explored. Exciton TA data from InAs NCs doped with interstitial copper as shallow donors have been reported, 43 but those samples apparently represent a very different electronic structure from the luminescent copper-doped NCs investigated here. Transient X-ray absorption data for copper-doped CdS NCs have been reported 10 that support the photophysical mechanism described by Scheme 1, showing both copper oxidation and the appearance of new pre-edge 1s → 3d transitions at the copper K edge.…”

Section: Discussionmentioning

confidence: 60%

Photodoping and Transient Spectroscopies of Copper-Doped CdSe/CdS Nanocrystals

2018

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Colloidal Cu-doped CdSe/CdS core/shell semiconductor nanocrystals (NCs) are investigated in their as-prepared and degenerately n-doped forms using time-resolved photoluminescence and transient-absorption spectroscopies. Photoluminescence from Cu:CdSe/CdS NCs is dominated by recombination of delocalized conduction-band (CB) electrons with copper-localized holes. In addition to prominent bleaching of the first excitonic absorption feature, transient-absorption measurements show bleaching of the sub-bandgap copper-to-CB charge-transfer (MLCT) absorption band and also reveal a photoinduced midgap valence-band (VB)-to-copper charge-transfer (LMCT) absorption band that extends into the near-infrared, as predicted by recent computations. The photoluminescence of these NCs is substantially diminished upon introduction of excess CB electrons via photodoping. Time-resolved photoluminescence measurements reveal that the MLCT excited state is still formed upon photoexcitation of the n-doped Cu:CdSe/CdS NCs, but its luminescence is quenched by a fast (picosecond) three-carrier trap-assisted Auger recombination process involving two CB electrons and one copper-bound hole.

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Section: Discussionmentioning

confidence: 60%

Photodoping and Transient Spectroscopies of Copper-Doped CdSe/CdS Nanocrystals

2018

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“…These levels are occupied by the excess charge carriers, resulting in a shift (blue shift) in the absorption spectra (widening of the band gap), which is known as the Burstein−Moss effect. 19,20 The simulated density of state (DOS) diagram shows the presence of additional state within the band gap for S-modified samples shown in Figure S2d,e. Upon further increase of the carrier concentration, the band gap becomes narrow due to the correlated motion of the charge carriers and their scattering by ionized impurities.…”

Section: Resultsmentioning

confidence: 99%

“…It is well-known that upon increasing the dopant concentration, the impurity levels interact with each other to form a bandlike structure close to the band edge within the band gap of the host that depends on the type of doping (conduction band and n-type doping and valence band and p-type doping). These levels are occupied by the excess charge carriers, resulting in a shift (blue shift) in the absorption spectra (widening of the band gap), which is known as the Burstein–Moss effect. , The simulated density of state (DOS) diagram shows the presence of additional state within the band gap for S-modified samples shown in Figure S2d,e. Upon further increase of the carrier concentration, the band gap becomes narrow due to the correlated motion of the charge carriers and their scattering by ionized impurities .…”

Section: Resultsmentioning

confidence: 99%

Stabilization of Lead–Tin-Alloyed Inorganic–Organic Halide Perovskite Quantum Dots

Mehta

Kim

et al. 2018

ACS Nano

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Recently, lead−tin-based alloyed halide perovskite quantum dots (QDs) with improved stability and less toxicity have been introduced. However, the perovskite QDs containing tin are still unstable and exhibit low photoluminescence quantum yields (PLQYs), owing to the presence of defects in the alloyed system. Here, we have attempted to introduce sulfur anions (S 2− ) into the host lattice (MAPb 0.75 Sn 0.25 Br 3 ) as a promising route to stable alloyed perovskite QDs with improved stability and PLQY. In this study, we used elemental sulfur as a sulfur precursor. The successful incorporation of sulfur anions into the host lattice resulted in a highly improved PLQY (>75% at room temperature), which is believed to be due to a reduction in the defect-related non-radiative recombination centers present in the host lattice. Furthermore, we found that the emission property could be tuned between the bright green and cyanbluish regions without compromising on color quality. This work invigorates the perovskite research community to prepare stable, bright, and color-tunable alloyed inorganic−organic perovskite QDs without compromising on their phases and color quality, which can lead to considerable advances in display technology.

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“…[21,[47][48][49][50] The Cu doped-InAs NCs FETs showed improved performance over the intrinsic InAs films due to electron donating impurity sub-band, in line with the n-type doping characteristics at the individual nanocrystal level. [21,49,51] However, the fabrication of p-type InAs NCs FETs is challenging as one has to overcome the intrinsic excess free electrons of as-synthesized InAs NCs.…”

Section: Introductionmentioning

confidence: 99%

InAs Nanocrystals with Robust p‐Type Doping

Asor

Liu

Ossia

et al. 2020

Adv Funct Materials

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Robust control over the carrier type is fundamental for the fabrication of nanocrystal‐based optoelectronic devices, such as the p–n homojunction, but effective incorporation of impurities in semiconductor nanocrystals and its characterization is highly challenging due to their small size. Herein, InAs nanocrystals (NCs), post‐synthetically doped with Cd, serve as a model system for successful p‐type doping of originally n‐type InAs nanocrystals, as demonstrated in field effect transistors (FETs). Advanced structural analysis, using atomic resolution electron microscopy and synchrotron X‐ray absorption fine structure spectroscopy reveal that Cd impurities reside near and on the nanocrystal surface acting as substitutional p‐dopants replacing Indium. Commensurately, Cd‐doped InAs FETs exhibit remarkable stability of their hole conduction, mobility, and hysteretic behavior over time when exposed to air, while intrinsic InAs NCs FETs are easily oxidized and their performance quickly declines. Therefore, Cd plays a dual role acting as a p‐type dopant, and also protects the nanocrystals from oxidation, as evidenced directly by X‐ray photoelectron spectroscopy measurements of air exposed samples of intrinsic and Cd‐doped InAs NCs films. This study demonstrates robust p‐type doping of InAs nanocrystals, setting the stage for implementation of such doped nanocrystal systems in printed electronic devices.

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Impurity Sub-Band in Heavily Cu-Doped InAs Nanocrystal Quantum Dots Detected by Ultrafast Transient Absorption

Cited by 14 publications

References 49 publications

Photodoping and Transient Spectroscopies of Copper-Doped CdSe/CdS Nanocrystals

Photodoping and Transient Spectroscopies of Copper-Doped CdSe/CdS Nanocrystals

Stabilization of Lead–Tin-Alloyed Inorganic–Organic Halide Perovskite Quantum Dots

InAs Nanocrystals with Robust p‐Type Doping

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