Increasing the Energy Gap between Band‐Edge and Trap States Slows Down Picosecond Carrier Trapping in Highly Luminescent InP/ZnSe/ZnS Quantum Dots

Sung, Young Mo; Kim, Tae-Gon; Yun, Dong‐Jin; Lim, Moo-Sup; Ko, Dong-Su; Jung, Chang Won; Won, Nayoun; Park, Sung-Jun; Jeon, Woo Sung; Lee, Hyo Sug; Kim, Jung-Hwa; Jun, Sangmi; Sul, Soohwan; Hwang, Sungwoo

doi:10.1002/smll.202102792

Cited by 31 publications

(35 citation statements)

References 60 publications

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“…As shown in Fig. 3c , the TA spectra of InP/ZnSe 0.7 S 0.3 /ZnS exhibited a slight shift of peaks for both PA and PB, which confirmed the restrain of the interface defects and featured layered quantum-well structure 41 , 45 – 47 . While the inner shell was tuned to InP/ZnSe/ZnS QDs as shown in Fig.…”

Section: Resultsmentioning

confidence: 61%

“…In the light of Fermi golden rule, the PL lifetime was in reverse proportion with the overlap of electron and hole functions 43 . As a result, the fast decay process was considered as band-edge emission because of the large overlap of electrons and holes whereas the slow decay process was considered as trap emission 41 , 44 . With the increasing ratio of Se/S element of ZnSe x S 1−x inner shell, the ratio of trap/band-edge emission gradually decreased from 40% to 14% until x = 0.7, then the ratio of trap/band-edge emission rose again (Table S4 in Supplementary Information).…”

Section: Resultsmentioning

confidence: 99%

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Highly efficient green InP-based quantum dot light-emitting diodes regulated by inner alloyed shell component

Cao

Shan³

et al. 2022

Light Sci Appl

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InP-based quantum dot light-emitting diodes (QLEDs), as less toxic than Cd-free and Pb-free optoelectronic devices, have become the most promising benign alternatives for the next generation lighting and display. However, the development of green-emitting InP-based QLEDs still remains a great challenge to the environmental preparation of InP quantum dots (QDs) and superior device performance. Herein, we reported the highly efficient green-emitting InP-based QLEDs regulated by the inner alloyed shell components. Based on the environmental phosphorus tris(dimethylamino)phosphine ((DMA)3P), we obtained highly efficient InP-based QDs with the narrowest full width at half maximum (~35 nm) and highest quantum yield (~97%) by inserting the gradient inner shell layer ZnSexS1−x without further post-treatment. More importantly, we concretely discussed the effect and physical mechanism of ZnSexS1–x layer on the performance of QDs and QLEDs through the characterization of structure, luminescence, femtosecond transient absorption, and ultraviolet photoelectron spectroscopy. We demonstrated that the insert inner alloyed shell ZnSexS1−x provided bifunctionality, which diminished the interface defects upon balancing the lattice mismatch and tailored the energy levels of InP-based QDs which could promote the balanced carrier injection. The resulting QLEDs applying the InP/ZnSe0.7S0.3/ZnS QDs as an emitter layer exhibited a maximum external quantum efficiency of 15.2% with the electroluminescence peak of 532 nm, which was almost the highest record of InP-based pure green-emitting QLEDs. These results demonstrated the applicability and processability of inner shell component engineering in the preparation of high-quality InP-based QLEDs.

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Section: Resultsmentioning

confidence: 61%

Section: Resultsmentioning

confidence: 99%

Highly efficient green InP-based quantum dot light-emitting diodes regulated by inner alloyed shell component

Cao

Shan³

et al. 2022

Light Sci Appl

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“…Recent work found that the shallow trap states are close to the conduction band edge and act as electron traps. [32] Here, the total PL QY was not strongly reliant on electron trapping. We ascertained that, in our case, the shell morphology control affects the PL QY as well as both hot hole trapping and electron trapping.…”

Section: Transient Absorption Spectroscopy and Hot Hole Trappingmentioning

confidence: 89%

“…Sung et al recently revealed that the shallow defect states leading to a partially trap emission in highly luminescent InP/ZnSe/ZnS QDs are associated with indium impurities in the ZnSe shell. [32] Weighting the preexponential factors by their associated lifetime and plotting versus wavelength presents the decay-associated spectra (DAS).…”

Section: Time-resolved Photoluminescence Spectra and The Correspondin...mentioning

confidence: 99%

Tuning Hot Carrier Dynamics of InP/ZnSe/ZnS Quantum Dots by Shell Morphology Control

Park

Won

Han

et al. 2021

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Auger recombination [12,13] and energy transfer between QDs in films, which is required in QD-light emitting diode (LED) applications. [14][15][16][17] Second is the etching of an oxidized core prior to shell growth to prevent interfacial oxidation. [7,18,19] Finally, smoothing of core/shell interface by matching a shell with a similar lattice constant can be applied to avoid the generation of defect sites. [20,21] We synthesize InP/ZnSe/ZnS QDs having a thick ZnSe shell (with 8 monolayers). The QDs with thick ZnSe shell are effective for reducing energy transfer between neighboring QDs in respect of QD-LED applications. In this study, we present a simple but highly effective strategy to modulate the InP/ZnSe/ZnS QD shapes by controlling the shell reaction temperatures. The strategy of increasing the ZnSe shell-grown temperature accelerated the rates of shell growth. The synthesized two structures showed differences in morphology; one is a QD with an irregular shell (iQD), and the other is one with a regular isotropic shell (rQD). Especially, the rQDs have significantly improved the photoluminescence (PL) quantum yield (QY). Since the correlation between morphology modification and photophysical properties has been unexplored for InP-based core/shell QDs to the best of our knowledge, we scrutinized the ZnSe shell crystalline structures and PL properties of the InP/ZnSe/ZnS QDs with different shapes.Ensemble-averaged measurements have often been used to evaluate QD photophysical properties, [22][23][24][25] but they tend to overlook the nature of an individual QD or inter-dot interactions. To fully understand the charge carrier dynamics depending on the QD morphology, we investigated the photophysical properties of QDs on both ensemble and single dot levels. As a result, it was found that the shape-dependent QD PL efficiencies are governed by charge trapping dynamics. The ZnSe crystalline structure analyses verified that the fast ZnSe reaction on the InP core reduced facet-selective growth and eliminated stacking faults. Thus, we have concluded that the enhancement of PL QY in isotropic QDs has resulted from the removal of stacking faults. The pump energy-dependent transient absorption (TA) dynamics showed that the hot hole trapping was considerably suppressed in the iQDs. This spectroscopic evidence supports the supposition that the stacking faults in the InP/ZnSe crystalline structures act as structural defects to trap hot charge carriers. In this study, we provide a spectroscopic insight into the shape-dependent PL efficiency of InP-based QDs and the correlation between the hole trapping dynamics and the structural defects.Isotropic InP/ZnSe/ZnS quantum dots (QDs) are prepared at a high reaction temperature, which facilitates ZnSe shell growth on random facets of the InP core. Fast crystal growth enables stacking faults elimination, which induces anisotropic growth, and as a result, improves the photoluminescence (PL) quantum yield by nearly 20%. Herein, the effect of the QD morphology on photophysical properti...

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“…However, the lattice mismatch of the core/shell structure implies more defects and prevents the formation of a perfect heteroepitaxial interface. In addition, broad emission originates from the luminescence of holes trapped by surface and lattice defects, resulting in spectral broadening [ 28 , 117 ]. For narrow linewidth InP QLED, the growth of InP QDs with high lattice integrity, uniformity, and high spherical symmetry is helpful to exhibit more excellent light-emitting properties.…”

Section: Challenge and Future Directionmentioning

confidence: 99%

Advances and Challenges in Heavy-Metal-Free InP Quantum Dot Light-Emitting Diodes

et al. 2022

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Light-emitting diodes based on colloidal quantum dots (QLEDs) show a good prospect in commercial application due to their narrow spectral linewidths, wide color range, excellent luminance efficiency, and long operating lifetime. However, the toxicity of heavy-metal elements, such as Cd-based QLEDs or Pb-based perovskite QLEDs, with excellent performance, will inevitably pose a serious threat to people’s health and the environment. Among heavy-metal-free materials, InP quantum dots (QDs) have been paid special attention, because of their wide emission, which can, in principle, be tuned throughout the whole visible and near-infrared range by changing their size, and InP QDs are generally regarded as one of the most promising materials for heavy-metal-free QLEDs for the next generation displays and solid-state lighting. In this review, the great progress of QLEDs, based on the fundamental structure and photophysical properties of InP QDs, is illustrated systematically. In addition, the remarkable achievements of QLEDs, based on their modification of materials, such as ligands exchange of InP QDs, and the optimization of the charge transport layer, are summarized. Finally, an outlook is shown about the challenge faced by QLED, as well as possible pathway to enhancing the device performance. This review provides an overview of the recent developments of InP QLED applications and outlines the challenges for achieving the high-performance devices.

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Increasing the Energy Gap between Band‐Edge and Trap States Slows Down Picosecond Carrier Trapping in Highly Luminescent InP/ZnSe/ZnS Quantum Dots

Cited by 31 publications

References 60 publications

Highly efficient green InP-based quantum dot light-emitting diodes regulated by inner alloyed shell component

Highly efficient green InP-based quantum dot light-emitting diodes regulated by inner alloyed shell component

Tuning Hot Carrier Dynamics of InP/ZnSe/ZnS Quantum Dots by Shell Morphology Control

Advances and Challenges in Heavy-Metal-Free InP Quantum Dot Light-Emitting Diodes

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