An investigation into the effective surface passivation of quantum dots by a photo-assisted chemical method

Joo, Soyeong; Park, Hyun-Su; Kim, Do-Yeon; Kim, Bum-Sung; Lee, Chan Gi; Kim, Woo‐Byoung

doi:10.1063/1.5009788

Cited by 5 publications

(3 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In order to understand more details and the mechanism of QD oxidation in relation to the PL characteristics, some oxidizing agents such as hydrogen peroxide or HOCl were employed to test pure CdSe or other surface-modified QDs in the controlled conditions, in which the results showed that severe degradation and surface dissolution of the QDs did occur along with the change of luminescence properties. − A theoretical study of CdSe QDs also exhibited that the oxidation destroyed the perfection of the QD surface and resulted in a near-infrared transition in relation to Se–O antibonding, which further changed the luminescence properties . However, it is controversial that some groups found oxidation of CdSe could lead to some increase of PL QY and red shift of PL emission, , which may indicate that the oxidation mechanism of QDs is complicated and would be determined by QD types and oxidation conditions. Regardless of PL characteristics, the oxidation of CdSe QDs is generally simply correlated to formation of SeO 2 together with QD surface damage, though further detailed oxidation mechanism and the relation to PL remain unclear.…”

Section: Introductionmentioning

confidence: 99%

“…30−32 A theoretical study of CdSe QDs also exhibited that the oxidation destroyed the perfection of the QD surface and resulted in a near-infrared transition in relation to Se−O antibonding, which further changed the luminescence properties. 33 However, it is controversial that some groups found oxidation of CdSe could lead to some increase of PL QY and red shift of PL emission, 34,35 which may indicate that the oxidation mechanism of QDs is complicated and would be determined by QD types and oxidation conditions. Regardless of PL characteristics, the oxidation of CdSe QDs is generally simply correlated to formation of SeO 2 together with QD surface damage, though further detailed oxidation mechanism and the relation to PL remain unclear.…”

Section: ■ Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Inhibiting the Surface Oxidation of Low-Cadmim-Content ZnS:(Cd,Se) Quantum Dots for Enhancing Application Reliability

Yeh

Chen

et al. 2019

ACS Appl. Nano Mater.

View full text Add to dashboard Cite

Quantum dots (QDs) are advancing display and innovating lighting but still encountering unsolved stability problems mainly caused by material oxidation. In this work, the effect of Se composition (0.8 at. % vs 4.3 at. %) and thick ZnS shell (shell thickness ∼ 5 nm) on the oxidation of low-Cd content ZnS:(Cd,Se) QDs (Cd, <20 at. %) were investigated. Surface analysis and thermodynamic calculation were employed to study the QD oxidation. The results show that the oxidation products were correlated to (Zn,Cd)SO4, (Zn,Cd)(OH)2, and SeO2 phases, which lead to QD surface defects/amorphization inducing ligand detachment and particle agglomeration, indicating that the shell should be a much more dominant role in the QD reliability. It was also found that a heavier Se doping and thicker ZnS overcoating indeed prevented the oxidation of Cd, Zn, and S so the low-Cd QD stability could be improved. By considering the application criteria, optimized green QDs with diameter of ∼12 nm and chemical composition of Zn0.443S0.463:Cd0.057Se0.037 are suggested for QD-based lighting and displays. A QD color enhancement film based on low-Cd QDs exhibited superior stability compared with a commercial product, demonstrating their potential in practical applications.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Inhibiting the Surface Oxidation of Low-Cadmim-Content ZnS:(Cd,Se) Quantum Dots for Enhancing Application Reliability

Yeh

Chen

et al. 2019

ACS Appl. Nano Mater.

View full text Add to dashboard Cite

show abstract

“…Secondly, Jin et al, 2006 [ 85 ] showed that the presence of a new layer of a different material on the surface of QD can cause a red shift due to a decrease in the bandgap. On the other hand, other researchers such as Joo et al, 2018 [ 86 ] proved that the adsorption of other chemical groups can cause surface defect passivation. This can result in a blue shift due to increasing bandgap.…”

Section: Optical Sensorsmentioning

confidence: 99%

Nanomaterial-Based CO2 Sensors

2020

View full text Add to dashboard Cite

The detection of carbon dioxide (CO2) is critical for environmental monitoring, chemical safety control, and many industrial applications. The manifold application fields as well as the huge range of CO2 concentration to be measured make CO2 sensing a challenging task. Thus, the ability to reliably and quantitatively detect carbon dioxide requires vastly improved materials and approaches that can work under different environmental conditions. Due to their unique favorable chemical, optical, physical, and electrical properties, nanomaterials are considered state-of-the-art sensing materials. This mini-review documents the advancement of nanomaterial-based CO2 sensors in the last two decades and discusses their strengths, weaknesses, and major applications. The use of nanomaterials for CO2 sensing offers several improvements in terms of selectivity, sensitivity, response time, and detection, demonstrating the advantage of using nanomaterials for developing high-performance CO2 sensors. Anticipated future trends in the area of nanomaterial-based CO2 sensors are also discussed in light of the existing limitations.

show abstract

Electrochemical Charging Effect on the Optical Properties of InP/ZnSe/ZnS Quantum Dots

Park

Won

Kim

et al. 2020

Small

View full text Add to dashboard Cite

fabrication of blue-emitting Cd-free QDs are still under development. [7-10] Above all, the charging of QDs is an obstacle for manufacturing QD-LEDs with good performance. [11] The simple mechanism of EL is that electrons and holes are formed by charge injection, and light is generated by the electron-hole pair recombination. Hence, it is essential to understand the charging process by mimicking EL processes. The complementary combination of spectroscopic technology and electrochemical control helps emulate EL and explain the charging process whether the charges occupy quantum states or trap states. Recently, there has been an increase in research to improve QD luminescence capabilities and charge extraction properties by performing electrochemical charging studies on QD films. [1,12,13] Li et al. [13] have shown that electron injection into the ground excitonic state of CdSe/CdS QDs leads to the bleaching of 1S 3/2 1S e transition because of 1S e state filling. Qin et al. [14] have investigated how the photoluminescence (PL) lifetime changes in CdSeS/ZnS QD under electrochemical control with blinking dynamics. Gooding et al. [15] have studied the effects of hole and electron injection on the PL of CdSe/ CdS/ZnS QDs. Many studies have revealed the effect of electron injection on the optical properties in Cd-based QDs, which leads to environmental issues. Environmentally friendly III-V semiconductors, especially InP QDs, have recently emerged as the best alternative to toxic II-VI semiconductors. [16-17] Meanwhile, the surfaces of InP core QDs are easily oxidized when they are exposed to oxygen environments. As a countermeasure, overcoating nanocrystals with wider band-gap materials has proven to be the best option to increase stability against photo-oxidation and to enhance the photoluminescence quantum yield (PL QY). [5,18,19] For example, the inorganic core can be surrounded by the shell, such as ZnSe and ZnS. [20] Möbius et al. reported that the electrical charges generated by application of a mechanical load are injected into the QDs, leading to PL quenching in InP/ZnS-based device. [17] However, the spectroelectrochemical properties were not yet reported in InP QDs to the best of our knowledge. Recently, we have reported highly luminescent InP/ZnSe/ZnS QDs synthesized with as much high efficiency as state-of-the-art Cd-based QDs. [21] In this study, we analyze the spectroelectrochemical properties depending on mid-shell thickness to identify the effect of charging on highly luminescent InP Semiconductor quantum dots (QDs) are spotlighted as a key type of emissive material for the next generation of light-emitting diodes (LEDs). This work presents the investigation of the electrochemical charging effect on the absorption and emission of the InP/ZnSe/ZnS QDs with different mid-shell thicknesses. The excitonic peak is gradually bleached during electrochemical charging, which is caused by 1S e (or 1S h) state filling when the electron (or hole) is injected into the InP core. Additional charges also lead to photo...

show abstract

An investigation into the effective surface passivation of quantum dots by a photo-assisted chemical method

Cited by 5 publications

References 28 publications

Inhibiting the Surface Oxidation of Low-Cadmim-Content ZnS:(Cd,Se) Quantum Dots for Enhancing Application Reliability

Inhibiting the Surface Oxidation of Low-Cadmim-Content ZnS:(Cd,Se) Quantum Dots for Enhancing Application Reliability

Nanomaterial-Based CO2 Sensors

Electrochemical Charging Effect on the Optical Properties of InP/ZnSe/ZnS Quantum Dots

Contact Info

Product

Resources

About