Quantum Dot Materials Research Articles

Improvement of photoluminescence efficiency and photoelectricity performances of InP quantum dots through the passivation of surface defects

At present, InP quantum dot-sensitized solar cells (QDSSCs) still show moderate power conversion efficiency (PCE), because of charge recombination on the surface defects. Herein, we report a method to reduce the surface defects of InP quantum dots by Ga-doped and ZnS shell coating, which improves the performance of InP QDSSCs. Simultaneous enhancement of photoluminescence (PL) and photo-electricity performance of Ga doped InP (Ga:InP) quantum dots (QDs), Ga:InP/ZnS core/shell QDs were achieved. The maximum PL quantum yield of Ga:InP QDs and Ga:InP/ZnS QDs reached 14.9% and 76%, respectively. The maximum PCE value of Ga:InP and Ga:InP/ZnS QDSSCs reached 3.0% and 4.5% under 1 sun illumination (AM 1.5 G, 100 mW/cm2), respectively. The J-V curve revealed that Ga doping and ZnS shell coating reduced the surface recombination and increased the cell efficiency and stability. These results provided a new approach to obtaining quantum dot materials with high luminescence properties or good solar cell performances.

Monolithic Integration of Full-Color Microdisplay Screen with Sub-5µm Quantum-Dot Pixels.

Monolithic integration of color-conversion materials onto blue-backlight micro-light-emitting-diodes (micro-LEDs) has emerged as a promising strategy for achieving full-color microdisplay devices. However, this approach still encounters challenges such as the blue-backlight leakage and the poor fabrication yield rate due to unsatisfied quantum dot (QD) material and fabrication process. Here, the monolithic integration of 0.39-inch micro-display screens displaying colorful pictures and videos are demonstrated, which are enabled by creating interfacial chemical bonds for wafer-scale adhesion of sub-5 µm QD-pixels on blue-backlight micro-LED wafer. The ligand molecule with chlorosulfonyl and silane groups is selected as the synthesis ligand and surface treatment material, facilitating the preparation of high-efficiency QD photoresist and the formation of robust chemical bonds for pixel integration. This is a leading record in micro-display devices achieving the highest brightness larger than 400 thousand nits, the ultrahigh resolution of 3300 PPI, the wide color gamut of 130.4% NTSC, and the ultimate performance of service life exceeding 1000h. These results extend the mature integrated circuit technique into the manufacture of micro-display device, which also lead the road of industrialization process of full-color micro-LEDs.

High power lateral coupled InAs/GaAs quantum dot distributed feedback lasers grown on Si(001) substrates

High-quality single-frequency semiconductor lasers play a key role in silicon optical integrated systems. Combining high density 8-stacked quantum dot (QD) material and low–loss laterally coupled gratings, we here demonstrate a high output power, low noise, and insensitivity to light feedback 1.3 µm InAs/GaAs QD distributed feedback (DFB) laser grown on Si(001) substrates. For a QD DFB laser of a 3 × 1500 µm2 cavity, it exhibits a high single-mode output light power of up to 25 mW at 20 °C and 1.8 mW at 70 °C, respectively and maintains a stable single–mode operation in the entirely measured temperature range with a maximum side mode suppression ratio (SMSR) of 56.5 dB. Furthermore, the laser has an average relative intensity noise value low to –155.9 dB/Hz and a Lorentzian linewidth narrow to 243 kHz. In addition, the laser shows an insensitivity to optical feedback with a feedback level of –24.9 dB. Lastly, a 7-channel QD DFB laser array emitting at wavelengths from 1274.5 nm to 1290.0 nm are also exhibited with all SMSRs of higher than 45 dB. The results achieved here enable a practical single-frequency Si-based light source for the development of high-performance silicon photonic chips.

On the glow of cremated remains: long-lived green photo-luminescence of heat-treated human bones.

The long-lived green luminescence of human bone (that has been heated to 600°C for a short duration) is attributed to a carbon quantum dot material (derived from collagen) encapsulated and protected by an inorganic matrix (derived from bone apatite) and is more intense in dense rigid and crystalline parts of (healthy) human bones. The strong collagen-apatite interaction results (upon decomposition) in a protective inorganic environment of the luminescent centers allowing long-lived triplet-based emission of a carbon (quantum) dot-like material at room temperature, as well as resilience against oxidation between 550 and 650°C. The graphitic black phase (obtained upon heating around 400°C) is a precursor to the luminescent carbon-based material, that is strongly interacting with the crystalline inorganic matrix. Human bone samples that have been heated to 600°C were subjected to steady-state and time-resolved spectroscopy. Excitation-emission matrix (EEM) luminescence spectroscopy revealed a broad range of excitation and emission wavelengths, indicating a heterogeneous system with a broad density of emissive states. The effect of low temperature on the heat-treated bone was studied with Cryogenic Steady State Luminescence Spectroscopy. Cooling the bone to 80K leads to a slight increase in total emission intensity as well as an intensity increase towards to red part of the spectrum, incompatible with a defect state model displaying luminescent charge recombination in the inorganic matrix. Time-resolved spectroscopy with an Optical Multichannel Analyzer (OMA) and Time Correlated Single Photon Counting (TCSPC) of these samples showed that the decay could be fitted with a multi-exponential decay model as well as with second-order decay kinetics. Confocal Microscopy revealed distinct (plywood type) structures in the bone and high intensity-fast decay areas as well as a spatially heterogeneous distribution of green and (fewer) red emissive species. The use of the ATTO 565 dye aided in bone-structure visualization by chemical adsorption. Conceptually our data interpretation corresponds to previous reports from the material science field on luminescent powders.

Facile synthesis of yellow emissive heteroatom doped carbon quantum dots fluorescent probe with superior quantum yield for fast-track ionic detection in aqueous media

In this work, heteroatom (B and N) doped carbon quantum dots (CQDs) materials were synthesized via facile hydrothermal method using o-phenylenediamine (o-PD) as a nitrogen source and 3-aminophenyl boronic acid (3APBA) as a boron source. The synthesis parameters were optimized and optimal synthesis temperature and reaction time were 260 °C and 2 h, respectively. The chemical structures were characterized using various techniques. The experimental results showed that B,N co-doped CQDs had the strongest fluorescence intensity when the weight ratio of 3APBA:o-PD was 3:1 and showed a phenomenal quantum yield of 59% with high selectivity for Fe3+ and Hg2+ ions, with quenching constants 1.25 × 103 M–1 and 8.3 × 103 M–1, respectively. The high fluorescence quenching was attributed to the photoinduced electron transfer phenomenon, making it suitable for fluorescent sensing materials. Cytotoxicity data revealed synthesized materials are safe for biomedical applications within a 1–10 µg/mL concentration.

Advancing Silver Bismuth Sulfide Quantum Dots for Practical Solar Cell Applications.

Colloidal quantum dots (CQDs) show unique properties that distinguish them from their bulk form, the so-called quantum confinement effects. This feature manifests in tunable size-dependent band gaps and discrete energy levels, resulting in distinct optical and electronic properties. The investigation direction of colloidal quantum dots (CQDs) materials has started switching from high-performing materials based on Pb and Cd, which raise concerns regarding their toxicity, to more environmentally friendly compounds, such as AgBiS2. After the first breakthrough in solar cell application in 2016, the development of AgBiS2 QDs has been relatively slow, and many of the fundamental physical and chemical properties of this material are still unknown. Investigating the growth of AgBiS2 QDs is essential to understanding the fundamental properties that can improve this material's performance. This review comprehensively summarizes the synthesis strategies, ligand choice, and solar cell fabrication of AgBiS2 QDs. The development of PbS QDs is also highlighted as the foundation for improving the quality and performance of AgBiS2 QD. Furthermore, we prospectively discuss the future direction of AgBiS2 QD and its use for solar cell applications.

ZBS glass synthesized containing both Eu3+-Eu2+ CsPbBr3 quantum dots with multi-color luminescence for white LEDs

In this article, zinc-borosilicate silicon（ZBS） glass containing europium (Eu) ions and CsPbBr3 quantum dots (QDs) (ZEQ) was synthesized via melting crystallization route. The composition and luminescent properties are investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and photoluminescence (PL) spectra. The XRD and XPS results imply that Eu 3+, Eu 2+ ions and CsPbBr3 QDs are coexisted in ZBS glass. The dual-mode emission from cyan to orange-red can be achieved by adjusting the melting temperature. Besides, the ZEQ has good water resistance, outstanding light irradiation and excellent heating-cooling cycle stability. Moreover, based on the ZEQ, the light-emitting diodes (LEDs) are designed to obtain the white light with the correlated color temperature (CCT) of 5255 K, the Coherent Infrared Energy (CIE) color coordinate of (0.337 0.313), the NSCT color gamut of 116 % and 87 % of Rec.2020. Thus, this article provides a novel material ZEQ, which is tunable luminescence and ultra-stable. The strategy provides the route that the luminescence of Eu ions and QDs can be observed at the same time, solving the difficulty of the rare earth ions entering into the QDs lattice. Moreover, the ZEQ is expected to be used as the light source for solid-state lighting and also provides valuable research results for future exploration of functional glass containing both rare-earth ions and QDs materials.

Synthesis of metformin-derived fluorescent quantum dots: uptake, cytotoxicity, and inhibition in human breast cancer cells through autophagy pathway

BackgroundBreast cancer remains a challenge for physicians. Metformin, an antidiabetic drug, show promising anticancer properties against cancers. An emerging quantum dot (QD) material improves therapeutic agents’ anticancer and imaging properties. QD are nano-sized particles with extreme application in nanotechnology captured by cells and accumulated inside cells, suggesting bioimaging and effective anticancer outcomes. In this study, a simple one-pot hydrothermal method was used to synthesize fluorescent metformin-derived carbon dots (M-CDs) and then investigated the cytotoxic effects and imaging features on two human breast cancer cell lines including, MCF-7 and MDA-MB-231 cells.ResultsResults showed that M-CDs profoundly decreased the viability of both cancer cells. IC50 values showed that M-CDs were more cytotoxic than metformin either 24–48 h post-treatment. Cancer cells uptake M-CDs successfully, which causes morphological changes in cells and increased levels of intracellular ROS. The number of Oil Red O-positive cells and the expression of caspase-3 protein were increased in M-CDs treated cells. Authophagic factors including, AMPK, mTOR, and P62 were down-regulated, while p-AMPK, Becline-1, LC3 I, and LC3 II were up-regulated in M-CDs treated cells. Finally, M-CDs caused a decrease in the wound healing rate of cells.ConclusionsFor the first, M-CDs were synthesized by simple one-pot hydrothermal treatment without further purification. M-CDs inhibited both breast cancer cells through modulating autophagy signalling.Graphical

Recent Progress of Quantum Dots Light-Emitting Diodes: Materials, Device Structures, and Display Applications.

Colloidal quantum dots (QDs), as a class of 0D semiconductor materials, have generated widespread interest due to their adjustable band gap, exceptional color purity, near-unity quantum yield, and solution-processability. With decades of dedicated research, the potential applications of quantum dots have garnered significant recognition in both the academic and industrial communities. Furthermore, the related quantum dot light-emitting diodes (QLEDs) stand out as one of the most promising contenders for the next-generation display technologies. Although QD-based color conversion films are applied to improve the color gamut of existing display technologies, the broader application of QLED devices remains in its nascent stages, facing many challenges on the path to commercialization. This review encapsulates the historical discovery and subsequent research advancements in QD materials and their synthesis methods. Additionally, the working mechanisms and architectural design of QLED prototype devices are discussed. Furthermore, the review surveys the latest advancements of QLED devices within the display industry. The narrative concludes with an examination of the challenges and perspectives of QLED technology in the foreseeable future.

P‐139: Effect of Surface Ligands on Device Performance for Infrared Light‐Emitting Diodes†

Infrared (IR) emitted Quantum Dots (QDs) are fascinating materials with the unique feature of energy levels engineering based on ligand exchange. In this work, the ligand of QDs is modified to form the charge transport layer of IR light‐emitting diodes (LEDs). The corresponding IRLEDs fabricated with all QDs materials can obtain electroluminescence (EL) peak of 1200 nm, including the wide full width at half maximum (FWHM), and an EQE of 4.5%.

20‐5: Quantum Dots and Device Optimizations towards Ink Jet Printing Quantum Dots Light Emitting Diodes Displays

In this paper, we have meticulously refined both the quantum dot (QD) materials, particularly the blue variants, and the ink formulations to achieve aesthetically pleasing, high‐performance printing devices. Furthermore, in anticipation of future mass production challenges, we have tailored the quantum dot ligands and adopted surface passivation of zinc oxide nanoparticles, leveraging their inherent material properties. This innovation has culminated in remarkable enhancements for inkjet QLED device in long‐term storage stability and efficiency.

36‐4: CQD‐Based Sensors for Large Format SWIR Imaging

Quantum dots have been rapidly developed in the display field, especially as photoluminescent color conversion layers. At the same time, quantum dots have also made increasing research progress in the detection field. We reported a short‐wave infrared sensor based on colloidal quantum dot technology. The photosensitive layer of the sensor uses HgTe colloidal quantum dot material. The detection band is 0.9~1.7um, the resolution is 1280*1024, and the pixel pitch is 15um. Colloidal quantum dot short‐wave infrared sensors get rid of the limitations of the indium pillar flip‐chip bonding process of traditional indium gallium arsenide CMOS short‐wave infrared focal plane sensors. The preparation process is simple, the yield is higher, and the cost is low. Based on the colloidal quantum dot shortwave infrared sensor, we implemented a shortwave infrared camera and characterized its performance parameters, and then we successfully captured shortwave infrared images through the shortwave infrared camera.

Two-photon absorption in quantum dots with Hellmann potential

Abstract We study the nonlinear optical absorption properties of a spherical quantum dot (SQD) with Hellmann potential, focusing on the two-photon absorption (TPA) process, using GaAs/AlGaAs material as an example. The radial Schrödinger equation is solved using the Nikiforov-Uvarov method, while the two-photon absorption coefficient is determined through second-order perturbation theory concerning the electron-photon interaction. Our study shows that the intraband transition has a smaller energy transition than the interband transition, leading to TPA spectra for the intraband transition that is restricted within a smaller energy range and exhibits a higher peak value than those for the interband transition. The peak corresponding to the orbital quantum number of electrons in SQD ℓ = 2 consistently appears to the left of the peak corresponding to ℓ = 1 in both intraband and interband transition cases. Additionally, the dependence of the absorption peak position on the order of transition, n, differs between intra- and inter-band transitions. We also observe blue shift behavior in the TPA spectra as all three parameters, r 0, V 0e , and η, increase. Our investigation has the potential to enable the design of novel photonic devices, ultra-fast optical switches, and highly efficient solar cells through the optimization of quantum dot material properties.

Application of quantum dot light-emitting diode harvest by quantum dot solar cells

Recent progress in photovoltaic (PV) cell usage has been hindered due to a shortage of suitable materials that emit adequate wavelengths of light energy and convert it to electricity. Quantum dot light-emitting diodes (QLEDs) and quantum dot solar cells (QDSCs) have been identified as promising artificial light sources and PV cell types to nicely fit into this solution, not only complying with that but also being controllable, flexible, portable, and lightweight. The purpose of this study is to provide a review of the application of how QLEDs can be collected for QDSCs. First, we introduce QLEDs as artificial light sources, briefly outline their mechanics and benefits, and compare them to other light sources for QDSC harvesting. Then, we summarize the mechanisms that occur when a QDSC absorbs a photon from a QLED, as well as how these energy flow pathways influence artificial light energy harvest. Finally, we explore the optoelectronic properties of lead sulphide (PbS) and lead selenide (PbSe) as appropriate quantum dots (QDs) materials for current applications in QDSC and QLED technologies. We anticipate that the literature will be comprehensive and relevant to the scientific community interested in creating artificial light energy harvesting and thus researching the most recent alternative method of getting healthy energy.

Research Progress of Heavy-Metal-Free Quantum Dot Light-Emitting Diodes.

At present, heavy-metal-free quantum dot light-emitting diodes (QLEDs) have shown great potential as a research hotspot in the field of optoelectronic devices. This article reviews the research on heavy-metal-free quantum dot (QD) materials and light-emitting diode (LED) devices. In the first section, we discussed the hazards of heavy-metal-containing quantum dots (QDs), such as environmental pollution and human health risks. Next, the main representatives of heavy-metal-free QDs were introduced, such as InP, ZnE (E=S, Se and Te), CuInS2, Ag2S, and so on. In the next section, we discussed the synthesis methods of heavy-metal-free QDs, including the hot injection (HI) method, the heat up (HU) method, the cation exchange (CE) method, the successful ionic layer adsorption and reaction (SILAR) method, and so on. Finally, important progress in the development of heavy-metal-free QLEDs was summarized in three aspects (QD emitter layer, hole transport layer, and electron transport layer).

Synthesis of temperature and salt resistance silicon dots for effective enhanced oil recovery in tight reservoir

The intensive development of tight reservoirs has positioned them as a strategic alternative to conventional oil and gas resources. Existing enhanced oil recovery (EOR) methods struggle to effectively exploring reservoir oil, resulting in low recovery rates. Novel and effective means of developing tight reservoirs are urgently needed. Nanomaterials have shown promising applications in improving water flooding efficiency, with in-depth research into mechanisms that lower injection pressure and increase water injection volumes. However, the extent of improvement remains limited. In this study, a silicon quantum dots (Si-QDs) material was synthesized via a hydrothermal synthesis method and used to prepare a nanofluid for the efficient recovery of tight reservoir. The Si-QDs, with an approximate diameter of 3 nm and a spherical structure, were surface functionalized with benzenesulfonic acid groups to enhance the performance. The developed nanofluid demonstrated stability without aggregation at 120 °C and a salinity of 60000 mg/L. Core flooding experiments have demonstrated the attractive EOR capabilities of Si-QDs, shedding light of the EOR mechanisms. Si-QDs effectively improve the wettability of rocks, enhancing the sweeping coefficient of injected fluids and expanding sweeping area. Within this sweeping region, Si-QDs efficiently stripping adsorbed oil from the matrix, thus increasing sweeping efficiency. Furthermore, Si-QDs could modify the state of pore-confined crude oil, breaking it down into smaller particles that are easier to displacement in subsequent stages. Si-QDs exhibit compelling EOR potential, positioning them as a promising approach for effectively developing tight oil reservoirs.

Efficient green light-emitting diodes based on alloy quantum dots with an organic/inorganic hybrid surface passivation

As we know, the ligands on the surface of core/shell structured quantum dots (QDs) play an important role. They not only bind with metal ions to passivate surface defects but also have a great influence on colloidal stability. All-organic or all-inorganic ligands afford QDs with some disadvantages such as low conductivity, poor dispersibility and undesirable stability. By combining with the advantages of organic and inorganic ligands, herein, we achieve an organic/inorganic hybrid surface passivation through exchanging partial oleic acid ligands with chlorine ions (Cl−), affording QD with a core/shell structure of CdZnSe/ZnSe/ZnS/OACl. It exhibits an excellent nanostructure with a mean size of around 11.6 nm. According to X-ray photoelectron spectroscopy (XPS) spectra, around 30% oleid acid ligands are removed by Cl−, resulting in the hybrid surface passivation. The CdZnSe/ZnSe/ZnS/OACl QD exhibit an efficient green emission at the wavelength of around 535 nm with a quantum yield of over 90%. The QD light-emitting diode (QLED) based on CdZnSe/ZnSe/ZnS/OACl exhibits a peak EQE of 15.6% and a brightness of over 1.1 × 105 cd m−2 at 6 V, corresponding to an efficient green emitting device. Therefore, we believe that the hybrid surface passivation could provid a reliable avenue to efficient QD materials.

Highly luminescent and stable MAPbBr3 quantum dot fabrication via a hybrid capping ligand

Perovskite quantum dots (PEQDs) are next-generation quantum dot materials that have attracted attention in various areas such as display, radiation scintillator, and photodetector. However, PEQD defects that occur for various reasons hinder the commercialization of PEQDs. Herein, we reported a new strategy for a hybrid ligand comprising 1-octanethiol (OT) and octylammonium bromide that can passivate the defects of PEQD and effectively reduce the Stokes shift. First, the increase in the OT concentration in hybrid ligands leads to an increase in the PEQD size and a decrease in the Stokes shift. Second, OT in hybrid ligands can stabilize the PEQD solution by binding to an MA ion, which is easily degraded by atmospheric oxygen, thereby suppressing the generation of metallic Pb that serves as a defect in PEQDs. Consequently, PEQDs by hybrid ligands reduced the defects, particularly metallic Pb, leading to strong green emission with low Stokes shift with a photoluminescence quantum yield of 99.3 % and high stability under atmospheric conditions.

PbS quantum dot thin film dry etching

Many consumer products used daily contain sensors and image sensors (smartphones, cars, automated tools, etc.). There is a growing demand to enhance the capabilities of industrial products to probe their environment more efficiently, i.e., under difficult conditions (smoke, darkness, etc.). One solution is to extend the capabilities of image sensors to detect light toward the near-infrared and short-wave infrared (SWIR) regions. Because silicon has weak absorption properties in the infrared, especially in the SWIR region, manufacturers are investigating the use of new materials to build these sensors. To this end, colloidal quantum dot (QD) thin films made from the assembly of PbS nanoparticles have emerged as promising materials. They offer tunable bandgaps, favorable absorption properties, and scalability in production. However, patterning the active parts of photodiodes by plasma etching of this new material presents challenges. The etching chemistry must be selected to volatilize Pb and S without modifying the unetched active part of the PbS QD photodiode, and the etching profile should be anisotropic. In this study, we have screened several plasma operating conditions (power, pressure, and temperature) in various chemistries (H2, Cl2, HBr, and N2). To understand the etch mechanisms and profiles, ToF-SIMS and TEM/energy dispersive x-ray were employed. Our findings reveal that halogen-based plasmas cause QD material deterioration through Cl or Br diffusion deep in the film. While H2 plasmas are efficient to etch PbS QD films, they result in high roughness due to the removal of the carbonated ligands that separate PbS QDs. This ligand etching is followed by QD coalescence leading to significant roughness. However, the addition of N2 to H2 can prevent this phenomenon by forming a diffusion barrier at the surface, resulting in favorable etching characteristics.

Preface

Preface Third International Conference on Physics of Materials & Nanotechnology (ICPN-2023) On behalf of Organizing committee, it’s my great pleasure to bring this beautiful collection of research articles which were presented in the Third International Conference on Physics of Materials and Nanotechnology (ICPN-2023) which was organized by Department of Physics, Mangalore University, Mangalagangothri, Mangalore (Karnataka), India during September 21st to 23rd, 2023. This conference will serve as an ideal platform for young researchers, academician and students from all over the country as well as from the globe to share their ideas and experiences in Physics, Nanotechnology and Nano science research. This conference provided meaningful platform for young researchers to update and upgrade themselves. The main themes of the conferences Advanced Energy and Solar Materials, 1-D, 2-D and Quantum dot Materials, Advanced Electronic Materials, Polymers, Conducting Polymer and Thin films, Solid State Materials and their properties, Sensors and actuators, Carbon related materials, Metal Oxide & Sulphide Materials, Ferroelectrics and dielectric materials, Soft, Magnetic and smart materials, Nano Material, Nanotechnology, Chemistry of Materials, Alloys, Semiconductor and optical Materials and Crystal growth & applications etc. I am glad that experts in the various field of Nanotechnology are here to present and discussed their ideas and latest development in the field. ICPN 2023 has received a great response throughout the country and globe. It includes 14 invited talks, 11 oral presentations and more than 120 poster presentations. We have received more than 130 papers for the publications in this issue, after reviewing and editing processes, 47 papers were accepted for the publication out of 74 submitted papers. We thank the authors for their contribution and the reviewers for their comments to improve the quality of article. I would like to express my gratitude to all members of organizing committee, staff, research scholars and postgraduate students of the institute for their willingness, commitment, dedication and relentless efforts in ensuring that conference was successful.List of Editorial Board is available in this pdf.