1
|
Tran MT, Quang Trung D, Tri Tuan N, Tuan NT, Tu N, Van Du N, Duy Hung N, Van Quang N, Thi Hao Tam T, Trung Kien ND, Hieu NM, Huy PT. Highly efficient green-emitting ZnO:Cu 2+ phosphors for NUV-pumped white-emitting diodes. Dalton Trans 2023; 52:12704-12716. [PMID: 37609935 DOI: 10.1039/d3dt01663c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
Phosphor-converted white light-emitting diodes (WLEDs) have received significant attention; however, the leaked light from their blue InGaN chips has an undesirable effect on human health. Hence, it is necessary to develop red, green, and blue-emitting phosphors, which can be excited by an NUV chip instead of a blue chip. Herein, green-emitting ZnO:Cu2+ phosphors have been successfully synthesized by a simple and facile thermal diffusion method. The obtained powder shows a broad emission band peaking at 525 nm and a strong absorption peak at 377 nm. The ZnO:5%Cu2+ phosphor annealed at 800 °C in 2 hours revealed a lifetime of 0.57 ms, an activation energy of 0.212 eV, and the highest emission intensity with (x, y) CIE colour coordinates (0.3130, 0.5253). A WLED prototype has been fabricated by coating the ZnO:5%Cu2+ phosphor on an NUV 375 nm LED chip, where this coated phosphor shows a high quantum efficiency (QE) of 56.6%. This is, so far, the highest reported QE value for ZnO-based phosphors. These results suggest that the ZnO:Cu2+ phosphor could be an excellent candidate for NUV-pumped phosphor-converted WLED applications.
Collapse
Affiliation(s)
- Manh Trung Tran
- Faculty of Materials Science and Engineering, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam.
| | - Do Quang Trung
- Faculty of Materials Science and Engineering, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam.
- Faculty of Fundamental Sciences, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam
| | - Nguyen Tri Tuan
- College of Natural Science, Can Tho University, Ninh-Kieu District, Can Tho 94000, Vietnam
| | - Nguyen Trong Tuan
- College of Natural Science, Can Tho University, Ninh-Kieu District, Can Tho 94000, Vietnam
| | - Nguyen Tu
- Faculty of Materials Science and Engineering, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam.
- Faculty of Fundamental Sciences, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam
| | - Nguyen Van Du
- Faculty of Materials Science and Engineering, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam.
- Faculty of Fundamental Sciences, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam
| | - Nguyen Duy Hung
- International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, 01 Dai Co Viet Street, Hanoi 10000, Vietnam
| | - Nguyen Van Quang
- Department of Chemistry, Hanoi Pedagogical University 2, Phuc Yen, Vinh Phuc, Vietnam
| | - Tong Thi Hao Tam
- School of Information Technology and Digital Economics, National Economic University, 207 Giai Phong Street, Hanoi 10000, Vietnam
| | - Nguyen Duc Trung Kien
- Faculty of Electrical and Electronic Engineering, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam
| | - Nguyen Minh Hieu
- Faculty of Materials Science and Engineering, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam.
| | - Pham Thanh Huy
- Faculty of Materials Science and Engineering, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam.
| |
Collapse
|
2
|
Xue S, Chen G, Zhang J, Che R. Insight into Surface Electronic Effects on Pd Nanostructures as Efficient Electrocatalysts. NANO LETTERS 2023; 23:2778-2785. [PMID: 37010265 DOI: 10.1021/acs.nanolett.3c00056] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Although the unique properties of nanomaterials have endowed enzyme-mimic catalysts with broad applications, the development of catalysts still relies on trial-and-error strategies without predictive indicators. Surface electronic structures have rarely been studied in enzyme-mimic catalysts. Herein, we present a platform for understanding the impact of surface electronic structures on electrocatalysis toward H2O2 decomposition, using the Pd icosahedra (Pd ico), Pd octahedra (Pd oct) and Pd cubic nanocrystals as electrocatalysts. The electronic properties on Pd were modulated with a correlation of surface orientation. We revealed the relationship between the electronic properties and electrocatalytic performance, in which the surface electron accumulation can boost the electrocatalytic activity of the enzyme-mimic catalysts. As a result, the Pd icodimer exhibits the highest electrocatalytic and sensing efficiency. This work offers new perspectives for the investigation of structure-activity relationships and provides an effective knob for utilizing the surface electronic structures to boost the catalytic performance for enzyme-mimics.
Collapse
Affiliation(s)
- Shuyan Xue
- Laboratory of Advanced Materials, Shanghai Key Lab of Molecular Catalysis and Innovative Materials, Academy for Engineering & Technology, Fudan University, Shanghai 200438, P. R. China
| | - Guanyu Chen
- Laboratory of Advanced Materials, Shanghai Key Lab of Molecular Catalysis and Innovative Materials, Academy for Engineering & Technology, Fudan University, Shanghai 200438, P. R. China
| | | | - Renchao Che
- Laboratory of Advanced Materials, Shanghai Key Lab of Molecular Catalysis and Innovative Materials, Academy for Engineering & Technology, Fudan University, Shanghai 200438, P. R. China
- Zhejiang Laboratory, Hangzhou 311100, China
| |
Collapse
|
3
|
Chakraborty S, Grandhi GK, Viswanatha R. Study of the Interface and Radial Dopant Position in Semiconductor Heterostructures Using X-ray Absorption Spectroscopy. J Phys Chem Lett 2022; 13:11036-11043. [PMID: 36413658 DOI: 10.1021/acs.jpclett.2c02704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Two questions that remain a challenge in the field of colloidal doped core/shell nanomaterials of different morphologies are the nature of the interface and the radial location of the dopant ion due to the diffusion within the lattice. Using a model system of Cu-doped CdSe/CdS quantum dots, we develop an in-depth understanding of the extended X-ray absorption fine structure (EXAFS) spectra of the dopant and host atoms to address both issues. Our findings suggest that the interface is not sharp, in agreement with the nonstructural studies in the literature. Local structure analysis around the Cu dopant ion confirms that Cu drifts out from the core toward the outer region in the absence of the shell but stays mostly in the core after the formation of a sufficiently thick interfacial barrier (∼2 monolayers). This study highlights the significance of EXAFS spectroscopy in understanding the nature of the interface in nanomaterials.
Collapse
|
4
|
Mondal P, Viswanatha R. Insights into the Oxidation State of Cu Dopants in II-VI Semiconductor Nanocrystals. J Phys Chem Lett 2022; 13:1952-1961. [PMID: 35188398 DOI: 10.1021/acs.jpclett.1c04076] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Luminescent Cu-doped semiconductor nanocrystals have played a pivotal role in the emergence of lighting and display applications for a long time. However, consensus regarding the Cu oxidation state and hence their emission mechanism has not been attained. Distinction between seemingly simple optically and magnetically active Cu2+ and inactive Cu1+ has surprisingly been the subject matter of debate in the literature for more than a decade. In this Perspective, we first discuss the fundamental quantum mechanical phenomenon explaining the optical properties of the monovalent and divalent Cu dopants. We then focus down on various techniques used to differentiate between these two fundamental mechanisms, their benefits, and their pitfalls arising in large part because of the lack of spatial separation. Hence, to obtain a cohesive story consistent with all the observations, we discuss recent results from single-molecule spectroscopy to understand the optical properties and hence the oxidation state of internally doped Cu in doped nanocrystals.
Collapse
|
5
|
Nishimura H, Enomoto K, Pu YJ, Kim D. Hydrothermal synthesis of water-soluble Mn- and Cu-doped CdSe quantum dots with multi-shell structures and their photoluminescence properties. RSC Adv 2022; 12:6255-6264. [PMID: 35424533 PMCID: PMC8982036 DOI: 10.1039/d1ra08491g] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Accepted: 02/16/2022] [Indexed: 12/03/2022] Open
Abstract
Optical properties of semiconductor quantum dots (QDs) can be tuned by doping with transition metal ions. In this study, water-soluble CdSe/ZnS:Mn/ZnS QDs with the core/shell/shell structure were synthesized through a hydrothermal method, in which the surface of the CdSe core was coated with a ZnS:Mn shell and ZnS capping shell. Herein, the CdSe core QDs were prepared first and then doped with Mn2+; therefore, the QD size and doping level could be controlled independently and interference from the self-purifying effect could be avoided. When CdSe cores with diameters less than 1.9 nm were used, Mn-related photoluminescence (PL) was observed as the main PL band, whereas the band-edge PL was mainly observed when larger CdSe cores were used. Furthermore, using ZnS:Cu as the doping shell layer, CdSe/ZnS:Cu/ZnS and ZnSe/ZnS:Cu/ZnS nanoparticles were successfully synthesized, and Cu-related PL was clearly observed. These results indicate that the core/shell/shell QD structure with doping in the shell layer is a versatile method for synthesizing doped QDs.
Collapse
Affiliation(s)
- Hisaaki Nishimura
- Department of Applied Physics, Osaka City University Osaka 558-8585 Japan
| | - Kazushi Enomoto
- RIKEN Center for Emergent Matter Science (CEMS) Saitama 351-0198 Japan
| | - Yong-Jin Pu
- RIKEN Center for Emergent Matter Science (CEMS) Saitama 351-0198 Japan
| | - DaeGwi Kim
- Department of Applied Physics, Osaka City University Osaka 558-8585 Japan
| |
Collapse
|
6
|
Wu R, Bai Z, Jiang J, Yao H, Qin S. Research on the photoluminescence properties of Cu 2+-doped perovskite CsPbCl 3 quantum dots. RSC Adv 2021; 11:8430-8436. [PMID: 35423370 PMCID: PMC8695195 DOI: 10.1039/d0ra09043c] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 01/12/2021] [Indexed: 12/19/2022] Open
Abstract
CsPbX3 (X = Cl, Br, and I) quantum dots (QDs) and Cu2+-doped CsPbCl3 QDs with different Cu-to-Pb molar ratios were synthesized via a solvent-based thermal synthesis method. The photoluminescence (PL) properties of these Cu2+-doped CsPbCl3 QDs were also investigated in this study. The results showed that with the increase in the Cl− concentration the surface defects of CsPb(Cl/Br)3 QDs increased, which resulted in an increase in the non-radiative recombination of excitons and weakened the PL intensity. Moreover, Cu2+-doped CsPbCl3 QDs maintained the cubic crystal structure of the initial phases. Owing to the doping of Cu2+ ions, the surface defects of CsPbCl3 QDs were effectively eliminated, which facilitated the excitonic recombination via a radiative pathway. The PL quantum yields (PLQYs) of Cu2+-doped CsPbCl3 QDs were increased to 51%, showing great photostability. From the results, it is believed that Cu:CsPbCl3 QDs can be widely used in optoelectronic devices. Schematic of the synthesis of Cu:CsPbCl3 QDs and PL spectra.![]()
Collapse
Affiliation(s)
- Ronghua Wu
- Guizhou Province Key Lab. for Photoelectric Technology and Application, Guizhou University Guiyang City 550025 People's Republic of China
| | - Zhongchen Bai
- Guizhou Province Key Lab. for Photoelectric Technology and Application, Guizhou University Guiyang City 550025 People's Republic of China.,College of Medicine, Guizhou University Guiyang City 550025 People's Republic of China
| | - Jinguo Jiang
- Guizhou Province Key Lab. for Photoelectric Technology and Application, Guizhou University Guiyang City 550025 People's Republic of China
| | - Heng Yao
- Guizhou Province Key Lab. for Photoelectric Technology and Application, Guizhou University Guiyang City 550025 People's Republic of China
| | - Shuijie Qin
- Guizhou Province Key Lab. for Photoelectric Technology and Application, Guizhou University Guiyang City 550025 People's Republic of China
| |
Collapse
|
7
|
Bhattacharyya B, Mukherjee A, Mahadevu R, Pandey A. Tuning radiative lifetimes in semiconductor quantum dots. J Chem Phys 2021; 154:074707. [PMID: 33607898 DOI: 10.1063/5.0036676] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Photonic devices stand to benefit from the development of chromophores with tunable, precisely controlled spontaneous emission lifetimes. Here, we demonstrate a method to continuously tune the radiative emission lifetimes of a class of chromophores by varying the density of electronic states involved in the emission process. In particular, we examined the peculiar composition-dependent electronic structure of copper doped CdZnSe quantum dots. It is shown that the nature and density of electronic states involved with the emission process is a function of copper inclusion level, providing a very direct handle for controlling the spontaneous lifetimes. The spontaneous emission lifetimes are estimated by examining the ratios of emission lifetimes to absolute quantum yields and also measured directly by ultrafast luminescence upconversion experiments. We find excellent agreement between these classes of experiments. This scheme enables us to tune spontaneous emission lifetimes by three orders of magnitude from ∼15 ns to over ∼7 µs, which is unprecedented in existing lumophores.
Collapse
Affiliation(s)
- Biswajit Bhattacharyya
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India
| | - Arpita Mukherjee
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India
| | - Rekha Mahadevu
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India
| | - Anshu Pandey
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India
| |
Collapse
|
8
|
Mondal P, Chakraborty S, Grandhi GK, Viswanatha R. Copper Doping in II-VI Semiconductor Nanocrystals: Single-Particle Fluorescence Study. J Phys Chem Lett 2020; 11:5367-5372. [PMID: 32522003 DOI: 10.1021/acs.jpclett.0c01570] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Copper doping in II-VI semiconductor nanocrystals (NCs) has sparked enormous debate regarding the oxidation state of Cu ions and their hugely differing consequences in optoelectronic applications. The identity of a magnetically active Cu2+ ion or a magnetically inactive d10 Cu+ ion has generally been probed using optical techniques, and confusion arises from the spatial clutter that is part of the technique. One major probe that could declutter the data obtained from ensemble emission is single-particle fluorescence spectroscopy. In this work, using this very technique along with X-ray absorption spectroscopy probing the local environment of dopant ions, we study Cu-doped II-VI semiconductor NCs to find conclusive evidence on the oxidation state of Cu dopants and hence the mechanism of their emission. Detailed analysis of blinking properties has been used to study the single-particle nature of the NCs.
Collapse
|
9
|
Ca NX, Van HT, Do PV, Thanh LD, Tan PM, Truong NX, Oanh VTK, Binh NT, Hien NT. Influence of precursor ratio and dopant concentration on the structure and optical properties of Cu-doped ZnCdSe-alloyed quantum dots. RSC Adv 2020; 10:25618-25628. [PMID: 35518601 PMCID: PMC9055275 DOI: 10.1039/d0ra04257a] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 06/22/2020] [Indexed: 11/21/2022] Open
Abstract
Tunable copper doped Zn1−xCdxS alloy quantum dots (QDs) were successfully synthesized by the wet chemical method.
Collapse
Affiliation(s)
- N. X. Ca
- Department of Physics and Technology
- TNU—University of Sciences
- Thai Nguyen
- Vietnam
| | - H. T. Van
- Institute of Research and Development
- Duy Tan University
- Da Nang
- Vietnam
| | | | | | - P. M. Tan
- Faculty of Fundamental Sciences
- Thai Nguyen University of Technology
- Thai Nguyen
- Vietnam
| | - N. X. Truong
- Institute of Materials Science
- Vietnam Academy of Science and Technology
- Ha Noi
- Vietnam
| | - V. T. K. Oanh
- Institute of Materials Science
- Vietnam Academy of Science and Technology
- Ha Noi
- Vietnam
| | - N. T. Binh
- Institute of Physics
- Vietnam Academy of Science and Technology
- Hanoi
- Vietnam
| | - N. T. Hien
- Ceramics and Biomaterials Research Group
- Advanced Institute of Materials Science
- Ton Duc Thang University
- Ho Chi Minh City
- Vietnam
| |
Collapse
|
10
|
Observation of a phonon bottleneck in copper-doped colloidal quantum dots. Nat Commun 2019; 10:4532. [PMID: 31586066 PMCID: PMC6778069 DOI: 10.1038/s41467-019-12558-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Accepted: 09/18/2019] [Indexed: 11/09/2022] Open
Abstract
Hot electrons can dramatically improve the efficiency of solar cells and sensitize energetically-demanding photochemical reactions. Efficient hot electron devices have been hindered by sub-picosecond intraband cooling of hot electrons in typical semiconductors via electron-phonon scattering. Semiconductor quantum dots were predicted to exhibit a “phonon bottleneck” for hot electron relaxation as their quantum-confined electrons would couple very inefficiently to phonons. However, typical cadmium selenide dots still exhibit sub-picosecond hot electron cooling, bypassing the phonon bottleneck possibly via an Auger-like process whereby the excessive energy of the hot electron is transferred to the hole. Here we demonstrate this cooling mechanism can be suppressed in copper-doped cadmium selenide colloidal quantum dots due to femtosecond hole capturing by copper-dopants. As a result, we observe a lifetime of ~8.6 picosecond for 1Pe hot electrons which is more than 30-fold longer than that in same-sized, undoped dots (~0.25 picosecond). Weak electron-phonon scattering that can enable long-lived hot electrons in semiconductors is of interest in hot carrier solar cells. Here, the authors report copper-doped colloidal cadmium-selenide quantum dots with hot electron lifetime extended by more than 30-fold compared to undoped dots.
Collapse
|
11
|
Li C, Wu P. Cu-doped quantum dots: a new class of near-infrared emitting fluorophores for bioanalysis and bioimaging. LUMINESCENCE 2019; 34:782-789. [PMID: 31297953 DOI: 10.1002/bio.3679] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Revised: 06/07/2019] [Accepted: 06/13/2019] [Indexed: 01/25/2023]
Abstract
Transition metal ion-doped quantum dots (QDs) exhibit unique optical and photophysical properties that offer significant advantages over undoped QDs, such as larger Stokes shift to avoid self-absorption/energy transfer, longer excited-state lifetimes, wider spectral window, and improved chemical and thermal stability. Among the doped QDs emitters, Cu is widely introduced into the doped QDs as novel, efficient, stable, and tunable optical materials that span a wide spectrum from blue to near-infrared (NIR) light. Their unique physical and chemical characteristics enable the use of Cu-doped QDs as NIR labels for bioanalysis and bioimaging. In this review, we discuss doping mechanisms and optical properties of Cu-doped QDs that are capable of NIR emission. Applications of Cu-doped QDs in in vitro biosensing and in in vivo bioimaging are highlighted. Moreover, a prospect of the future of Cu-doped QDs for bioanalysis and bioimaging are also summarized.
Collapse
Affiliation(s)
- Chenghui Li
- Analytical & Testing Centre, Sichuan University, Chengdu, China
| | - Peng Wu
- Analytical & Testing Centre, Sichuan University, Chengdu, China
| |
Collapse
|
12
|
Makkar M, Saha A, Khalid S, Viswanatha R. Thermodynamics of Dual Doping in Quantum Dots. J Phys Chem Lett 2019; 10:1992-1998. [PMID: 30945549 DOI: 10.1021/acs.jpclett.9b00606] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Dual doping is a powerful way to tailor the properties of semiconductor quantum dots (QDs) arising out of host-dopant and dopant-dopant interactions. Nevertheless, it has seldom been explored due to a variety of thermodynamic challenges, such as the differential bonding strength and diffusion constant within the host matrix that integrates with the host in dissimilar ways. This work discusses the challenges involved in administering them within the constraints of one host under similar conditions of temperature, time, and chemical parameters such as solubility and reactivity using CoPt-doped CdS QDs as a model system. In addition, the various forces in play, such as Kirkendall diffusion, solid- and liquid-state diffusion, hard acid soft base interaction with the host, and the effect of lattice strain due to lattice mismatch, are studied to understand the feasibility of the core to doped transformation. These findings suggest a potential approach for manipulating the properties of semiconductors by dual doping engineering.
Collapse
Affiliation(s)
| | | | - Syed Khalid
- Brookhaven National Laboratory , Upton , New York 11973-5000 , United States
| | | |
Collapse
|
13
|
Kaur M, Sharma A, Olutas M, Erdem O, Kumar A, Sharma M, Demir HV. Cd-free Cu-doped ZnInS/ZnS Core/Shell Nanocrystals: Controlled Synthesis And Photophysical Properties. NANOSCALE RESEARCH LETTERS 2018; 13:182. [PMID: 29916083 PMCID: PMC6006007 DOI: 10.1186/s11671-018-2599-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Accepted: 06/11/2018] [Indexed: 06/08/2023]
Abstract
Here, we report efficient composition-tunable Cu-doped ZnInS/ZnS (core and core/shell) colloidal nanocrystals (CNCs) synthesized by using a colloidal non-injection method. The initial precursors for the synthesis were used in oleate form rather than in powder form, resulting in a nearly defect-free photoluminescence (PL) emission. The change in Zn/In ratio tunes the percentage incorporation of Cu in CNCs. These highly monodisperse Cu-doped ZnInS CNCs having variable Zn/In ratios possess peak emission wavelength tunable from 550 to 650 nm in the visible spectrum. The quantum yield (QY) of these synthesized Cd-free CNCs increases from 6.0 to 65.0% after coating with a ZnS shell. The CNCs possessing emission from a mixed contribution of deep trap and dopant states to only dominant dopant-related Stokes-shifted emission are realized by a careful control of stoichiometric ratio of different reactant precursors during synthesis. The origin of this shift in emission was understood by using steady state and time-resolved fluorescence (TRF) spectroscopy studies. As a proof-of-concept demonstration, these blue excitable Cu-doped ZnInS/ZnS CNCs have been integrated with commercial blue LEDs to generate white-light emission (WLE). The suitable combination of these highly efficient doped CNCs results led to a Commission Internationale de l'Enclairage (CIE) color coordinates of (0.33, 0.31) at a color coordinate temperature (CCT) of 3694 K, with a luminous efficacy of optical radiation (LER) of 170 lm/Wopt and a color rendering index (CRI) of 88.
Collapse
Affiliation(s)
- Manpreet Kaur
- Department of Nanotechnology, Sri Guru Granth Sahib World University, Punjab, 140406 India
- Department of Electrical and Electronics Engineering, Department of Physics, and UNAM–Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara, Turkey
| | - Ashma Sharma
- Department of Electrical and Electronics Engineering, Department of Physics, and UNAM–Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara, Turkey
- LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronics Engineering, School of Physical and Mathematical Sciences, School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore, 639798 Singapore
| | - Murat Olutas
- Department of Electrical and Electronics Engineering, Department of Physics, and UNAM–Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara, Turkey
- Department of Physics, Abant Izzet Baysal University, 14030 Bolu, Turkey
| | - Onur Erdem
- Department of Electrical and Electronics Engineering, Department of Physics, and UNAM–Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara, Turkey
| | - Akshay Kumar
- Department of Nanotechnology, Sri Guru Granth Sahib World University, Punjab, 140406 India
| | - Manoj Sharma
- Department of Nanotechnology, Sri Guru Granth Sahib World University, Punjab, 140406 India
- Department of Electrical and Electronics Engineering, Department of Physics, and UNAM–Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara, Turkey
- LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronics Engineering, School of Physical and Mathematical Sciences, School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore, 639798 Singapore
| | - Hilmi Volkan Demir
- Department of Electrical and Electronics Engineering, Department of Physics, and UNAM–Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara, Turkey
- LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronics Engineering, School of Physical and Mathematical Sciences, School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore, 639798 Singapore
| |
Collapse
|
14
|
Mahadevu R, Pandey A. Thermodynamic Model for Quantum Dot Assemblies Formed Because of Charge Transfer. ACS OMEGA 2018; 3:266-272. [PMID: 31457892 PMCID: PMC6641234 DOI: 10.1021/acsomega.7b01486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 12/25/2017] [Indexed: 06/10/2023]
Abstract
Two initially neutral semiconductor quantum dots with appropriate band offsets can participate in a ground state charge transfer process. The charge transfer manifests itself in the form of bleaching of optical transitions and also causes the quantum dots to precipitate from solution, giving rise to assemblies with unusual properties. As this represents a postsynthetic modification of the electronic structure of quantum dots, it holds tremendous potential for improving the characteristics of quantum dot devices. Here, we study the dependencies of the properties of these assemblies on the structure of the participating quantum dots. In particular, we find that for assemblies formed out of Cu:CdS and ZnTe/CdS quantum dots, the composition of the assembly varies from 1:1.26 to 1:0.23 ZnTe/CdS to Cu:CdS as the shell thickness of CdS in ZnTe/CdS is increased. In contrast, the composition changes from 1:1.1 to 1:15 for PbSe/CdSe and Cu:CdS quantum dots, as the size of the PbSe core is increased. These observations are explained on the basis of a phenomenological thermodynamic model. The applicability of thermodynamics to this example of self-assembly is verified empirically.
Collapse
|
15
|
Hughes KE, Hartstein KH, Gamelin DR. Photodoping and Transient Spectroscopies of Copper-Doped CdSe/CdS Nanocrystals. ACS NANO 2018; 12:718-728. [PMID: 29286633 DOI: 10.1021/acsnano.7b07879] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
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 (MLCBCT) absorption band and also reveal a photoinduced midgap valence-band (VB)-to-copper charge-transfer (LVBMCT) 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 MLCBCT 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.
Collapse
Affiliation(s)
- Kira E Hughes
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
| | - Kimberly H Hartstein
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
| | - Daniel R Gamelin
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
| |
Collapse
|
16
|
Choi D, Pyo JY, Jang DJ. Impurity Location-Dependent Relaxation Dynamics of Cu:CdS Quantum Dots. NANOSCALE RESEARCH LETTERS 2017; 12:49. [PMID: 28101854 PMCID: PMC5241571 DOI: 10.1186/s11671-017-1832-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 01/03/2017] [Indexed: 06/06/2023]
Abstract
Various types of 2% Cu-incorporated CdS (Cu:CdS) quantum dots (QDs) with very similar sizes have been prepared via a water soluble colloidal method. The locations of Cu impurities in CdS host nanocrystals have been controlled by adopting three different synthetic ways of doping, exchange, and adsorption to understand the impurity location-dependent relaxation dynamics of charge carriers. The oxidation state of incorporated Cu impurities has been found to be +1 and the band-gap energy of Cu:CdS QDs decreases as Cu2S forms at the surfaces of CdS QDs. Broad and red-shifted emission with a large Stokes shift has been observed for Cu:CdS QDs as newly produced Cu-related defects become luminescent centers. The energetically favored hole trapping of thiol molecules, as well as the local environment, inhibits the radiative recombination processes of Cu:CdS QDs, thus resulting in low photoluminescence. Upon excitation, an electron is promoted to the conduction band, leaving a hole on the valence band. The hole is transferred to the Cu+ d-state, changing Cu+ into Cu2+, which then participates in radiative recombination with an electron. Electrons in the conduction band are ensnared into shallow-trap sites within 52 ns. The electrons can be further captured on the time scale of 260 ns into deep-trap sites, where electrons recombine with holes in 820 ns. Our in-depth analysis of carrier relaxation has shown that the possibilities of both nonradiative recombination and energy transfer to Cu impurities become high when Cu ions are located at the surface of CdS QDs.
Collapse
Affiliation(s)
- Dayeon Choi
- Department of Chemistry, Seoul National University, NS60, Seoul, 08826 Republic of Korea
| | - Ji-Young Pyo
- Department of Chemistry, Seoul National University, NS60, Seoul, 08826 Republic of Korea
| | - Du-Jeon Jang
- Department of Chemistry, Seoul National University, NS60, Seoul, 08826 Republic of Korea
| |
Collapse
|
17
|
Pinchetti V, Lorenzon M, McDaniel H, Lorenzi R, Meinardi F, Klimov VI, Brovelli S. Spectro-electrochemical Probing of Intrinsic and Extrinsic Processes in Exciton Recombination in I-III-VI 2 Nanocrystals. NANO LETTERS 2017; 17:4508-4517. [PMID: 28613906 DOI: 10.1021/acs.nanolett.7b02040] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Ternary CuInS2 nanocrystals (CIS NCs) are attracting attention as nontoxic alternatives to heavy metal-based chalcogenides for many technologically relevant applications. The photophysical processes underlying their emission mechanism are, however, still under debate. Here we address this problem by applying, for the first time, spectro-electrochemical methods to core-only CIS and core/shell CIS/ZnS NCs. The application of an electrochemical potential enables us to reversibly tune the NC Fermi energy and thereby control the occupancy of intragap defects involved in exciton decay. The results indicate that, in analogy to copper-doped II-VI NCs, emission occurs via radiative capture of a conduction-band electron by a hole localized on an intragap state likely associated with a Cu-related defect. We observe the increase in the emission efficiency under reductive electrochemical potential, which corresponds to raising the Fermi level, leading to progressive filling of intragap states with electrons. This indicates that the factor limiting the emission efficiency in these NCs is nonradiative electron trapping, while hole trapping is of lesser importance. This observation also suggests that the centers for radiative recombination are Cu2+ defects (preexisting and/or accumulated as a result of photoconversion of Cu1+ ions) as these species contain a pre-existing hole without the need for capturing a valence-band hole generated by photoexcitation. Temperature-controlled photoluminescence experiments indicate that the intrinsic limit on the emission efficiency is imposed by multiphonon nonradiative recombination of a band-edge electron and a localized hole. This process affects both shelled and unshelled CIS NCs to a similar degree, and it can be suppressed by cooling samples to below 100 K. Finally, using experimentally measured decay rates, we formulate a model that describes the electrochemical modulation of the PL efficiency in terms of the availability of intragap electron traps as well as direct injection of electrons into the NC conduction band, which activates nonradiative Auger recombination, or electrochemical conversion of the Cu2+ states into the Cu1+ species that are less emissive due to the need for their "activation" by the capture of photogenerated holes.
Collapse
Affiliation(s)
- Valerio Pinchetti
- Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca , via R. Cozzi 55, I-20125 Milano, Italy
| | - Monica Lorenzon
- Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca , via R. Cozzi 55, I-20125 Milano, Italy
| | - Hunter McDaniel
- UbiQD, Los Alamos, New Mexico 87544, United States
- Chemistry Division and Center for Advanced Solar Photophysics, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
| | - Roberto Lorenzi
- Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca , via R. Cozzi 55, I-20125 Milano, Italy
| | - Francesco Meinardi
- Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca , via R. Cozzi 55, I-20125 Milano, Italy
| | - Victor I Klimov
- Chemistry Division and Center for Advanced Solar Photophysics, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
| | - Sergio Brovelli
- Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca , via R. Cozzi 55, I-20125 Milano, Italy
| |
Collapse
|
18
|
Grandhi GK, Viswanatha R. Demystifying Complex Quantum Dot Heterostructures Using Photogenerated Charge Carriers. J Phys Chem Lett 2017; 8:2043-2048. [PMID: 28430452 DOI: 10.1021/acs.jpclett.7b00534] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The success of heterostructure quantum dots in optoelectronic and photovoltaic applications is based on our understanding of photogenerated charge carrier localization. However, often the actual location of charge carriers in heterostructure semiconductors is quite different from their predicted positions leading to suboptimal results. In this work, photoluminescence of Cu doped heterostructures has been used to study the charge localization of alloys, inverse type I, type II, and quasi type II core/shell structures and graded alloys. Specifically, the adeptness of this method has been assessed over a range of widely studied heterostructures like CdSe/CdS, CdS/CdSe, CdSe/CdTe, Zn1-xCdxSe and Zn1-xCdxS quantum dots systems by doping them with a small percentage of Cu. The electron and hole localization obtained from this method concurs with the pre-existing understanding in cases that have been explored before, while the internal structure of previously unknown heterostructures have been predicted.
Collapse
Affiliation(s)
- G Krishnamurthy Grandhi
- New Chemistry Unit and ‡International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bangalore-560064, India
| | - Ranjani Viswanatha
- New Chemistry Unit and ‡International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bangalore-560064, India
| |
Collapse
|
19
|
|
20
|
Knowles KE, Hartstein KH, Kilburn TB, Marchioro A, Nelson HD, Whitham PJ, Gamelin DR. Luminescent Colloidal Semiconductor Nanocrystals Containing Copper: Synthesis, Photophysics, and Applications. Chem Rev 2016; 116:10820-51. [DOI: 10.1021/acs.chemrev.6b00048] [Citation(s) in RCA: 233] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Kathryn E. Knowles
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Kimberly H. Hartstein
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Troy B. Kilburn
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Arianna Marchioro
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Heidi D. Nelson
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Patrick J. Whitham
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Daniel R. Gamelin
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| |
Collapse
|
21
|
Gogoi M, Chattopadhyay A. White light emission from quantum dot and a UV-visible emitting Pd-complex on its surface. RSC Adv 2016. [DOI: 10.1039/c6ra22985a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Near white light emission (CIE 0.35, 0.29) has been achieved as a combination of intraligand transition, aggregate induced emission and dopant emission followed by surface complexation on Qdot surface.
Collapse
Affiliation(s)
- Madhulekha Gogoi
- Department of Chemistry and Centre for Nanotechnology
- Indian Institute of Technology Guwahati
- Guwahati-781039
- India
| | - Arun Chattopadhyay
- Department of Chemistry and Centre for Nanotechnology
- Indian Institute of Technology Guwahati
- Guwahati-781039
- India
| |
Collapse
|
22
|
Li M, Xu C, Wu L, Wu P, Hou X. Dually enriched Cu:CdS@ZnS QDs with both polyvinylpyrrolidone twisting and SiO2 loading for improved cell imaging. Chem Commun (Camb) 2015; 51:3552-5. [PMID: 25626901 DOI: 10.1039/c4cc10127h] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Through harvesting of the increased Stokes shift of CdS QDs via Cu-doping, the concentration-quenching or aggregation-quenching of CdS QDs was largely alleviated. A dually-enriched strategy with both polyvinylpyrrolidone (PVP) twisting and SiO2 loading was developed for generating a highly luminescent doped-dots (d-dots) assembly for improved cell imaging.
Collapse
Affiliation(s)
- Mei Li
- Analytical & Testing Center, Sichuan University, 29 Wangjiang Road, Chengdu 610064, China.
| | | | | | | | | |
Collapse
|
23
|
Knowles KE, Nelson HD, Kilburn TB, Gamelin DR. Singlet-Triplet Splittings in the Luminescent Excited States of Colloidal Cu(+):CdSe, Cu(+):InP, and CuInS2 Nanocrystals: Charge-Transfer Configurations and Self-Trapped Excitons. J Am Chem Soc 2015; 137:13138-47. [PMID: 26389577 DOI: 10.1021/jacs.5b08547] [Citation(s) in RCA: 100] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The electronic and magnetic properties of the luminescent excited states of colloidal Cu(+):CdSe, Cu(+):InP, and CuInS2 nanocrystals were investigated using variable-temperature photoluminescence (PL) and magnetic circularly polarized luminescence (MCPL) spectroscopies. The nanocrystal electronic structures were also investigated by absorption and magnetic circular dichroism (MCD) spectroscopies. By every spectroscopic measure, the luminescent excited states of all three materials are essentially indistinguishable. All three materials show very similar broad PL line widths and large Stokes shifts. All three materials also show similar temperature dependence of their PL lifetimes and MCPL polarization ratios. Analysis shows that this temperature dependence reflects Boltzmann population distributions between luminescent singlet and triplet excited states with average singlet-triplet splittings of ∼1 meV in each material. These similarities lead to the conclusion that the PL mechanism in CuInS2 NCs is fundamentally different from that of bulk CuInS2 and instead is the same as that in Cu(+)-doped NCs, which are known to luminesce via charge-transfer recombination of conduction-band electrons with copper-localized holes. The luminescence of CuInS2 nanocrystals is explained well by invoking exciton self-trapping, in which delocalized photogenerated holes contract in response to strong vibronic coupling at lattice copper sites to form a luminescent excited state that is essentially identical to that of the Cu(+)-doped semiconductor nanocrystals.
Collapse
Affiliation(s)
- Kathryn E Knowles
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
| | - Heidi D Nelson
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
| | - Troy B Kilburn
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
| | - Daniel R Gamelin
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
| |
Collapse
|
24
|
Whitham PJ, Knowles KE, Reid PJ, Gamelin DR. Photoluminescence Blinking and Reversible Electron Trapping in Copper-Doped CdSe Nanocrystals. NANO LETTERS 2015; 15:4045-51. [PMID: 26007328 DOI: 10.1021/acs.nanolett.5b01046] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Single-particle photoluminescence blinking is observed in the copper-centered deep-trap luminescence of copper-doped CdSe (Cu(+):CdSe) nanocrystals. Blinking dynamics for Cu(+):CdSe and undoped CdSe nanocrystals are analyzed to identify the effect of Cu(+), which selectively traps photogenerated holes. Analysis of the blinking data reveals that the Cu(+):CdSe and CdSe nanocrystal "off"-state dynamics are statistically identical, but the Cu(+):CdSe nanocrystal "on" state is shorter lived. Additionally, a new and pronounced temperature-dependent delayed luminescence is observed in the Cu(+):CdSe nanocrystals that persists long beyond the radiative lifetime of the luminescent excited state. This delayed luminescence is analogous to the well-known donor-acceptor pair luminescence of bulk copper-doped phosphors and is interpreted as revealing metastable charge-separated excited states formed by reversible electron trapping at the nanocrystal surfaces. A mechanistic link between this delayed luminescence and the luminescence blinking is proposed. Collectively, these data suggest that electron (rather than hole) trapping/detrapping is responsible for photoluminescence intermittency in these nanocrystals.
Collapse
Affiliation(s)
- Patrick J Whitham
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Kathryn E Knowles
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Philip J Reid
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Daniel R Gamelin
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| |
Collapse
|
25
|
Ding SJ, Liang S, Nan F, Liu XL, Wang JH, Zhou L, Yu XF, Hao ZH, Wang QQ. Synthesis and enhanced fluorescence of Ag doped CdTe semiconductor quantum dots. NANOSCALE 2015; 7:1970-6. [PMID: 25536020 DOI: 10.1039/c4nr05731g] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Doping with intentional impurities is an intriguing way to tune the properties of semiconductor nanocrystals. However, the synthesis of some specific doped semiconductor nanocrystals remains a challenge and the doping mechanism in this strongly confined system is still not clearly understood. In this work, we report, for the first time, the synthesis of stable and water-soluble Ag-doped CdTe semiconductor quantum dots (SQDs) via a facile aqueous approach. Experimental characterization demonstrated the efficient doping of the Ag impurities into the CdTe SQDs with an appropriate reaction time. By doping 0.3% Ag impurities, the Stokes shift is decreased by 120 meV, the fluorescence intensity is enhanced more than 3 times, the radiative rate is enhanced 4.2 times, and the non-radiative rate is efficiently suppressed. These observations reveal that the fluorescence enhancement in Ag-doped CdTe SQDs is mainly attributed to the minimization of surface defects, filling of the trap states, and the enhancement of the radiative rate by the silver dopants. Our results suggest that the silver doping is an efficient method for tuning the optical properties of the CdTe SQDs.
Collapse
Affiliation(s)
- Si-Jing Ding
- Department of Physics, Institute for Advanced Studies, and Key Laboratory of Artificial Micro- and Nano-structures of the Ministry of Education, Wuhan University, Wuhan, 430072, P. R. China.
| | | | | | | | | | | | | | | | | |
Collapse
|
26
|
Liu M, Yao W, Li C, Wu Z, Li L. Tuning emission and Stokes shift of CdS quantum dots via copper and indium co-doping. RSC Adv 2015. [DOI: 10.1039/c4ra11349g] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Cu and In co-doped CdS QDs are synthesized and exhibit large Stokes shifts and tunable emission from green to near-infrared.
Collapse
Affiliation(s)
- Mingming Liu
- School of Environmental Science and Engineering
- Shanghai Jiao Tong University
- Shanghai
- China
- School of Chemistry and Chemical Engineering
| | - Wei Yao
- School of Environmental Science and Engineering
- Shanghai Jiao Tong University
- Shanghai
- China
- College of Chemistry and Chemical Engineering
| | - Cun Li
- School of Chemistry and Chemical Engineering
- Anhui University
- Hefei
- China
| | - Zhenyu Wu
- School of Chemistry and Chemical Engineering
- Anhui University
- Hefei
- China
| | - Liang Li
- School of Environmental Science and Engineering
- Shanghai Jiao Tong University
- Shanghai
- China
| |
Collapse
|
27
|
Grandhi GK, Swathi K, Narayan KS, Viswanatha R. Cu Doping in Ligand Free CdS Nanocrystals: Conductivity and Electronic Structure Study. J Phys Chem Lett 2014; 5:2382-9. [PMID: 26279564 DOI: 10.1021/jz5009664] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Ligand-free Cu-doped CdS nanocrystals (NCs) have been synthesized to elucidate their surface electronic structure. The Cu-doped ligand-free NCs unlike their undoped counterparts are shown to be luminescent. We used this Cu-related emission as a probe to study the nature of the surface trap states that results in negligible luminescence in the undoped NCs. The concentration of the sulfide ligands is shown to play a crucial role in the surface passivation of the NCs. Electrical conductivity of these NCs was also studied, and they were shown to exhibit significant conductivity of ∼10(-4) S cm(-1). Further we have shown that the electrical conductivity is closely correlated to the surface charge and hence the trap states of the individual NCs have far-reaching consequences in the device optimization.
Collapse
Affiliation(s)
- G Krishnamurthy Grandhi
- †New Chemistry Unit, §Chemistry and Physics of Materials Unit, and ‡International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India
| | - K Swathi
- †New Chemistry Unit, §Chemistry and Physics of Materials Unit, and ‡International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India
| | - K S Narayan
- †New Chemistry Unit, §Chemistry and Physics of Materials Unit, and ‡International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India
| | - Ranjani Viswanatha
- †New Chemistry Unit, §Chemistry and Physics of Materials Unit, and ‡International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India
| |
Collapse
|
28
|
|