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Zeng Y, Liu X, Liu Y, Chen W, Liu F, Li H. 22% Record Efficiency in Nanorod Light-Emitting Diodes Achieved by Gradient Shells. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2310705. [PMID: 38377984 DOI: 10.1002/adma.202310705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2023] [Revised: 01/08/2024] [Indexed: 02/22/2024]
Abstract
The external quantum efficiency (EQE) in light-emitting diodes (LEDs) based on isotropic quantum dots has approached the theoretical limit of close to 20%. Anisotropic nanorods can break this limit by taking advantage of their directional emission. However, the progress towards higher EQE by using CdSe/CdS nanorods (NRs) faces several challenges, primarily involving the low quantum yield and unbalanced charge injection in devices. Herein, the seeded growth method is modified and anisotropic nanorods are obtained with photoluminescence quantum yield up to 98% by coating a gradient alloyed CdZnSe shell around conventional spherical CdSe seeds. This intermediate alloyed CdZnSe shell combined with a subsequent rod-shaped CdZnS/ZnS shell can effectively suppress the electron delocalization in the typical CdSe/CdS nanorods due to their small conduction bandgap offset. Additionally, this alloyed shell can reduce the hole-injection barrier and create a larger barrier for electron injection, both effects promoting a balanced injection of electrons and holes in LEDs. Hence, LEDs are reached with high brightness (160341 cd m-2) and high efficiency (EQE = 22%, current efficiency = 23.19 cd A-1), which are the highest values to date for nanorod LEDs.
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Affiliation(s)
- Yicheng Zeng
- Experimental Center of Advanced Materials, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, 100081, China
| | - Xiaonan Liu
- Experimental Center of Advanced Materials, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, 100081, China
| | - Yuan Liu
- State Key Laboratory of Molecular Reaction Dynamics and Dynamics Research Center for Energy and Environmental Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
| | - Weiwei Chen
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Fangze Liu
- Advanced Research Institute of Multidisciplinary Sciences, Beijing Institute of Technology, Beijing, 100081, China
| | - Hongbo Li
- Experimental Center of Advanced Materials, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, 100081, China
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Drake GA, Keating LP, Huang C, Shim M. Colloidal Multi-Dot Nanorods. J Am Chem Soc 2024; 146:9074-9083. [PMID: 38517010 DOI: 10.1021/jacs.3c14115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2024]
Abstract
Colloidal nanorod heterostructures consisting of multiple quantum dots within a nanorod (n-DNRs, where n is the number of quantum dots within a nanorod) are synthesized with alternating segments of CdSe "dot" and CdS "rod" via solution heteroepitaxy. The reaction temperature, time dependent ripening, and asymmetry of the wurtzite lattice and the resulting anisotropy of surface ligand steric hindrance are exploited to vary the morphology of the growing quantum dot segments. The alternating CdSe and CdS growth steps can be easily repeated to increment the dot number in unidirectional or bidirectional growth regimes. As an initial exploration of electron occupation effects on their optical properties, asymmetric 2-DNRs consisting of two dots of different lengths and diameters are synthesized and are shown to exhibit a change in color and an unusual photoluminescence quantum yield increase upon photochemical doping.
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Affiliation(s)
- Gryphon A Drake
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Logan P Keating
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Conan Huang
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Moonsub Shim
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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Sheikh T, Mir WJ, Nematulloev S, Maity P, Yorov KE, Hedhili MN, Emwas AH, Khan MS, Abulikemu M, Mohammed OF, Bakr OM. InAs Nanorod Colloidal Quantum Dots with Tunable Bandgaps Deep into the Short-Wave Infrared. ACS NANO 2023; 17:23094-23102. [PMID: 37955579 DOI: 10.1021/acsnano.3c08796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2023]
Abstract
InAs colloidal quantum dots (CQDs) have emerged as candidate lead- and mercury-free solution-processed semiconductors for infrared technology due to their appropriate bulk bandgap, which can be tuned by quantum confinement, and promising charge-carrier transport properties. However, the lack of suitable arsenic precursors and readily accessible synthesis conditions have limited InAs CQDs to smaller sizes (<7 nm), with bandgaps largely restricted to <1400 nm in the near-infrared spectral window. Conventional InAs CQD synthesis requires highly reactive, hazardous arsenic precursors, which are commercially scarce, making the synthesis hard to control and study. Here, we present a controlled synthesis strategy (using only readily available and less reactive precursors) to overcome the practical wavelength limitation of InAs CQDs, achieving monodisperse InAs nanorod CQDs with bandgaps tunable from ∼1200 to ∼1800 nm, thus crossing deep into the short-wave infrared (SWIR) region. By controlling the reactivity through in situ precursor complexation, we isolate the reaction mechanism, producing InAs nanorod CQDs that display narrow excitonic features and efficient carrier multiplication. Our work enables InAs CQDs for a wider range of SWIR applications.
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Affiliation(s)
- Tariq Sheikh
- KAUST Catalysis Center (KCC), Division of Physical Sciences and Engineering (PSE), King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Wasim J Mir
- KAUST Catalysis Center (KCC), Division of Physical Sciences and Engineering (PSE), King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Saidkhodzha Nematulloev
- KAUST Catalysis Center (KCC), Division of Physical Sciences and Engineering (PSE), King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Partha Maity
- KAUST Catalysis Center (KCC), Division of Physical Sciences and Engineering (PSE), King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
- Advanced Membranes and Porous Materials Center, Division of Physical Science and Engineering, Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Khursand E Yorov
- KAUST Catalysis Center (KCC), Division of Physical Sciences and Engineering (PSE), King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Mohamed Nejib Hedhili
- KAUST Core Laboratories, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Abdul-Hamid Emwas
- KAUST Core Laboratories, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Mudeha Shafat Khan
- KAUST Catalysis Center (KCC), Division of Physical Sciences and Engineering (PSE), King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Mutalifu Abulikemu
- KAUST Catalysis Center (KCC), Division of Physical Sciences and Engineering (PSE), King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Omar F Mohammed
- KAUST Catalysis Center (KCC), Division of Physical Sciences and Engineering (PSE), King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
- Advanced Membranes and Porous Materials Center, Division of Physical Science and Engineering, Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Osman M Bakr
- KAUST Catalysis Center (KCC), Division of Physical Sciences and Engineering (PSE), King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
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Abstract
Anisotropic heterostructures of colloidal nanocrystals embed size-, shape-, and composition-dependent electronic structure within variable three-dimensional morphology, enabling intricate design of solution-processable materials with high performance and programmable functionality. The key to designing and synthesizing such complex materials lies in understanding the fundamental thermodynamic and kinetic factors that govern nanocrystal growth. In this review, nanorod heterostructures, the simplest of anisotropic nanocrystal heterostructures, are discussed with respect to their growth mechanisms. The effects of crystal structure, surface faceting/energies, lattice strain, ligand sterics, precursor reactivity, and reaction temperature on the growth of nanorod heterostructures through heteroepitaxy and cation exchange reactions are explored with currently known examples. Understanding the role of various thermodynamic and kinetic parameters enables the controlled synthesis of complex nanorod heterostructures that can exhibit unique tailored properties. Selected application prospects arising from such capabilities are then discussed.
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Affiliation(s)
- Gryphon A Drake
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 United States
| | - Logan P Keating
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 United States
| | - Moonsub Shim
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 United States
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