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Lei H, Lv L, Zhou X, Liu S, Zhu M, Wang H, Qin H, Fang Q, Peng X. Weakly Confined Semiconductor Nanocrystals Excel in Photochemical and Optoelectronic Properties: Evidence from Single-Dot Studies. J Am Chem Soc 2024; 146:21948-21959. [PMID: 39075033 DOI: 10.1021/jacs.4c06993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/31/2024]
Abstract
Single-molecule spectroscopy offers state-resolved measurements on charge-transfer reactions of single semiconductor nanocrystals, leading to the discovery of up to six single-charge transfer reactions with seven transient states for single CdSe/CdS core/shell nanocrystals with water (or oxygen) as the hole (or electron) acceptors. Kinetic rates of three photoinduced single-hole transfer reactions decrease significantly upon increasing the number of excess electrons in a nanocrystal, mainly due to efficient Auger nonradiative recombination of the charged single excitons. Conversely, the kinetic rates of three single-electron transfer reactions of an unexcited nanocrystal increase proportionally to the number of excess electrons in it. Results here reveal that charge-transfer reactions of nanocrystals, at the center of nearly all their functions, could only be deciphered at a state-resolved level on a single nanocrystal. Size-dependent studies validate the weakly confined semiconductor nanocrystals, instead of strongly confined ones (quantum dots), as optimal candidates for photochemical and optoelectronic applications.
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Affiliation(s)
- Haixin Lei
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310058, China
| | - Liulin Lv
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310058, China
| | - Xionglin Zhou
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310058, China
| | - Shaojie Liu
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310058, China
| | - Meiyi Zhu
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310058, China
| | - Huifeng Wang
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310058, China
| | - Haiyan Qin
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310058, China
| | - Qun Fang
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310058, China
| | - Xiaogang Peng
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310058, China
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2
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Cao Z, Li C, Shu Y, Zhu M, Su B, Qin H, Peng X. Unraveling Mechanisms of Highly Efficient Yet Stable Electrochemiluminescence from Quantum Dots. J Am Chem Soc 2023; 145:26425-26434. [PMID: 37976033 DOI: 10.1021/jacs.3c10556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2023]
Abstract
With CdSe/CdS/ZnS core/shell/shell quantum dots (QDs) as the model system, time- and potential-resolved spectroelectrochemical measurements are successfully applied for studying the general mechanisms and kinetics of electrochemiluminescence (ECL) generation. The rate constant of electron injection from the cathode into a QD to form a negatively charged QD (QD-) increases monotonically from -0.88 V to -1.2 V (vs Ag/AgCl). Mainly due to the deep LUMO of the QDs, the resulting QD- as the key intermediate for ECL generation is structurally stable and possesses very slow spontaneous deionization channels. The latter (the main non-ECL channels) are usually 3-4 orders of magnitude slower than the rate constant of the successive hole injection from an active co-reactant into a QD-. The kinetic studies quantify the internal ECL quantum yield of ideal QD ECL emitters to be nearly identical to that of photoluminescence, which is near unity for the current system. Identification of the key intermediate, discovery of the related elementary steps, and determination of all rate constants not only establish a general framework for understanding ECL generation but also offer basic design rules for ECL emitters.
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Affiliation(s)
- Zhiyuan Cao
- Key Laboratory of Excited-State Materials of Zhejiang Province and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Chuyue Li
- Key Laboratory of Excited-State Materials of Zhejiang Province and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Yufei Shu
- Key Laboratory of Excited-State Materials of Zhejiang Province and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Meiyi Zhu
- Key Laboratory of Excited-State Materials of Zhejiang Province and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Bin Su
- Key Laboratory of Excited-State Materials of Zhejiang Province and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Haiyan Qin
- Key Laboratory of Excited-State Materials of Zhejiang Province and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Xiaogang Peng
- Key Laboratory of Excited-State Materials of Zhejiang Province and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
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3
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Lei H, Liu S, Li J, Li C, Qin H, Peng X. Band-Edge Energy Levels of Dynamic Excitons in Cube-Shaped CdSe/CdS Core/Shell Nanocrystals. ACS NANO 2023; 17:21962-21972. [PMID: 37901990 DOI: 10.1021/acsnano.3c08377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/31/2023]
Abstract
An electron-hole pair in a cube-shaped CdSe/CdS core/shell nanocrystal exists in the form of dynamic excitons across the strongly and weakly confined regimes under ambient temperatures. Photochemical doping is applied to distinguish the band-edge electron and hole levels, confirming an effective mass model with universal constants. Reduction of the optical bandgap upon epitaxy of the CdS shells is caused by lowering the band-edge electron level and barely affecting the band-edge hole level. Similar shifts of the electron levels, yet retaining the hole levels, can switch the order in energy of the three lowest-energy transitions. Thermal distribution of 1-4 electrons among the two thermally accessible electron levels follows number-counting statistics, instead of Fermi-Dirac distribution.
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Affiliation(s)
- Haixin Lei
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Shaojie Liu
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Jiongzhao Li
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Chuyue Li
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Haiyan Qin
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Xiaogang Peng
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
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4
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Wang L, Xiang D, Gao K, Wang J, Wu K. Colloidal n-Doped CdSe and CdSe/ZnS Nanoplatelets. J Phys Chem Lett 2021; 12:11259-11266. [PMID: 34766755 DOI: 10.1021/acs.jpclett.1c02856] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Colloidal semiconductor nanoplatelets (NPLs) are chemical versions of well-studied quantum wells (QWs). For QWs, gating and carrier doping are standard tools to manipulate their optical, electric, or magnetic properties. It would be highly desirable to use pure chemical methods to dope extra charge carriers into free-standing colloidal NPLs to achieve a similar level of manipulation. Here we report colloidal n-doped CdSe and CdSe/ZnS NPLs achieved through a photochemical doping method. The extra electrons doped into the conduction band edges are evidenced by exciton absorption bleaches recoverable through dedoping and the appearance of new intersub-band transitions in the near-infrared. A high surface ligand coverage is the key to successful doping; otherwise, the doped electrons can be depleted likely by unpassivated surface cations. Large trion binding energies of 20-30 meV are found for the n-doped CdSe NPLs, which, in contrast, are reduced by 1 order of magnitude in CdSe/ZnS core/shell NPLs due to dielectric screening. Furthermore, we identify a long-lived negative trion with a lifetime of 1.5-1.6 ns that is likely dominated by radiative recombination.
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Affiliation(s)
- Lifeng Wang
- 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 116023, Liaoning, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Dongmei Xiang
- 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 116023, Liaoning, China
| | - Kaimin Gao
- 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 116023, Liaoning, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Junhui Wang
- 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 116023, Liaoning, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Kaifeng Wu
- 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 116023, Liaoning, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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5
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van der Stam W, Grimaldi G, Geuchies JJ, Gudjonsdottir S, van Uffelen PT, van Overeem M, Brynjarsson B, Kirkwood N, Houtepen AJ. Electrochemical Modulation of the Photophysics of Surface-Localized Trap States in Core/Shell/(Shell) Quantum Dot Films. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2019; 31:8484-8493. [PMID: 31666761 PMCID: PMC6814269 DOI: 10.1021/acs.chemmater.9b02908] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 09/23/2019] [Indexed: 05/03/2023]
Abstract
In this work, we systematically study the spectroelectrochemical response of CdSe quantum dots (QDs), CdSe/CdS core/shell QDs with varying CdS shell thicknesses, and CdSe/CdS/ZnS core/shell/shell QDs in order to elucidate the influence of localized surface trap states on the optoelectronic properties. By correlating the differential absorbance and the photoluminescence upon electrochemically raising the Fermi level, we reveal that trap states near the conduction band (CB) edge give rise to nonradiative recombination pathways regardless of the CdS shell thickness, evidenced by quenching of the photoluminescence before the CB edge is populated with electrons. This points in the direction of shallow trap states localized on the CdS shell surface that give rise to nonradiative recombination pathways. We suggest that these shallow trap states reduce the quantum yield because of enhanced hole trapping when the Fermi level is raised electrochemically. We show that these shallow trap states are removed when additional wide band gap ZnS shells are grown around the CdSe/CdS core/shell QDs.
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6
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Xie Y, Yu S, Zhang L, Du N, Yang M. Radiative and non-radiative decay kinetics of (CdSe)N (N = 3 and 4) clusters. J Chem Phys 2019. [DOI: 10.1063/1.5109068] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Affiliation(s)
- Yujuan Xie
- Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
| | - Shengping Yu
- College of Chemistry and Environment Protection Engineering, Southwest University for Nationalities, Chengdu 610041, People’s Republic of China
| | - Li Zhang
- Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
| | - Ning Du
- Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
| | - Mingli Yang
- Key Laboratory of High Energy Density Physics of Ministry of Education, Research Center for Materials Genome Engineering, Sichuan University, Chengdu 610065, China
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7
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Hou X, Kang J, Qin H, Chen X, Ma J, Zhou J, Chen L, Wang L, Wang LW, Peng X. Engineering Auger recombination in colloidal quantum dots via dielectric screening. Nat Commun 2019; 10:1750. [PMID: 30988287 PMCID: PMC6465357 DOI: 10.1038/s41467-019-09737-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 03/22/2019] [Indexed: 11/09/2022] Open
Abstract
Auger recombination is the main non-radiative decay pathway for multi-carrier states of colloidal quantum dots, which affects performance of most of their optical and optoelectronic applications. Outstanding single-exciton properties of CdSe/CdS core/shell quantum dots enable us to simultaneously study the two basic types of Auger recombination channels-negative trion and positive trion channels. Though Auger rates of positive trion are regarded to be much faster than that of negative trion for II-VI quantum dots in literature, our experiments find the two rates can be inverted for certain core/shell geometries. This is confirmed by theoretical calculations as a result of geometry-dependent dielectric screening. By varying the core/shell geometry, both types of Auger rates can be independently tuned for ~ 1 order of magnitude. Experimental and theoretical findings shed new light on designing quantum dots with necessary Auger recombination characteristics for high-power light-emitting-diodes, lasers, single-molecular tracking, super-resolution microscope, and advanced quantum light sources.
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Affiliation(s)
- Xiaoqi Hou
- Center for Chemistry of Novel & High-Performance Materials, and Department of Chemistry, Zhejiang University, 310027, Hangzhou, People's Republic of China
| | - Jun Kang
- Material Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Haiyan Qin
- Center for Chemistry of Novel & High-Performance Materials, and Department of Chemistry, Zhejiang University, 310027, Hangzhou, People's Republic of China.
| | - Xuewen Chen
- School of Physics, Huazhong University of Science and Technology, 430074, Wuhan, People's Republic of China
| | - Junliang Ma
- Center for Chemistry of Novel & High-Performance Materials, and Department of Chemistry, Zhejiang University, 310027, Hangzhou, People's Republic of China
| | - Jianhai Zhou
- Center for Chemistry of Novel & High-Performance Materials, and Department of Chemistry, Zhejiang University, 310027, Hangzhou, People's Republic of China
| | - Liping Chen
- Center for Chemistry of Novel & High-Performance Materials, and Department of Chemistry, Zhejiang University, 310027, Hangzhou, People's Republic of China
| | - Linjun Wang
- Center for Chemistry of Novel & High-Performance Materials, and Department of Chemistry, Zhejiang University, 310027, Hangzhou, People's Republic of China
| | - Lin-Wang Wang
- Material Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
| | - Xiaogang Peng
- Center for Chemistry of Novel & High-Performance Materials, and Department of Chemistry, Zhejiang University, 310027, Hangzhou, People's Republic of China.
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8
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Wan M, Cui S, Wei W, Cui S, Chen K, Chen W, Mi L. Bi-component synergic effect in lily-like CdS/Cu7S4 QDs for dye degradation. RSC Adv 2019; 9:2441-2450. [PMID: 35520484 PMCID: PMC9059895 DOI: 10.1039/c8ra09331h] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 12/21/2018] [Indexed: 12/31/2022] Open
Abstract
CdS has attracted extensive attention in the photocatalytic degradation of wastewater due to its relatively narrow bandgap and various microstructures. Previous reports have focused on CdS coupled with other semiconductors to reduce the photocorrosion and improve the photocatalytic performance. Herein, a 3D hierarchical CdS/Cu7S4 nanostructure was synthesized by cation exchange using lily-like CdS as template. The heterojunction material completely inherits the special skeleton of the template material and optimizes the nano-scale morphology, and achieves the transformation from nanometer structure to quantum dots (QDs). The introduction of Cu ions not only tuned the band gap of the composites to promote the utilization of solar photons, more importantly, Fenton-like catalysis was combined into the degradation process. Compared with the experiments of organic dye degradation under different illumination conditions, the degradability of the CdS/Cu7S4 QDs is greatly superior to pure CdS. Therefore, the constructed CdS/Cu7S4 QDs further realized the optimization of degradation performance by the synergic effect of photo-catalysis and Fenton-like catalysis. CdS has attracted extensive attention in the photocatalytic degradation of wastewater due to its relatively narrow bandgap and various microstructures.![]()
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Affiliation(s)
- Mengli Wan
- Center for Advanced Materials Research
- Zhongyuan University of Technology
- Zhengzhou 450007
- China
- College of Chemistry and Molecular Engineering
| | - Shizhong Cui
- Center for Advanced Materials Research
- Zhongyuan University of Technology
- Zhengzhou 450007
- China
| | - Wutao Wei
- Center for Advanced Materials Research
- Zhongyuan University of Technology
- Zhengzhou 450007
- China
| | - Siwen Cui
- Center for Advanced Materials Research
- Zhongyuan University of Technology
- Zhengzhou 450007
- China
| | - Kongyao Chen
- Center for Advanced Materials Research
- Zhongyuan University of Technology
- Zhengzhou 450007
- China
| | - Weihua Chen
- College of Chemistry and Molecular Engineering
- Zhengzhou University
- Zhengzhou 450001
- China
| | - Liwei Mi
- Center for Advanced Materials Research
- Zhongyuan University of Technology
- Zhengzhou 450007
- China
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9
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Limpens R, Neale NR. Free electron-driven photophysics in n-type doped silicon nanocrystals. NANOSCALE 2018; 10:12068-12077. [PMID: 29911215 DOI: 10.1039/c8nr02173b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Although there have been extensive speculation regarding the applicability of doped silicon nanocrystals (Si NCs) in optoelectronic technologies, a quantitative analysis on the photophysical workings of introduced free carriers remains elusive. Here, we present a comprehensive study on the photophysics of ∼7.5 nm heavily phosphorous-doped Si NCs, using a combination of spectroscopic techniques. We correlate the carrier dynamics with the location of the free carriers - which we tune from NC core to surface depending on the state of oxidation. The strength of the Coulomb interactions between the photoexcited electron-hole pairs and the doping-induced free carriers depends on (1) the concentration of free carriers, (2) the location of these carriers, and (3) the diameter of the NCs. In contrast to prior studies, the photoexcited carrier dynamics in these n-type doped Si NCs are dominated by strong Coulomb interactions with doping-induced free electrons, characterized by a negative trion lifetime of around 9 ns. While radiative recombination in doped direct bandgap NCs can often still compete with trion recombination (allowing emission to be present), emission in our doped Si NCs is completely quenched due to the relatively slow radiative recombination in these indirect bandgap NCs. Furthermore, multi-exciton interaction times are slightly shortened compared to those of intrinsic Si NCs, which we attribute to an increased number of free electrons, enhancing the oscillator strength of Auger recombination. These results constitute a framework for the optimization of doped Si NC synthesis techniques and device engineering directions for future doped-Si NC-based optoelectronic and photovoltaic applications.
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Affiliation(s)
- R Limpens
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA.
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10
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Orfield NJ, Majumder S, McBride JR, Yik-Ching Koh F, Singh A, Bouquin SJ, Casson JL, Johnson AD, Sun L, Li X, Shih CK, Rosenthal SJ, Hollingsworth JA, Htoon H. Photophysics of Thermally-Assisted Photobleaching in "Giant" Quantum Dots Revealed in Single Nanocrystals. ACS NANO 2018; 12:4206-4217. [PMID: 29709173 DOI: 10.1021/acsnano.7b07450] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Quantum dots (QDs) are steadily being implemented as down-conversion phosphors in market-ready display products to enhance color rendering, brightness, and energy efficiency. However, for adequate longevity, QDs must be encased in a protective barrier that separates them from ambient oxygen and humidity, and device architectures are designed to avoid significant heating of the QDs as well as direct contact between the QDs and the excitation source. In order to increase the utility of QDs in display technologies and to extend their usefulness to more demanding applications as, for example, alternative phosphors for solid-state lighting (SSL), QDs must retain their photoluminescence emission properties over extended periods of time under conditions of high temperature and high light flux. Doing so would simplify the fabrication costs for QD display technologies and enable QDs to be used as down-conversion materials in light-emitting diodes for SSL, where direct-on-chip configurations expose the emitters to temperatures approaching 100 °C and to photon fluxes from 0.1 W/mm2 to potentially 10 W/mm2. Here, we investigate the photobleaching processes of single QDs exposed to controlled temperature and photon flux. In particular, we investigate two types of room-temperature-stable core/thick-shell QDs, known as "giant" QDs for which shell growth is conducted using either a standard layer-by-layer technique or by a continuous injection method. We determine the mechanistic pathways responsible for thermally-assisted photodegradation, distinguishing effects of hot-carrier trapping and QD charging. The findings presented here will assist in the further development of advanced QD heterostructures for maximum device lifetime stability.
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Affiliation(s)
- Noah J Orfield
- Materials Physics and Applications Division: Center for Integrated Nanotechnologies , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Somak Majumder
- Materials Physics and Applications Division: Center for Integrated Nanotechnologies , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - James R McBride
- Department of Chemistry , Vanderbilt University , Nashville , Tennessee 37235 , United States
| | - Faith Yik-Ching Koh
- Materials Physics and Applications Division: Center for Integrated Nanotechnologies , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Ajay Singh
- Materials Physics and Applications Division: Center for Integrated Nanotechnologies , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Sarah J Bouquin
- Materials Physics and Applications Division: Center for Integrated Nanotechnologies , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Joanna L Casson
- Chemistry Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Alex D Johnson
- Physics Department and Center for Complex Quantum Systems , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Liuyang Sun
- Physics Department and Center for Complex Quantum Systems , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Xiaoqin Li
- Physics Department and Center for Complex Quantum Systems , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Chih-Kang Shih
- Physics Department and Center for Complex Quantum Systems , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Sandra J Rosenthal
- Department of Chemistry , Vanderbilt University , Nashville , Tennessee 37235 , United States
| | - Jennifer A Hollingsworth
- Materials Physics and Applications Division: Center for Integrated Nanotechnologies , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Han Htoon
- Materials Physics and Applications Division: Center for Integrated Nanotechnologies , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
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11
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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.
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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
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12
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Guo T, Sampat S, Rupich SM, Hollingsworth JA, Buck M, Htoon H, Chabal YJ, Gartstein YN, Malko AV. Biexciton and trion energy transfer from CdSe/CdS giant nanocrystals to Si substrates. NANOSCALE 2017; 9:19398-19407. [PMID: 29210416 DOI: 10.1039/c7nr06272a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Observation of energy transfer (ET) from multiexcitonic (MX) complexes in nanocrystal quantum dots (NQDs) has been severely restricted due to efficient nonradiative Auger recombination leading to very low MX emission quantum yields. Here we employed "giant" CdSe/CdS NQDs with suppressed Auger recombination to study ET of biexcitons (BX) and charged excitons (trions) into Si substrate. Photoluminescence (PL) measurements of (sub)monolayers of gNQDs controllably assembled on various interacting surfaces and augmented by single gNQD's imaging reveal appearance of BX spectral signatures and progressive acceleration of PL lifetimes of all excitonic species on Si substrates. From statistical analysis of a large number of PL lifetime traces, representative exciton, trion and BX ET efficiencies are measured as ∼75%, 55% and 45% respectively. Detailed analysis of the MX's radiative rates demonstrate the crucial role of the radiative (waveguide) ET in maintaining high overall transfer efficiency despite the prevalent Auger recombination. Our observations point towards practical utilization of MX-bearing nanocrystals in future optoelectronics architectures.
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Affiliation(s)
- Tianle Guo
- Department of Physics, The University of Texas at Dallas, Richardson, TX 75080, USA.
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