1
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Mulder JT, Monchen JOV, Vogel YB, Lin CT, Drago F, Caselli VM, Saikumar N, Savenije TJ, Houtepen AJ. Orthogonal Electrochemical Stability of Bulk and Surface in Lead Halide Perovskite Thin Films and Nanocrystals. J Am Chem Soc 2024. [PMID: 39177513 DOI: 10.1021/jacs.4c06340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/24/2024]
Abstract
Lead halide perovskites have attracted significant attention for their wide-ranging applications in optoelectronic devices. A ubiquitous element in these applications is that charging of the perovskite is involved, which can trigger electrochemical degradation reactions. Understanding the underlying factors governing these degradation processes is crucial for improving the stability of perovskite-based devices. For bulk semiconductors, the electrochemical decomposition potentials depend on the stabilization of atoms in the lattice-a parameter linked to the material's solubility. For perovskite nanocrystals (NCs), electrochemical surface reactions are strongly influenced by the binding equilibrium of passivating ligands. Here, we report a spectro-electrochemical study on CsPbBr3 NCs and bulk thin films in contact with various electrolytes, aimed at understanding the factors that control cathodic degradation. These measurements reveal that the cathodic decomposition of NCs is primarily determined by the solubility of surface ligands, with diminished cathodic degradation for NCs in high-polarity electrolyte solvents where ligand solubilities are lower. However, the solubility of the surface ligands and bulk lattice of NCs are orthogonal, such that no electrolyte could be identified where both the surface and bulk are stabilized against cathodic decomposition. This poses inherent challenges for electrochemical applications: (i) The electrochemical stability window of CsPbBr3 NCs is constrained by the reduction potential of dissolved Pb2+ complexes, and (ii) cathodic decomposition occurs well before the conduction band can be populated with electrons. Our findings provide insights to enhance the electrochemical stability of perovskite thin films and NCs, emphasizing the importance of a combined selection of surface passivation and electrolyte.
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Affiliation(s)
- Jence T Mulder
- Optoelectronic Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Julius O V Monchen
- Optoelectronic Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Yan B Vogel
- Optoelectronic Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Cheng Tai Lin
- Optoelectronic Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Filippo Drago
- Chemistry Facility, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova, Italy
| | - Valentina M Caselli
- Optoelectronic Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Niranjan Saikumar
- Department of Precision and Microsystems Engineering, Faculty of Mechanical Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands
| | - Tom J Savenije
- Optoelectronic Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Arjan J Houtepen
- Optoelectronic Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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2
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Ortiz Calderon FG, Gómez Pineros BS, McClenaghan ND, Granados-Oliveros G. Influence of Structural Properties of Oleic Acid-Capped CdSe/ZnS Quantum Dots in the Detection of Hg 2+ Ions. J Fluoresc 2024:10.1007/s10895-024-03828-0. [PMID: 39009903 DOI: 10.1007/s10895-024-03828-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2024] [Accepted: 06/24/2024] [Indexed: 07/17/2024]
Abstract
Oleic acid-capped CdSe/ZnS quantum dots (QDs) were used to investigate their photoluminescence (PL) response to Hg2+ ions as a function of the surface properties of QDs. Three distinctly-size CdSe/ZnS QDs were obtained by varying the molar ratio of shell precursors, which were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), Fourier-Transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), absorption spectroscopy, and time-resolved fluorescence spectroscopy. Results revealed the obtention of zinc blende nanocrystals with sizes ranging from 2.7 to 3.2 nm (± 0.5) and ZnS thickness between 0.3 and 1.0 monolayer (ML). The variation of the [S]/[Zn] molar ratio introduced chemical species that act as traps, affecting the PL properties differently. Depending on the thickness of the shell and chemical speciation on surface, Hg2+ ions could induce quenching or enhancement of PL. Detection of mercury ions was evaluated in terms of Stern-Volmer equation, where the limit of detection (LOD) for the PL quenching system was 11.2 nM, while for the PL enhancing systems were 8.98 nM and 10.7 nM. Results demonstrate the performance of oleic acid-capped CdSe/ZnS QDs to detect Hg2+ and their capacity to turn the PL on/off depending on surface properties.
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Affiliation(s)
- Fredy Giovany Ortiz Calderon
- Grupo de Síntesis Orgánica Sostenible, Departamento de Química, Facultad de Ciencias, Universidad Nacional de Colombia, Bogotá, DC, Colombia
- Institut des Sciences Moléculaires, CNRS UMR 5255, University of Bordeaux, Talence, 33405, France
| | - Brayan Stiven Gómez Pineros
- Grupo de Síntesis Orgánica Sostenible, Departamento de Química, Facultad de Ciencias, Universidad Nacional de Colombia, Bogotá, DC, Colombia
| | - Nathan D McClenaghan
- Institut des Sciences Moléculaires, CNRS UMR 5255, University of Bordeaux, Talence, 33405, France
| | - Gilma Granados-Oliveros
- Grupo de Síntesis Orgánica Sostenible, Departamento de Química, Facultad de Ciencias, Universidad Nacional de Colombia, Bogotá, DC, Colombia.
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3
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Huo X, Xie Y, Wang X, Zhang L, Yang M. Reduction reactions at the interface between CdS quantum dot and Z-type ligands driven by electron injection in the electroluminescent processes. J Chem Phys 2024; 161:024304. [PMID: 38984958 DOI: 10.1063/5.0196243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Accepted: 06/24/2024] [Indexed: 07/11/2024] Open
Abstract
The efficient and stable electroluminescence of quantum dots (QDs) is of great importance in their applications in new display technologies. The short service life of blue QDs, however, hinders their development and commercialization. Different mechanisms have been proposed for the destabilization of QDs in electroluminescent processes. Based on real-time time-dependent density functional theory studies on the QD models covered by Z-type ligands (XAc2, X = Cd, Zn, Mg), the structural evolution is simulated to reveal the mechanism of the reduction reactions induced by electron injection. Our simulations reproduce the experimental observations that the reduction reactions occur at the QD-ligand interface, and the reduced Cd atom is almost in a zero valence state. However, different sites are predicted for the reactions in which the surface metal atom of the QD instead of the metal atom in the ligands is reduced. As a result, one of the arms of the chelate ligand leaves the QD, which tends to cause damage to its electroluminescent performance. Our findings contribute to a mechanistic understanding of the reduction reactions that occurred at the QD-ligand interface.
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Affiliation(s)
- Xiangyu Huo
- Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
| | - Yujuan Xie
- School of Science, Westlake University, Hangzhou 310030, China
| | - Xian Wang
- School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
| | - Li Zhang
- Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
| | - Mingli Yang
- Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
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4
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Zhang M, Liu Z, Wang J, Chen Z, Jiang G, Zhang Q, Li Z. Generating Long-Lived Charge Carriers in CdS Quantum Dots by Cu-Doping for Photocatalytic CO 2 Reduction. Inorg Chem 2024; 63:2234-2240. [PMID: 38214981 DOI: 10.1021/acs.inorgchem.3c04196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2024]
Abstract
Converting CO2 into high-value-added chemicals has been recognized as a promising way to tackle the fossil fuel crisis. Quantum dots (QDs) have been extensively studied for photocatalytic CO2 reduction due to their excellent optoelectronic properties. However, most of the photogenerated charge carriers recombine before they participate in the photocatalytic reaction. It is crucial to regulate the charge carriers to minimize undesired charge recombination, thus, promoting surface photocatalysis. Herein, we report a copper-doped CdS (Cu:CdS) QD photocatalyst for CO2 reduction. Density functional theory simulations and experimental results demonstrate that Cu dopants create intermediate energy levels in CdS QDs that can extend the lifetime of exciton charge carriers. Furthermore, the long-lived charge carriers can be harnessed for the photocatalytic reaction on Cu:CdS QDs. The resultant Cu:CdS QDs exhibited a significantly enhanced photocatalytic activity toward CO2 reduction compared to the pristine CdS QDs. This work highlights the importance of charge regulation in photocatalysts and opens new pathways for the exploration of efficient QD photocatalysts.
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Affiliation(s)
- Meng Zhang
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua, Zhejiang 321004, P. R. China
| | - Zhihong Liu
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua, Zhejiang 321004, P. R. China
| | - Jin Wang
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua, Zhejiang 321004, P. R. China
- Zhejiang Institute of Photoelectronics, Zhejiang Normal University, Jinhua, Zhejiang 321004, P. R. China
| | - Zhihao Chen
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua, Zhejiang 321004, P. R. China
| | - Guocan Jiang
- Zhejiang Institute of Photoelectronics, Zhejiang Normal University, Jinhua, Zhejiang 321004, P. R. China
| | - Qiaowen Zhang
- Zhejiang Normal University, Jinhua, Zhejiang 321004, P. R. China
| | - Zhengquan Li
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua, Zhejiang 321004, P. R. China
- Zhejiang Institute of Photoelectronics, Zhejiang Normal University, Jinhua, Zhejiang 321004, P. R. China
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5
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Llusar J, du Fossé I, Hens Z, Houtepen A, Infante I. Surface Reconstructions in II-VI Quantum Dots. ACS NANO 2024; 18:1563-1572. [PMID: 38169474 PMCID: PMC10795476 DOI: 10.1021/acsnano.3c09265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 12/20/2023] [Accepted: 12/22/2023] [Indexed: 01/05/2024]
Abstract
Although density functional theory (DFT) calculations have been crucial in our understanding of colloidal quantum dots (QDs), simulations are commonly carried out on QD models that are significantly smaller than those generally found experimentally. While smaller models allow for efficient study of local surface configurations, increasing the size of the QD model will increase the size or number of facets, which can in turn influence the energetics and characteristics of trap formation. Moreover, core-shell structures can only be studied with QD models that are large enough to accommodate the different layers with the correct thickness. Here, we use DFT calculations to study the electronic properties of QDs as a function of size, up to a diameter of ∼4.5 nm. We show that increasing the size of QD models traditionally used in DFT studies leads to a disappearance of the band gap and localization of the HOMO and LUMO levels on facet-specific regions of the QD surface. We attribute this to the lateral coupling of surface orbitals and the formation of surface bands. The introduction of surface vacancies and their a posteriori refilling with Z-type ligands leads to surface reconstructions that widen the band gap and delocalize both the HOMO and LUMO. These results show that the surface geometry of the facets plays a pivotal role in defining the electronic properties of the QD.
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Affiliation(s)
- Jordi Llusar
- BCMaterials,
Basque Center for Materials, Applications, and Nanostructures, UPV/EHU Science Park, Leioa 48940, Spain
| | - Indy du Fossé
- Department
of Chemical Engineering, Optoelectronic Materials, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The
Netherlands
| | - Zeger Hens
- Physics
and Chemistry of Nanostructures, Department of Chemistry, and Center
of Nano and Biophotonics, Ghent University, B-9000 Gent, Belgium
| | - Arjan Houtepen
- Department
of Chemical Engineering, Optoelectronic Materials, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The
Netherlands
| | - Ivan Infante
- BCMaterials,
Basque Center for Materials, Applications, and Nanostructures, UPV/EHU Science Park, Leioa 48940, Spain
- Ikerbasque
Basque Foundation for Science, Bilbao 48009, Spain
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6
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Cao W, Yakimov A, Qian X, Li J, Peng X, Kong X, Copéret C. Surface Sites and Ligation in Amine-capped CdSe Nanocrystals. Angew Chem Int Ed Engl 2023; 62:e202312713. [PMID: 37869935 DOI: 10.1002/anie.202312713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 10/20/2023] [Accepted: 10/23/2023] [Indexed: 10/24/2023]
Abstract
Converting colloidal nanocrystals (NCs) into devices for various applications is facilitated by designing and controlling their surface properties. One key strategy for tailoring surface properties is thus to choose tailored surface ligands. In that context, amines have been universally used, with the goal to improve NCs synthesis, processing and performances. However, understanding the nature of surface sites in amine-capped NCs remains challenging, due to the complex surface compositions as well as surface ligands dynamic. Here, we investigate both surface sites and amine ligation in CdSe NCs by combining advanced NMR spectroscopy and computational modelling. Notably, dynamic nuclear polarization (DNP) enhanced 113 Cd and 77 Se 1D NMR helps to identify both bulk and surface sites of NCs, while 113 Cd 2D NMR spectroscopy enables to resolve amines terminated sites on both Se-rich and nonpolar surfaces. In addition to directly bonding to surface sites, amines are shown to also interact through hydrogen-bonding with absorbed water as revealed by 15 N NMR, augmented with computations. The characterization methodology developed for this work provides unique molecular-level insight into the surface sites of a range of amine-capped CdSe NCs, and paves the way to identify structure-function relationships and rational approaches towards colloidal NCs with tailored properties.
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Affiliation(s)
- Weicheng Cao
- Department of Chemistry and Applied Biosciences, ETH Zürich, 8093, Zürich, Switzerland
- Department of Chemistry, Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou, 310058, China
| | - Alexander Yakimov
- Department of Chemistry and Applied Biosciences, ETH Zürich, 8093, Zürich, Switzerland
| | - Xudong Qian
- Department of Chemistry, Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou, 310058, China
| | - Jiongzhao Li
- Department of Chemistry, Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou, 310058, China
| | - Xiaogang Peng
- Department of Chemistry, Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou, 310058, China
| | - Xueqian Kong
- Institute of Translational Medicine, Shanghai Jiao Tong University, Shanghai, 200240, China
- Department of Chemistry, Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou, 310058, China
| | - Christophe Copéret
- Department of Chemistry and Applied Biosciences, ETH Zürich, 8093, Zürich, Switzerland
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7
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Stam M, du Fossé I, Infante I, Houtepen AJ. Guilty as Charged: The Role of Undercoordinated Indium in Electron-Charged Indium Phosphide Quantum Dots. ACS NANO 2023; 17:18576-18583. [PMID: 37712414 PMCID: PMC10540256 DOI: 10.1021/acsnano.3c07029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 09/12/2023] [Indexed: 09/16/2023]
Abstract
Quantum dots (QDs) are known for their size-dependent optical properties, narrow emission bands, and high photoluminescence quantum yield (PLQY), which make them interesting candidates for optoelectronic applications. In particular, InP QDs are receiving a lot of attention since they are less toxic than other QD materials and are hence suitable for consumer applications. Most of these applications, such as LEDs, photovoltaics, and lasing, involve charging QDs with electrons and/or holes. However, charging of QDs is not easy nor innocent, and the effect of charging on the composition and properties of InP QDs is not yet well understood. This work provides theoretical insight into electron charging of the InP core and InP/ZnSe QDs. Density functional theory calculations are used to show that charging of InP-based QDs with electrons leads to the formation of trap states if the QD contains In atoms that are undercoordinated and thus have less than four bonds to neighboring atoms. InP core-only QDs have such atoms at the surface, which are responsible for the formation of trap states upon charging with electrons. We show that InP/ZnSe core-shell models with all In atoms fully coordinated can be charged with electrons without the formation of trap states. These results show that undercoordinated In atoms should be avoided at all times for QDs to be stably charged with electrons.
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Affiliation(s)
- Maarten Stam
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The
Netherlands
| | - Indy du Fossé
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The
Netherlands
| | - Ivan Infante
- BC
Materials, Basque Center for Materials, Applications, and Nanostructures, UPV/EHU Science Park, Leioa 48940, Spain
- Ikerbasque,
Basque Foundation for Science, Bilbao 48009, Spain
| | - Arjan J. Houtepen
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The
Netherlands
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8
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Bhati M, Ivanov SA, Senftle TP, Tretiak S, Ghosh D. How structural and vibrational features affect optoelectronic properties of non-stoichiometric quantum dots: computational insights. NANOSCALE 2023; 15:7176-7185. [PMID: 37013402 DOI: 10.1039/d2nr06785d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
While stoichiometric quantum dots (QDs) have been well studied, a significant knowledge gap remains in the atomistic understanding of the non-stoichiometric ones, which are predominantly present during the experimental synthesis. Here, we investigate the effect of thermal fluctuations on structural and vibrational properties of non-stoichiometric cadmium selenide (CdSe) nanoclusters: anion-rich (Se-rich) and cation-rich (Cd-rich) using ab initio molecular dynamics (AIMD) simulations. While the excess atoms on the surface fluctuate more for a given QD type, the optical phonon modes are mostly composed of Se atoms dynamics, irrespective of the composition. Moreover, Se-rich QDs have higher bandgap fluctuations compared to Cd-rich QDs, suggesting poor optical properties of Se-rich QDs. Additionally, non-adiabatic molecular dynamics (NAMD) suggests faster non-radiative recombination for Cd-rich QDs. Altogether, this work provides insights into the dynamic electronic properties of non-stoichiometric QDs and proposes a rationale for the observed optical stability and superiority of cation-rich candidates for light emission applications.
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Affiliation(s)
- Manav Bhati
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
- Department of Chemical and Biomolecular Engineering, Rice University, 6100 Main Street, Houston, TX 77005-1892, USA
| | - Sergei A Ivanov
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545, USA
- Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Thomas P Senftle
- Department of Chemical and Biomolecular Engineering, Rice University, 6100 Main Street, Houston, TX 77005-1892, USA
| | - Sergei Tretiak
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
- Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Dibyajyoti Ghosh
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
- Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
- Department of Materials Science and Engineering and Department of Chemistry, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110016, India
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9
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Yang RX, McCandler CA, Andriuc O, Siron M, Woods-Robinson R, Horton MK, Persson KA. Big Data in a Nano World: A Review on Computational, Data-Driven Design of Nanomaterials Structures, Properties, and Synthesis. ACS NANO 2022; 16:19873-19891. [PMID: 36378904 PMCID: PMC9798871 DOI: 10.1021/acsnano.2c08411] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Accepted: 11/08/2022] [Indexed: 05/30/2023]
Abstract
The recent rise of computational, data-driven research has significant potential to accelerate materials discovery. Automated workflows and materials databases are being rapidly developed, contributing to high-throughput data of bulk materials that are growing in quantity and complexity, allowing for correlation between structural-chemical features and functional properties. In contrast, computational data-driven approaches are still relatively rare for nanomaterials discovery due to the rapid scaling of computational cost for finite systems. However, the distinct behaviors at the nanoscale as compared to the parent bulk materials and the vast tunability space with respect to dimensionality and morphology motivate the development of data sets for nanometric materials. In this review, we discuss the recent progress in data-driven research in two aspects: functional materials design and guided synthesis, including commonly used metrics and approaches for designing materials properties and predicting synthesis routes. More importantly, we discuss the distinct behaviors of materials as a result of nanosizing and the implications for data-driven research. Finally, we share our perspectives on future directions for extending the current data-driven research into the nano realm.
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Affiliation(s)
- Ruo Xi Yang
- Materials
Science Division, Lawrence Berkeley National
Laboratory, Berkeley, California94720, United States
| | - Caitlin A. McCandler
- Materials
Science Division, Lawrence Berkeley National
Laboratory, Berkeley, California94720, United States
- Department
of Materials Science and Engineering, University
of California, Berkeley, California94720, United States
| | - Oxana Andriuc
- Department
of Chemistry, University of California, Berkeley, California94720, United States
- Liquid
Sunlight Alliance and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California94720, United States
| | - Martin Siron
- Materials
Science Division, Lawrence Berkeley National
Laboratory, Berkeley, California94720, United States
- Department
of Materials Science and Engineering, University
of California, Berkeley, California94720, United States
| | - Rachel Woods-Robinson
- Materials
Science Division, Lawrence Berkeley National
Laboratory, Berkeley, California94720, United States
| | - Matthew K. Horton
- Materials
Science Division, Lawrence Berkeley National
Laboratory, Berkeley, California94720, United States
- Department
of Materials Science and Engineering, University
of California, Berkeley, California94720, United States
| | - Kristin A. Persson
- Department
of Materials Science and Engineering, University
of California, Berkeley, California94720, United States
- Molecular
Foundry, Energy Sciences Area, Lawrence
Berkeley National Laboratory, Berkeley, California94720, United States
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10
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Geuchies JJ, Dijkhuizen R, Koel M, Grimaldi G, du Fossé I, Evers WH, Hens Z, Houtepen AJ. Zero-Threshold Optical Gain in Electrochemically Doped Nanoplatelets and the Physics Behind It. ACS NANO 2022; 16:18777-18788. [PMID: 36256901 PMCID: PMC9706803 DOI: 10.1021/acsnano.2c07519] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 10/13/2022] [Indexed: 06/07/2023]
Abstract
Colloidal nanoplatelets (NPLs) are promising materials for lasing applications. The properties are usually discussed in the framework of 2D materials, where strong excitonic effects dominate the optical properties near the band edge. At the same time, NPLs have finite lateral dimensions such that NPLs are not true extended 2D structures. Here we study the photophysics and gain properties of CdSe/CdS/ZnS core-shell-shell NPLs upon electrochemical n doping and optical excitation. Steady-state absorption and PL spectroscopy show that excitonic effects are weaker in core-shell-shell nanoplatelets due to the decreased exciton binding energy. Transient absorption studies reveal a gain threshold of only one excitation per nanoplatelet. Using electrochemical n doping, we observe the complete bleaching of the band edge exciton transitions. Combining electrochemical doping with transient absorption spectroscopy, we demonstrate that the gain threshold is fully removed over a broad spectral range and gain coefficients of several thousand cm-1 are obtained. These doped NPLs are the best performing colloidal nanomaterial gain medium reported to date, with the lowest gain threshold and broadest gain spectrum and gain coefficients that are 4 times higher than in n-doped colloidal quantum dots. The low exciton binding energy due to the CdS and ZnS shells, in combination with the relatively small lateral size of the NPLs, results in excited states that are effectively delocalized over the entire platelet. Core-shell NPLs are thus on the border between strong confinement in QDs and dominant Coulombic effects in 2D materials. We demonstrate that this limit is in effect ideal for optical gain and that it results in an optimal lateral size of the platelets where the gain threshold per nm2 is minimal.
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Affiliation(s)
- Jaco J. Geuchies
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2926 HZDelft, The Netherlands
| | - Robbert Dijkhuizen
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2926 HZDelft, The Netherlands
| | - Marijn Koel
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2926 HZDelft, The Netherlands
| | - Gianluca Grimaldi
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2926 HZDelft, The Netherlands
| | - Indy du Fossé
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2926 HZDelft, The Netherlands
| | - Wiel H. Evers
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2926 HZDelft, The Netherlands
| | - Zeger Hens
- Department
of Chemistry and Center for Nano and Biophotonics, Ghent University, 9000Ghent, Belgium
| | - Arjan J. Houtepen
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2926 HZDelft, The Netherlands
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11
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Ubbink R, Almeida G, Iziyi H, du Fossé I, Verkleij R, Ganapathy S, van Eck ERH, Houtepen AJ. A Water-Free In Situ HF Treatment for Ultrabright InP Quantum Dots. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2022; 34:10093-10103. [PMID: 36439318 PMCID: PMC9686131 DOI: 10.1021/acs.chemmater.2c02800] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 10/25/2022] [Indexed: 06/16/2023]
Abstract
Indium phosphide quantum dots are the main alternative for toxic and restricted Cd-based quantum dots for lighting and display applications, but in the absence of protecting ZnSe and/or ZnS shells, InP quantum dots suffer from low photoluminescence quantum yields. Traditionally, HF treatments have been used to improve the quantum yield of InP to ∼50%, but these treatments are dangerous and not well understood. Here, we develop a postsynthetic treatment that forms HF in situ from benzoyl fluoride, which can be used to strongly increase the quantum yield of InP core-only quantum dots. This treatment is water-free and can be performed safely. Simultaneous addition of the z-type ligand ZnCl2 increases the photoluminescence quantum yield up to 85%. Structural analysis via XPS as well as solid state and solution NMR measurements shows that the in situ generated HF leads to a surface passivation by indium fluoride z-type ligands and removes polyphosphates, but not PO3 and PO4 species from the InP surface. With DFT calculations it is shown that InP QDs can be trap-free even when PO3 and PO4 species are present on the surface. These results show that both polyphosphate removal and z-type passivation are necessary to obtain high quantum yields in InP core-only quantum dots. They further show that core-only InP QDs can achieve photoluminescence quantum yields rivalling those of InP/ZnSe/ZnS core/shell/shell QDs and the best core-only II-VI QDs.
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Affiliation(s)
- Reinout
F. Ubbink
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Guilherme Almeida
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Hodayfa Iziyi
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Indy du Fossé
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Ruud Verkleij
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Swapna Ganapathy
- Department
of Radiation Science and Technology, Faculty of Applied Sciences, Delft University of Technology, 2629 JB Delft, The Netherlands
| | - Ernst R. H. van Eck
- Magnetic
Resonance Research Center, Institute for Molecules and Materials, Radboud University, 6525 AJ Nijmegen, The Netherlands
| | - Arjan J. Houtepen
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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12
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Homer MK, Kuo DY, Dou FY, Cossairt BM. Photoinduced Charge Transfer from Quantum Dots Measured by Cyclic Voltammetry. J Am Chem Soc 2022; 144:14226-14234. [PMID: 35897128 DOI: 10.1021/jacs.2c04991] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Measuring and modulating charge-transfer processes at quantum dot interfaces are crucial steps in developing quantum dots as photocatalysts. In this work, cyclic voltammetry under illumination is demonstrated to measure the rate of photoinduced charge transfer from CdS quantum dots by directly probing the changing oxidation states of a library of molecular charge acceptors, including both hole and electron acceptors. The voltammetry data demonstrate the presence of long-lived charge donor states generated by native photodoping of the quantum dots as well as a positive correlation between driving force and rate of charge transfer. Changes to the voltammograms under illumination follow mechanistic predictions from the ErCi' zone diagram, and electrochemical modeling allows for measurement of the rate of productive electron transfer. Observed rates for photoinduced charge transfer are on the order of 0.1 s-1, which are distinct from the picosecond dynamics measured by conventional transient optical spectroscopy methods and are more closely connected to the quantum yield of light-mediated chemical transformations.
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Affiliation(s)
- Micaela K Homer
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | - Ding-Yuan Kuo
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | - Florence Y Dou
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | - Brandi M Cossairt
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
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13
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du Fossé I, Lal S, Hossaini AN, Infante I, Houtepen AJ. Effect of Ligands and Solvents on the Stability of Electron Charged CdSe Colloidal Quantum Dots. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2021; 125:23968-23975. [PMID: 34765075 PMCID: PMC8573769 DOI: 10.1021/acs.jpcc.1c07464] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 10/12/2021] [Indexed: 06/07/2023]
Abstract
Many colloidal quantum dot (QD)-based devices involve charging of the QD, either via intentional electronic doping or via electrical charge injection or photoexcitation. Previous research has shown that this charging can give rise to undesirable electrochemical surface reactions, leading to the formation of localized in-gap states. However, little is known about the factors that influence the stability of charged QDs against surface oxidation or reduction. Here, we use density functional theory to investigate the effect of various ligands and solvents on the reduction of surface Cd in negatively charged CdSe QDs. We find that X-type ligands can lead to significant shifts in the energy of the band edges but that the in-gap state related to reduced surface Cd is shifted in the same direction. As a result, shifting the band edges to higher energies does not necessarily lead to less stable electron charging. However, subtle changes in the local electrostatic environment lead to a clear correlation between the position of the in-gap state in the bandgap and the energy gained upon surface reduction. Binding ligands directly to the Cd sites most prone to reduction was found to greatly enhance the stability of the electron charged QDs. We find that ligands bind much more weakly after reduction of the Cd site, leading to a loss in binding energy that makes charge localization no longer energetically favorable. Lastly, we show that increasing the polarity of the solvent also increases the stability of QDs charged with electrons. These results highlight the complexity of surface reduction reactions in QDs and provide valuable strategies for improving the stability of charged QDs.
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Affiliation(s)
- Indy du Fossé
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Snigdha Lal
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Aydin Najl Hossaini
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Ivan Infante
- Department
of Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Arjan J. Houtepen
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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14
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Mulder J, du Fossé I, Alimoradi Jazi M, Manna L, Houtepen AJ. Electrochemical p-Doping of CsPbBr 3 Perovskite Nanocrystals. ACS ENERGY LETTERS 2021; 6:2519-2525. [PMID: 34307881 PMCID: PMC8294022 DOI: 10.1021/acsenergylett.1c00970] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 06/15/2021] [Indexed: 05/21/2023]
Abstract
Lead halide perovskite nanocrystals have drawn attention as active light-absorbing or -emitting materials for opto-electronic applications due to their facile synthesis, intrinsic defect tolerance, and color-pure emission ranging over the entire visible spectrum. To optimize their application in, e.g., solar cells and light-emitting diodes, it is desirable to gain control over electronic doping of these materials. However, predominantly due to the intrinsic instability of perovskites, successful electronic doping has remained elusive. Using spectro-electrochemistry and electrochemical transistor measurements, we demonstrate here that CsPbBr3 nanocrystals can be successfully and reversibly p-doped via electrochemical hole injection. From an applied potential of ∼0.9 V vs NHE, the emission quenches, the band edge absorbance bleaches, and the electronic conductivity quickly increases, demonstrating the successful injection of holes into the valence band of the CsPbBr3 nanocrystals.
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Affiliation(s)
- Jence
T. Mulder
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629HZ Delft, The Netherlands
| | - Indy du Fossé
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629HZ Delft, The Netherlands
| | - Maryam Alimoradi Jazi
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629HZ Delft, The Netherlands
| | - Liberato Manna
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629HZ Delft, The Netherlands
- Department
of Nanochemistry, Istituto Italiano di Tecnologia
(IIT), Via Morego 30, 16163 Genova, Italy
| | - Arjan J. Houtepen
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629HZ Delft, The Netherlands
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15
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Chen Y, Dorn RW, Hanrahan MP, Wei L, Blome-Fernández R, Medina-Gonzalez AM, Adamson MAS, Flintgruber AH, Vela J, Rossini AJ. Revealing the Surface Structure of CdSe Nanocrystals by Dynamic Nuclear Polarization-Enhanced 77Se and 113Cd Solid-State NMR Spectroscopy. J Am Chem Soc 2021; 143:8747-8760. [PMID: 34085812 DOI: 10.1021/jacs.1c03162] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Dynamic nuclear polarization (DNP) solid-state NMR (SSNMR) spectroscopy was used to obtain detailed surface structures of zinc blende CdSe nanocrystals (NCs) with plate or spheroidal morphologies which are capped by carboxylic acid ligands. 1D 113Cd and 77Se cross-polarization magic angle spinning (CPMAS) NMR spectra revealed distinct signals from Cd and Se atoms on the surface of the NCs, and those residing in bulk-like environments, below the surface. 113Cd cross-polarization magic-angle-turning (CP-MAT) experiments identified CdSe3O, CdSe2O2, and CdSeO3 Cd coordination environments on the surface of the NCs, where the oxygen atoms are presumably from coordinated carboxylate ligands. The sensitivity gain from DNP enabled natural isotopic abundance 2D homonuclear 113Cd-113Cd and 77Se-77Se and heteronuclear 113Cd-77Se scalar correlation solid-state NMR experiments which revealed the connectivity of the Cd and Se atoms. Importantly, 77Se{113Cd} scalar heteronuclear multiple quantum coherence (J-HMQC) experiments were used to selectively measure one-bond 77Se-113Cd scalar coupling constants (1J(77Se, 113Cd)). With knowledge of 1J(77Se, 113Cd), heteronuclear 77Se{113Cd} spin echo (J-resolved) NMR experiments were used to determine the number of Cd atoms bonded to Se atoms and vice versa. The J-resolved experiments directly confirmed that major Cd and Se surface species have CdSe2O2 and SeCd4 stoichiometries, respectively. Considering the crystal structure of zinc blende CdSe and the similarity of the solid-state NMR data for the platelets and spheroids, we conclude that the surface of the spheroidal CdSe NCs is primarily composed of {100} facets. The methods outlined here will generally be applicable to obtain detailed surface structures of various main group semiconductor nanoparticles.
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Affiliation(s)
- Yunhua Chen
- U.S. Department of Energy Ames Laboratory, Ames, Iowa 50011, United States.,Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Rick W Dorn
- U.S. Department of Energy Ames Laboratory, Ames, Iowa 50011, United States.,Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Michael P Hanrahan
- U.S. Department of Energy Ames Laboratory, Ames, Iowa 50011, United States.,Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Lin Wei
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | | | | | - Marquix A S Adamson
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Anne H Flintgruber
- U.S. Department of Energy Ames Laboratory, Ames, Iowa 50011, United States
| | - Javier Vela
- U.S. Department of Energy Ames Laboratory, Ames, Iowa 50011, United States.,Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Aaron J Rossini
- U.S. Department of Energy Ames Laboratory, Ames, Iowa 50011, United States.,Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
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16
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du Fossé I, Boehme SC, Infante I, Houtepen AJ. Dynamic Formation of Metal-Based Traps in Photoexcited Colloidal Quantum Dots and Their Relevance for Photoluminescence. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2021; 33:3349-3358. [PMID: 34054218 PMCID: PMC8154315 DOI: 10.1021/acs.chemmater.1c00561] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 04/09/2021] [Indexed: 05/11/2023]
Abstract
Trap states play a crucial role in the design of colloidal quantum dot (QD)-based technologies. The presence of these in-gap states can either significantly limit the efficiency of devices (e.g., in solar cells or LEDs) or play a pivotal role in the functioning of the technology (e.g., in catalysis). Understanding the atomistic nature of traps is therefore of the highest importance. Although the mechanism through which undercoordinated chalcogenide atoms can lead to trap states in II-VI QDs is generally well understood, the nature of metal-based traps remains more elusive. Previous research has shown that reduction of metal sites in negatively charged QDs can lead to in-gap states. Here, we use density functional theory to show that metal-based traps are also formed in charge-neutral but photoexcited CdSe QDs. It is found that Cd-Cd dimers and the concomitant trap states are transient in nature and appear and disappear on the picosecond time scale. Subsequent nonradiative recombination from the trap is shown to be much faster than radiative recombination, indicating that dimer-related trap states can quench the photoluminescence. These results are expected to be transferable to other II-VI materials and highlight the importance of surface redox reactions for the optical properties of QDs. Moreover, they show that photoexcitation can lead to atomic rearrangements on the surface and thus create transient in-gap states.
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Affiliation(s)
- Indy du Fossé
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Simon C. Boehme
- Laboratory
of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1, 8093 Zürich, Switzerland
- Empa-Swiss
Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland
| | - Ivan Infante
- Department
of Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Arjan J. Houtepen
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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17
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Steiner AM, Lissel F, Fery A, Lauth J, Scheele M. Perspektiven gekoppelter organisch‐anorganischer Nanostrukturen für Ladungs‐ und Energietransferanwendungen. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.201916402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Anja Maria Steiner
- Institut Physikalische Chemie und Physik der Polymere Leibniz-Institut für Polymerforschung Hohe Str. 6 01069 Dresden Deutschland
| | - Franziska Lissel
- Institut Makromolekulare Chemie Leibniz-Institut für Polymerforschung Hohe Str. 6 01069 Dresden Deutschland
- Technische Universität Dresden Mommsenstr. 4 01064 Dresden Deutschland
| | - Andreas Fery
- Institut Physikalische Chemie und Physik der Polymere Leibniz-Institut für Polymerforschung Hohe Str. 6 01069 Dresden Deutschland
- Technische Universität Dresden Mommsenstr. 4 01064 Dresden Deutschland
| | - Jannika Lauth
- Leibniz-Universität Hannover Institut für Physikalische Chemie und Elektrochemie Callinstr. 3A 30167 Hannover Deutschland
| | - Marcus Scheele
- Eberhard-Karls-Universität Tübingen Institut für Physikalische und Theoretische Chemie Auf der Morgenstelle 18 72076 Tübingen Deutschland
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18
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Steiner AM, Lissel F, Fery A, Lauth J, Scheele M. Prospects of Coupled Organic-Inorganic Nanostructures for Charge and Energy Transfer Applications. Angew Chem Int Ed Engl 2021; 60:1152-1175. [PMID: 32173981 PMCID: PMC7821299 DOI: 10.1002/anie.201916402] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Indexed: 12/20/2022]
Abstract
We review the field of organic-inorganic nanocomposites with a focus on materials that exhibit a significant degree of electronic coupling across the hybrid interface. These nanocomposites undergo a variety of charge and energy transfer processes, enabling optoelectronic applications in devices which exploit singlet fission, triplet energy harvesting, photon upconversion or hot charge carrier transfer. We discuss the physical chemistry of the most common organic and inorganic components. Based on those we derive synthesis and assembly strategies and design criteria on material and device level with a focus on photovoltaics, spin memories or optical upconverters. We conclude that future research in the field should be directed towards an improved understanding of the binding motif and molecular orientation at the hybrid interface.
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Affiliation(s)
- Anja Maria Steiner
- Institute for Physical Chemistry and Polymer PhysicsLeibniz Institute of Polymer ResearchHohe Str. 601069DresdenGermany
| | - Franziska Lissel
- Institute of Macromolecular ChemistryLeibniz Institute of Polymer ResearchHohe Str. 601069DresdenGermany
- Technische Universität DresdenMommsenstr. 401064DresdenGermany
| | - Andreas Fery
- Institute for Physical Chemistry and Polymer PhysicsLeibniz Institute of Polymer ResearchHohe Str. 601069DresdenGermany
- Technische Universität DresdenMommsenstr. 401064DresdenGermany
| | - Jannika Lauth
- Leibniz Universität HannoverInstitute of Physical Chemistry and ElectrochemistryCallinstr. 3A30167HannoverGermany
| | - Marcus Scheele
- Eberhard Karls-Universität TübingenInstitute of Physical and Theoretical ChemistryAuf der Morgenstelle 1872076TübingenGermany
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19
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Hartley CL, Kessler ML, Dempsey JL. Molecular-Level Insight into Semiconductor Nanocrystal Surfaces. J Am Chem Soc 2021; 143:1251-1266. [PMID: 33442974 DOI: 10.1021/jacs.0c10658] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Semiconductor nanocrystals exhibit attractive photophysical properties for use in a variety of applications. Advancing the efficiency of nanocrystal-based devices requires a deep understanding of the physical defects and electronic states that trap charge carriers. Many of these states reside at the nanocrystal surface, which acts as an interface between the semiconductor lattice and the molecular capping ligands. While a detailed structural and electronic understanding of the surface is required to optimize nanocrystal properties, these materials are at a technical disadvantage: unlike molecular structures, semiconductor nanocrystals lack a specific chemical formula and generally must be characterized as heterogeneous ensembles. Therefore, in order for the field to improve current nanocrystal-based technologies, a creative approach to gaining a "molecular-level" picture of nanocrystal surfaces is required. To this end, an expansive toolbox of experimental and computational techniques has emerged in recent years. In this Perspective, we critically evaluate the insight into surface structure and reactivity that can be gained from each of these techniques and demonstrate how their strategic combination is already advancing our molecular-level understanding of nanocrystal surface chemistry.
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Affiliation(s)
- Carolyn L Hartley
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, United States
| | - Melody L Kessler
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, United States
| | - Jillian L Dempsey
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, United States
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20
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Volk S, Yazdani N, Wood V. Manipulating Electronic Structure from the Bottom-Up: Colloidal Nanocrystal-Based Semiconductors. J Phys Chem Lett 2020; 11:9255-9264. [PMID: 32931296 DOI: 10.1021/acs.jpclett.0c01417] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Semiconductors assembled from colloidal nanocrystals (NCs) are often described in the same terms as their single-crystalline counterparts with references to conduction and valence band edges, doping densities, and electronic defects; however, how and why semiconductor properties manifest in these bottom-up fabricated thin films can be fundamentally different. In this Perspective, we describe the factors that determine the electronic structure in colloidal NC-based semiconductors, and comment on approaches for measuring or calculating this electronic structure. Finally, we discuss future directions for these semiconductors and highlight their potential to bridge the divide between localized quantum effects and long-range transport in thin films.
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Affiliation(s)
- Sebastian Volk
- Department of Information Technology and Electrical Engineering, ETH Zurich, Zurich, Switzerland 8092
| | - Nuri Yazdani
- Department of Information Technology and Electrical Engineering, ETH Zurich, Zurich, Switzerland 8092
| | - Vanessa Wood
- Department of Information Technology and Electrical Engineering, ETH Zurich, Zurich, Switzerland 8092
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21
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Morozov S, Pensa EL, Khan AH, Polovitsyn A, Cortés E, Maier SA, Vezzoli S, Moreels I, Sapienza R. Electrical control of single-photon emission in highly charged individual colloidal quantum dots. SCIENCE ADVANCES 2020; 6:6/38/eabb1821. [PMID: 32948584 PMCID: PMC7500932 DOI: 10.1126/sciadv.abb1821] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 07/27/2020] [Indexed: 05/30/2023]
Abstract
Electron transfer to an individual quantum dot promotes the formation of charged excitons with enhanced recombination pathways and reduced lifetimes. Excitons with only one or two extra charges have been observed and exploited for very efficient lasing or single-quantum dot light-emitting diodes. Here, by room-temperature time-resolved experiments on individual giant-shell CdSe/CdS quantum dots, we show the electrochemical formation of highly charged excitons containing more than 12 electrons and 1 hole. We report the control over intensity blinking, along with a deterministic manipulation of quantum dot photodynamics, with an observed 210-fold increase in the decay rate, accompanied by 12-fold decrease in the emission intensity, while preserving single-photon emission characteristics. These results pave the way for deterministic control over the charge state, and room-temperature decay rate engineering for colloidal quantum dot-based classical and quantum communication technologies.
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Affiliation(s)
- Sergii Morozov
- The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2BW, UK
| | - Evangelina L Pensa
- The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2BW, UK
| | - Ali Hossain Khan
- Department of Chemistry, Ghent University, Krijgslaan 281-S3, Gent 9000, Belgium
| | - Anatolii Polovitsyn
- Department of Chemistry, Ghent University, Krijgslaan 281-S3, Gent 9000, Belgium
| | - Emiliano Cortés
- Chair in Hybrid Nanosystems, Nano-Institute Munich, Faculty of Physics, Ludwig-Maxilimians-Universität München, München 80539, Germany
| | - Stefan A Maier
- The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2BW, UK
- Chair in Hybrid Nanosystems, Nano-Institute Munich, Faculty of Physics, Ludwig-Maxilimians-Universität München, München 80539, Germany
| | - Stefano Vezzoli
- The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2BW, UK
| | - Iwan Moreels
- Department of Chemistry, Ghent University, Krijgslaan 281-S3, Gent 9000, Belgium
| | - Riccardo Sapienza
- The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2BW, UK.
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22
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Volokh M, Mokari T. Metal/semiconductor interfaces in nanoscale objects: synthesis, emerging properties and applications of hybrid nanostructures. NANOSCALE ADVANCES 2020; 2:930-961. [PMID: 36133041 PMCID: PMC9418511 DOI: 10.1039/c9na00729f] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 02/04/2020] [Indexed: 05/11/2023]
Abstract
Hybrid nanostructures, composed of multi-component crystals of various shapes, sizes and compositions are much sought-after functional materials. Pairing the ability to tune each material separately and controllably combine two (or more) domains with defined spatial orientation results in new properties. In this review, we discuss the various synthetic mechanisms for the formation of hybrid nanostructures of various complexities containing at least one metal/semiconductor interface, with a focus on colloidal chemistry. Different synthetic approaches, alongside the underlying kinetic and thermodynamic principles are discussed, and future advancement prospects are evaluated. Furthermore, the proved unique properties are reviewed with emphasis on the connection between the synthetic method and the resulting physical, chemical and optical properties with applications in fields such as photocatalysis.
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Affiliation(s)
- Michael Volokh
- Department of Chemistry, Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev Beer-Sheva 8410501 Israel
| | - Taleb Mokari
- Department of Chemistry, Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev Beer-Sheva 8410501 Israel
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23
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Baturin V, Lepeshkin S, Bushlanova N, Uspenskii Y. Atomistic origins of charge traps in CdSe nanoclusters. Phys Chem Chem Phys 2020; 22:26299-26305. [PMID: 33175940 DOI: 10.1039/d0cp05139j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Constructing trap-free nanomaterials is a challenge that requires a fundamental understanding of the trapping phenomenon, especially the structural features responsible for electronic localization. Previously, such trapping configurations were explored by manual insertion of surface defects according to researchers' intuition, e.g. Cd-Se-Cd moiety [Houtepen et al., Chem. Mater., 2017, 29, 752]. In this study we report new types of traps in CdSe nanoclusters, including the metal-based one, which were found using a novel, unbiased approach. Namely, we screened a vast number of globally optimized CdnSem clusters (n,m ≤ 15) for localized electronic states. These systems model the wide diversity of defects in unpassivated areas of a nanocluster surface, while still being accessible for ab initio global optimization. Despite this variety, all 39 traps we found fall into 3 types, including two new ones. Such a reduction shows the universal character of discovered traps, irrelevant to the global structure of a cluster. Many of these traps not only have newly reported atomic arrangements, but also original confinement mechanisms which are explained at the atomistic level. We found that the relaxation and global optimization of the cluster structure greatly reduce the number of traps and push the trap energies from midgap to the near-gap edge positions, which agrees with the spectral measurements of II-VI semiconductor nanocrystals.
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Affiliation(s)
- Vladimir Baturin
- Skolkovo Institute of Science and Technology, Bolshoy Boulevard 30, bld. 1, Moscow 121205, Russia.
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24
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Grimaldi G, van den Brom MJ, du Fossé I, Crisp RW, Kirkwood N, Gudjonsdottir S, Geuchies JJ, Kinge S, Siebbeles LDA, Houtepen AJ. Engineering the Band Alignment in QD Heterojunction Films via Ligand Exchange. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2019; 123:29599-29608. [PMID: 31867087 PMCID: PMC6913897 DOI: 10.1021/acs.jpcc.9b09470] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 11/18/2019] [Indexed: 05/24/2023]
Abstract
Colloidal quantum dots (QDs) allow great flexibility in the design of optoelectronic devices, thanks to their size-dependent optical and electronic properties and the possibility to fabricate thin films with solution-based processing. In particular, in QD-based heterojunctions, the band gap of both components can be controlled by varying the size of the QDs. However, control over the band alignment between the two materials is required to tune the dynamics of carrier transfer across a heterostructure. We demonstrate that ligand exchange strategies can be used to control the band alignment of PbSe and CdSe QDs in a mixed QD solid, shifting it from a type-I to a type-II alignment. The change in alignment is observed in both spectroelectrochemical and transient absorption measurements, leading to a change in the energy of the conduction band edges in the two materials and in the direction of electron transfer upon photoexcitation. Our work demonstrates the possibility to tune the band offset of QD heterostructures via control of the chemical species passivating the QD surface, allowing full control over the energetics of the heterostructure without requiring changes in the QD composition.
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Affiliation(s)
- Gianluca Grimaldi
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Mark J. van den Brom
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Indy du Fossé
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Ryan W. Crisp
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Nicholas Kirkwood
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Solrun Gudjonsdottir
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Jaco J. Geuchies
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Sachin Kinge
- Toyota
Motor Europe, Materials Research & Development, Hoge Wei 33, B-1930 Zaventem, Belgium
| | - Laurens D. A. Siebbeles
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Arjan J. Houtepen
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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25
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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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26
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Gudjonsdottir S, Koopman C, Houtepen AJ. Enhancing the stability of the electron density in electrochemically doped ZnO quantum dots. J Chem Phys 2019; 151:144708. [DOI: 10.1063/1.5124534] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Solrun Gudjonsdottir
- Chemical Engineering, Optoelectronic Materials, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Christel Koopman
- Chemical Engineering, Optoelectronic Materials, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Arjan J. Houtepen
- Chemical Engineering, Optoelectronic Materials, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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27
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Gudjonsdottir S, van der Stam W, Koopman C, Kwakkenbos B, Evers WH, Houtepen AJ. On the Stability of Permanent Electrochemical Doping of Quantum Dot, Fullerene, and Conductive Polymer Films in Frozen Electrolytes for Use in Semiconductor Devices. ACS APPLIED NANO MATERIALS 2019; 2:4900-4909. [PMID: 31475245 PMCID: PMC6711363 DOI: 10.1021/acsanm.9b00863] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Accepted: 07/16/2019] [Indexed: 05/03/2023]
Abstract
Semiconductor films that allow facile ion transport can be electronically doped via electrochemistry, where the amount of injected charge can be controlled by the potential applied. To apply electrochemical doping to the design of semiconductor devices, the injected charge has to be stabilized to avoid unintentional relaxation back to the intrinsic state. Here, we investigate methods to increase the stability of electrochemically injected charges in thin films of a wide variety of semiconductor materials, namely inorganic semiconductors (ZnO NCs, CdSe NCs, and CdSe/CdS core/shell NCs) and organic semiconductors (P3DT, PCBM, and C60). We show that by charging the semiconductors at elevated temperatures in solvents with melting points above room temperature, the charge stability at room temperature increases greatly, from seconds to days. At reduced temperature (-75 °C when using succinonitrile as electrolyte solvent) the injected charge becomes entirely stable on the time scale of our experiments (up to several days). Other high melting point solvents such as dimethyl sulfone, ethylene carbonate, and poly(ethylene glycol) (PEG) also offer increased charge stability at room temperature. Especially the use of PEG increases the room temperature charge stability by several orders of magnitude compared to using acetonitrile. We discuss how this improvement of the charge stability is related to the immobilization of electrolyte ions and impurities. While the electrolyte ions are immobilized, conductivity measurements show that electrons in the semiconductor films remain mobile. These results highlight the potential of using solidified electrolytes to stabilize injected charges, which is a promising step toward making semiconductor devices based on electrochemically doped semiconductor thin films.
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Affiliation(s)
- Solrun Gudjonsdottir
- Chemical
Engineering, Optoelectronic Materials, and Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Ward van der Stam
- Chemical
Engineering, Optoelectronic Materials, and Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Christel Koopman
- Chemical
Engineering, Optoelectronic Materials, and Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Bob Kwakkenbos
- Chemical
Engineering, Optoelectronic Materials, and Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Wiel H. Evers
- Chemical
Engineering, Optoelectronic Materials, and Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Arjan J. Houtepen
- Chemical
Engineering, Optoelectronic Materials, and Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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