| 1. |
- Chen, Wei, et al.
(författare)
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Colloidal PbS quantum dot stacking kinetics during deposition via printing
- 2020
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Ingår i: Nanoscale Horizons. - : Royal Society of Chemistry (RSC). - 2055-6764 .- 2055-6756. ; 5:5, s. 880-885
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Tidskriftsartikel (refereegranskat)abstract
- Colloidal PbS quantum dots (QDs) are attractive for solution-processed thin-film optoelectronic applications. In particular, directly achieving QD thin-films by printing is a very promising method for low-cost and large-scale fabrication. The kinetics of QD particles during the deposition process play an important role in the QD film quality and their respective optoelectronic performance. In this work, the particle self-organization behavior of small-sized QDs with an average diameter of 2.88 +/- 0.36 nm is investigated for the first time in situ during printing by grazing-incidence small-angle X-ray scattering (GISAXS). The time-dependent changes in peak intensities suggest that the structure formation and phase transition of QD films happen within 30 seconds. The stacking of QDs is initialized by a templating effect, and a face-centered cubic (FCC) film forms in which a superlattice distortion is also found. A body-centered cubic nested FCC stacking is the final QD assembly layout. The small size of the inorganic QDs and the ligand collapse during the solvent evaporation can well explain this stacking behavior. These results provide important fundamental understanding of structure formation of small-sized QD based films prepared via large-scale deposition with printing with a slot die coater.
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| 2. |
- Chen, Wei, et al.
(författare)
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In situ Grazing-Incidence Small-Angle X-ray Scattering Observation of Gold Sputter Deposition on a PbS Quantum Dot Solid
- 2020
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Ingår i: ACS Applied Materials and Interfaces. - : NLM (Medline). - 1944-8244 .- 1944-8252. ; 12:41, s. 46942-46952
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Tidskriftsartikel (refereegranskat)abstract
- For PbS quantum dot (QD)-based optoelectronic devices, gold is the most frequently used electrode material. In most device architectures, gold is in direct contact with the QD solid. To better understand the formation of the interface between gold and a close-packed QD layer at an early stage, in situ grazing-incidence small-angle X-ray scattering is used to observe the gold sputter deposition on a 1,2-ethanedithiol (EDT)-treated PbS QD solid. In the kinetics of gold layer growth, the forming and merging of small gold clusters (radius less than 1.6 nm) are observed at the early stages. The thereby formed medium gold clusters (radius between 1.9-2.4 nm) are influenced by the QDs' templating effect. Furthermore, simulations suggest that the medium gold clusters grow preferably along the QDs' boundaries rather than as a top coating of the QDs. When the thickness of the sputtered gold layer reaches 6.25 nm, larger gold clusters with a radius of 5.3 nm form. Simultaneously, a percolation layer with a thickness of 2.5 nm is established underneath the gold clusters. This fundamental understanding of the QD-gold interface formation will help to control the implementation of sputtered gold electrodes on close-packed QD solids in device manufacturing processes.
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| 3. |
- Guan, Tianfu, et al.
(författare)
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Decoding the Self-Assembly Plasmonic Interface Structure in a PbS Colloidal Quantum Dot Solid for a Photodetector
- 2023
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 17:22, s. 23010-23019
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid plasmonic nanostructures have gained enormous attention in a variety of optoelectronic devices due to their surface plasmon resonance properties. Self-assembled hybrid metal/quantum dot (QD) architectures offer a means of coupling the properties of plasmonics and QDs to photodetectors, thereby modifying their functionality. The arrangement and localization of hybrid nanostructures have an impact on exciton trapping and light harvesting. Here, we present a hybrid structure consisting of self-assembled gold nanospheres (Au NSs) embedded in a solid matrix of PbS QDs for mapping the interface structures and the motion of charge carriers. Grazing-incidence small-angle X-ray scattering is utilized to analyze the localization and spacing of the Au NSs within the hybrid structure. Furthermore, by correlating the morphology of the Au NSs in the hybrid structure with the corresponding differences observed in the performance of photodetectors, we are able to determine the impact of interface charge carrier dynamics in the coupling structure. From the perspective of architecture, our study provides insights into the performance improvement of optoelectronic devices.
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| 4. |
- Jiang, Xinyu, et al.
(författare)
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Internal nanoscale architecture and charge carrier dynamics of wide bandgap non-fullerene bulk heterojunction active layers in organic solar cells
- 2020
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 8:44, s. 23628-23636
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Tidskriftsartikel (refereegranskat)abstract
- Bulk heterojunction (BHJ) organic solar cells have gained increasing attention in the past few years. In this work, active layers of a wide-bandgap polymer donor with benzodithiophene units PBDB-T-2F and a non-fullerene small molecule acceptor IT-M are assembled into photovoltaic devices with different amounts of solvent additive 1,8-diiodooctane (DIO). The influence of DIO on the nanoscale film morphology and crystalline structure as well as the charge carrier dynamics of the active layers are investigated by combining grazing-incidence small-angle X-ray scattering (GISAXS), grazing-incidence wide-angle X-ray scattering (GIWAXS), X-ray reflectivity (XRR), UV-visible (UV-vis) absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), time-resolved photoluminescence (TRPL) and space charge limited current measurements, which are correlated with the corresponding performance of the solar cells. At 0.5 vol% DIO addition, the wide-bandgap non-fullerene organic solar cells show the best performance due to high open-circuit voltage and short-circuit current resulting from an improved charge carrier management due to the optimal inner nanoscale morphology of the active layers in terms of surface enrichment, crystallinity and crystalline orientation.
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| 5. |
- Shen, Hangjia, et al.
(författare)
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Atomically FeN2 moieties dispersed on mesoporous carbon : A new atomic catalyst for efficient oxygen reduction catalysis
- 2017
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Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855 .- 2211-3282. ; 35, s. 9-16
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Tidskriftsartikel (refereegranskat)abstract
- Earth-abundant materials with Fe-N-C centers have been identified as promising catalysts for oxygen reduction reaction (ORR), but these alternatives for Pt catalysts are usually the porphyrin-like FeN4 configuration. The density functional theory (DFT) calculations reveal that FeN2 outperforms FeN4 due to its lower interaction with *O-2 and *OH intermediates and enhanced electron transport, however, achieving an optimum design of these earth-abundant materials with the enriched FeN2 catalytic centers is still a great challenge. Here, we report an intriguing template casting strategy to introduce a mass of atomically dispersed FeN2 moieties onto the surface of N-doped ordered mesoporous carbon for boosting ORR electrocatalysis. One of unique parts herein is to pre anchor Fe precursor on the surface of template (SBA-15) during catalyst synthesis, preventing Fe from penetrating into the carbon skeleton and facilitating the removal of excessive Fe-based particles during silica elimination by HF etching, resulting in a desirable model structure comprising only highly active atomically dispersed FeN2 sites, as confirmed by high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM), extended X-ray absorption fine structure (EXAFS) and Mossbauer spectroscopy analysis. The well-defined structure prompts us to understand the nature of the catalytic active sites, and to demonstrate that the catalyst activity is linearly proportional to the concentration of FeN2 sites. The obtained atomic electrocatalyst exhibits superior electrocatalytic performance for ORR with a more positive half-wave potential than that of Pt/C catalyst. We further establish a kinetic model to predict the ORR activity of these single-atom dispersed catalysts. The present work elaborates on a profound understanding for designing low-cost, highly efficient FeN2-based electrocatalyst for boosting ORR.
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