ORCID Profile
0000-0003-1070-5859
Current Organisation
University of Sydney
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Optical Properties of Materials | Physical Chemistry of Materials | Nanotechnology | Macromolecular and Materials Chemistry | Organic Semiconductors | Molecular and Organic Electronics | Theory and Design of Materials | Transport Properties and Non-Equilibrium Processes | Structural Chemistry and Spectroscopy
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in the Physical Sciences | Solar-Photovoltaic Energy | Expanding Knowledge in the Biological Sciences |
Related Links
Publications
Solution-Processed Faraday Rotators Using Single Crystal Lead Halide Perovskites
Publisher: Wiley
Date: 13-02-2020
Observation of oxygen vacancy migration in memory devices based on ZnO nanoparticles
Publisher: AIP Publishing
Date: 11-04-2017
DOI: 10.1063/1.4979973
Abstract: We investigate the mechanism of resistive switching in non-volatile memory devices based on an ITO/ZnO nanoparticles/Al structure using electroabsorption (EA) spectroscopy and X-ray photoelectron spectroscopy (XPS). By incorporating a small amount of low-bandgap organic semiconductor, poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT), as a probe molecule for EA characterization, we study the change in the built-in potential during the switching process under different ambient conditions. We compare the concentrations of oxygen vacancies between the Al/ZnO interface and the bulk of the ZnO nanoparticle film by XPS. We also investigate the effect of an external electrical field on the concentration of oxygen vacancies at the Al/ZnO interface. We find that the resistive switching can be attributed to the migration of oxygen vacancies driven by the electrical field, accompanied by adsorption/desorption of oxygen molecules at the Al/ZnO interface. This process gives rise to the formation of a dipole layer, which modulates the injection barrier, and is responsible for switching the resistance state of the memory device.
β Phase in Chiral Polyfluorene Forms via a Precursor
Publisher: American Chemical Society (ACS)
Date: 04-05-2009
DOI: 10.1021/MA900031U
The chiroptical properties of chiral substituted poly[3-((3S)-3,7-dimethyloctyl)thiophene] as a function of film thickness
Publisher: Elsevier BV
Date: 04-2007
Sub-4 nm mapping of donor–acceptor organic semiconductor nanoparticle composition
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3NR00839H
Abstract: The first report of sub-4 nm mapping of donor : acceptor nanoparticle composition in eco-friendly colloidal dispersions for organic electronics.
Molecular Energy Transfer under the Strong Light–Matter Interaction Regime
Publisher: American Chemical Society (ACS)
Date: 30-05-2023
Magnetic optical rotary dispersion and magnetic circular dichroism in methylammonium lead halide perovskites
Publisher: Wiley
Date: 31-08-2021
DOI: 10.1002/CHIR.23346
Abstract: Large magnetic optical rotary dispersion (Faraday rotation) has been demonstrated recently in methylammonium lead bromide. Here, we investigate the prospect of extending the active spectral range by altering the halogen. We also investigate the origins of large Faraday rotation in these diamagnetic materials using magnetic circular dichroism (MCD) spectroscopy and the Kramers–Kronig relations. We find that, while MAPbCl 3 (MA = methylammonium) single crystals exhibit a large Verdet constant in the blue, no appreciable Faraday rotation is observed in the red/near infra‐red for MAPbI 3 single crystals. However, in all film s les, we find clear evidence of large MCD resulting from the Zeeman splitting of the highly resonant 1s exciton state. Our Kramers–Kronig calculations of Faraday rotation based on MCD data matches well with the dispersion of our experimental data for MAPbCl 3 and MAPbBr 3 , with some deviation in magnitude—demonstrating the excitonic nature of Faraday rotation in these materials. However, our calculations predict significant Faraday rotation in MAPbI 3 , contrary to our experimental results, indicating a potential discrepancy between the properties of the thin film and single crystal.
Probing the switching mechanism in ZnO nanoparticle memristors
Publisher: AIP Publishing
Date: 15-09-2014
DOI: 10.1063/1.4894823
Abstract: We investigate the resistance switching mechanism in memristors based on colloidal ZnO nanoparticles using electroabsorption (EA) spectroscopy. In this EA experiment, we incorporate a small amount of low-bandgap polymer, poly(9,9-dioctylfluorene-co-benzothiadiazole), as a probe molecule in ZnO-nanoparticle memristors. By characterizing this polymer, we can study the change of built-in potential (VBI) in the device during the resistance switching process without disturbing the resistance state by the EA probe light. Our results show that VBI increases when the device is switched to the high resistance state, suggesting a shift of effective workfunction of the electrode. Thus, we attribute the resistance switching to the field-dependent migration of oxygen vacancies associated with the adsorption and desorption of oxygen molecules at the Al/ZnO interface. This process results in the modulation of the interfacial injection barrier, which governs the resistance state of the device.
Achromatic polarization control in the visible
Publisher: Springer Science and Business Media LLC
Date: 27-10-2021
Molecularly isolated perylene diimides enable both strong exciton–photon coupling and high photoluminescence quantum yield
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9TC00093C
Abstract: Sterically hindered perylene diimides allow substantial Rabi splitting ( i.e. strong exciton–photon coupling) while maintaining up to 85% photoluminescence quantum yield.
The Role of Fiber Agglomeration in Formation of Perylene-Based Fiber Networks
Publisher: Elsevier BV
Date: 08-2020
Reflection of light by anisotropic molecular crystals including exciton-polaritons and spatial dispersion
Publisher: AIP Publishing
Date: 17-11-2016
DOI: 10.1063/1.4967404
Abstract: A theory for the reflection of light by molecular crystals is described, which reproduces the minimum within the reflection band that is observed experimentally. The minimum in reflection is related to the excitation of polaritons in the crystal. The theory involves reformulation of the boundary conditions for electromagnetic waves at the interface between vacuum and material. The material is modeled by a cubic lattice of oriented Lorentz oscillators. By requiring uniformity of gauge of the electromagnetic potential across the interface between vacuum and the dipole lattice, the need for additional boundary conditions is obviated. The frequency separation between the maxima in reflectance on both sides of the minimum allows for the extraction of a plasma frequency. The plasma frequencies extracted from reflection spectra are compared to the plasma frequencies calculated directly from structural data on the crystals and the oscillator strengths of the constituent molecules. A good agreement between extracted and calculated plasma frequency is obtained for a set of 11 dye molecules.
Large Photoinduced Circular Dichroism in Chiral Polyfluorene
Publisher: American Chemical Society (ACS)
Date: 18-09-2009
DOI: 10.1021/JP9072526
Abstract: At 77 K, thermally annealed films of chiral poly[9,9-bis((3S)-3,7-dimethyloctyl)-2,7-fluorene] show a photoinduced absorption (PIA) band near 1.5 eV due to a transition from the lowest triplet state to a higher triplet state. This photoinduced absorption is found to show circular dichroism (CD). Dividing this CD by the magnitude of the PIA, we find that the selectivity for absorption of left circular polarized light over right circularly polarized light is remarkably high and characterized by a dissymmetry ratio g = +0.2. The unusual magnitude of g is interpreted as arising from extrinsic CD, i.e., from the interaction of the local linear polarization of the triplet-triplet absorption with the linear birefringence of the surrounding polymer matrix.
Chiral-perovskite optoelectronics
Publisher: Springer Science and Business Media LLC
Date: 10-03-2020
Theoretical Prediction of Chiral 3D Hybrid Organic–Inorganic Perovskites
Publisher: Wiley
Date: 15-03-2019
Abstract: Hybrid organic–inorganic perovskites (HOIPs), in particular 3D HOIPs, have demonstrated remarkable properties, including ultralong charge‐carrier diffusion lengths, high dielectric constants, low trap densities, tunable absorption and emission wavelengths, strong spin–orbit coupling, and large Rashba splitting. These superior properties have generated intensive research interest in HOIPs for high‐performance optoelectronics and spintronics. Here, 3D hybrid organic–inorganic perovskites that implant chirality through introducing the chiral methylammonium cation are demonstrated. Based on structural optimization, phonon spectra, formation energy, and ab initio molecular dynamics simulations, it is found that the chirality of the chiral cations can be successfully transferred to the framework of 3D HOIPs, and the resulting 3D chiral HOIPs are both kinetically and thermodynamically stable. Combining chirality with the impressive optical, electrical, and spintronic properties of 3D perovskites, 3D chiral perovskites is of great interest in the fields of piezoelectricity, pyroelectricity, ferroelectricity, topological quantum engineering, circularly polarized optoelectronics, and spintronics.
Conformational Effect on Energy Transfer in Single Polythiophene Chains
Publisher: American Chemical Society (ACS)
Date: 03-08-2012
DOI: 10.1021/JP306674T
Abstract: Herein we describe the use of regioregular (rr-) and regiorandom (rra-) P3HT as models to study energy transfer in ordered and disordered single conjugated polymer chains. Single molecule fluorescence spectra and excitation/emission polarization measurements were compared with a Förster resonance energy transfer (FRET) model simulation. An increase in the mean single chain polarization anisotropy from excitation to emission was observed for both rr- and rra-P3HT. The peak emission wavelengths of rr-P3HT were at substantially lower energies than those of rra-P3HT. A simulation based on FRET in single polymer chain conformations successfully reproduced the experimental observations. These studies showed that ordered conformations facilitated efficient energy transfer to a small number of low-energy sites compared to disordered conformations. As a result, the histograms of spectral peak wavelengths for ordered conformations were centered at much lower energies than those obtained for disordered conformations. Collectively, these experimental and simulated results provide the basis for quantitatively describing energy transfer in an important class of conjugated polymers commonly used in a variety of organic electronics applications.
Multi-resonance TADF in optical cavities: suppressing excimer emission through efficient energy transfer to the lower polariton states
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3TC02133E
Site-selective photocatalytic functionalization of peptides and proteins at selenocysteine
Publisher: Springer Science and Business Media LLC
Date: 12-11-2022
DOI: 10.1038/S41467-022-34530-Z
Abstract: The importance of modified peptides and proteins for applications in drug discovery, and for illuminating biological processes at the molecular level, is fueling a demand for efficient methods that facilitate the precise modification of these biomolecules. Herein, we describe the development of a photocatalytic method for the rapid and efficient dimerization and site-specific functionalization of peptide and protein diselenides. This methodology, dubbed the photocatalytic diselenide contraction, involves irradiation at 450 nm in the presence of an iridium photocatalyst and a phosphine and results in rapid and clean conversion of diselenides to reductively stable selenoethers. A mechanism for this photocatalytic transformation is proposed, which is supported by photoluminescence spectroscopy and density functional theory calculations. The utility of the photocatalytic diselenide contraction transformation is highlighted through the dimerization of selenopeptides, and by the generation of two families of protein conjugates via the site-selective modification of calmodulin containing the 21 st amino acid selenocysteine, and the C-terminal modification of a ubiquitin diselenide.
Probing Through-Bond and Through-Space Interactions in Singlet Fission-Based Pentacene Dimers
Publisher: American Chemical Society (ACS)
Date: 23-09-2022
DOI: 10.1021/ACS.JPCLETT.2C02061
Abstract: Interchromophoric interactions such as Coulombic coupling and exchange interactions are crucial to the functional properties of numerous π-conjugated systems. Here, we use magnetic circular dichroism (MCD) spectroscopy to investigate interchromophoric interactions in singlet fission relevant pentacene dimers. Using a simple analytical model, we outline a general relationship between the geometry of pentacene dimers and their calculated MCD response. We analyze experimental MCD spectra of different covalently bridged pentacene dimers to reveal how the molecular structure of the "bridge" affects the magnitude of through-space Coulombic and through-bond exchange interactions in the system. Our results show that through-bond interactions are significant in dimers with conjugated molecules as bridging units and these interactions promote the overall electronic coupling in the system. Our generalized approach paves the way for the application of MCD in investigating interchromophoric interactions across a range of π-conjugated systems.
Fine Structure and Spin Dynamics of Linearly Polarized Indirect Excitons in Two-Dimensional CdSe/CdTe Colloidal Heterostructures
Publisher: American Chemical Society (ACS)
Date: 06-09-2019
Abstract: Heterostructured two-dimensional colloidal nanoplatelets are a class of material that has attracted great interest for optoelectronic applications due to their high photoluminescence yield, atomically tunable thickness, and ultralow lasing thresholds. Of particular interest are laterally heterostructured core-crown nanoplatelets with a type-II band alignment, where the in-plane spatial separation of carriers leads to indirect (or charge transfer) excitons with long lifetimes and bright, highly Stokes shifted emission. Despite this, little is known about the nature of the lowest energy exciton states responsible for emission in these materials. Here, using polarization-controlled, steady-state, and time-resolved photoluminescence measurements, at temperatures down to 1.6 K and magnetic fields up to 30 T, we study the exciton fine structure and spin dynamics of archetypal type-II CdSe/CdTe core-crown nanoplatelets. Complemented by theoretical modeling and zero-field quantum beat measurements, we find the bright-exciton fine structure consists of two linearly polarized states with a fine structure splitting ∼50 μeV and an indirect exciton Landé
Circular Differential Scattering of Light in Films of Chiral Polyfluorene
Publisher: American Chemical Society (ACS)
Date: 19-04-2007
DOI: 10.1021/JP067852R
Abstract: Circular differential transmission in thick films (1.1 mum) of poly{9,9-bis[(3S)-3,7-dimethyloctyl]-2,7-fluorene} is investigated. The vitrified liquid crystalline film obtained after annealing shows high circular differential transmission of light in the wavelength range where the polyfluorene does not absorb (lambda > 450 nm). Using a specifically designed chiroptical setup, we show that circular selective reflection of light in which the circular polarization of the light is retained after reflection, a process which is characteristic for cholesteric liquid crystalline films, makes a negligible contribution to the differential transmission. Using an integrating sphere, we show that circular differential scattering can account for the observed circular differential transmission for lambda > 450 nm.
Circular Selective Reflection of Light Proving Cholesteric Ordering in Thin Layers of Chiral Fluorene Polymers
Publisher: American Chemical Society (ACS)
Date: 03-06-2011
DOI: 10.1021/JZ200500A
Pentacene-Bridge Interactions in an Axially Chiral Binaphthyl Pentacene Dimer
Publisher: American Chemical Society (ACS)
Date: 16-08-2021
Probing Charge Carrier Density in a Layer of Photodoped ZnO Nanoparticles by Spectroscopic Ellipsometry
Publisher: American Chemical Society (ACS)
Date: 18-08-2010
DOI: 10.1021/JP104846H
Free charge photogeneration in a single component high photovoltaic efficiency organic semiconductor
Publisher: Springer Science and Business Media LLC
Date: 20-05-2022
DOI: 10.1038/S41467-022-30127-8
Abstract: Organic photovoltaics (OPVs) promise cheap and flexible solar energy. Whereas light generates free charges in silicon photovoltaics, excitons are normally formed in organic semiconductors due to their low dielectric constants, and require molecular heterojunctions to split into charges. Recent record efficiency OPVs utilise the small molecule, Y6, and its analogues, which – unlike previous organic semiconductors – have low band-gaps and high dielectric constants. We show that, in Y6 films, these factors lead to intrinsic free charge generation without a heterojunction. Intensity-dependent spectroscopy reveals that 60–90% of excitons form free charges at AM1.5 light intensity. Bimolecular recombination, and hole traps constrain single component Y6 photovoltaics to low efficiencies, but recombination is reduced by small quantities of donor. Quantum-chemical calculations reveal strong coupling between exciton and CT states, and an intermolecular polarisation pattern that drives exciton dissociation. Our results challenge how current OPVs operate, and renew the possibility of efficient single-component OPVs.
Organic polariton lasing with molecularly isolated perylene diimides
Publisher: AIP Publishing
Date: 27-07-2020
DOI: 10.1063/5.0012461
Abstract: A dye immersed in a polymer matrix represents a promising material class for organic polariton lasers. While polariton condensation has been established for boron-dipyrromethene blends, it has yet to be extended to other small dye blends. Here, we demonstrate polariton lasing in a molecularly isolated perylene diimide immersed in polystyrene. The emission exhibits threshold behavior, strong directionality, and slight blueshifting of organic polariton systems. We expect that continuous exploration of new dyes will allow improved performance in organic polariton lasing.
Improved optical confinement in ambipolar field-effect transistors toward electrical injection organic lasers
Publisher: AIP Publishing
Date: 18-10-2021
DOI: 10.1063/5.0063336
Abstract: Increasing optical confinement is critical to lowering laser thresholds and increasing modal gain in semiconductor lasers. Here, mode-solver calculations are used to demonstrate that improvements to optical confinement are possible in organic field-effect transistor geometries by using high refractive index cladding layers. Optical experiments show that the proposed structure increases the efficiency of lified spontaneous emission (ASE) and lowers ASE thresholds without incurring additional losses. The results suggest that the structure can be used to improve optical confinement for both optically pumped and electrical injection organic lasers where thin, low refractive index active materials are required.
Interface limited charge extraction and recombination in organic photovoltaics
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4EE00665H
Emission Decay Pathways Sensitive to Circular Polarization of Excitation
Publisher: American Chemical Society (ACS)
Date: 24-09-2018
Bimolecular Recombination in Organic Photovoltaics
Publisher: Annual Reviews
Date: 04-2014
DOI: 10.1146/ANNUREV-PHYSCHEM-040513-103615
Abstract: The recombination of electrons and holes is a major loss mechanism in photovoltaic devices that controls their performance. We review scientific literature on bimolecular recombination (BR) in bulk heterojunction organic photovoltaic devices to bring forward existing ideas on the origin and nature of BR and highlight both experimental and theoretical work done to quantify its extent. For these systems, Langevin theory fails to explain BR, and recombination dynamics turns out to be dependent on mobility, temperature, electric field, charge carrier concentration, and trapped charges. Relationships among the photocurrent, open-circuit voltage, fill factor, and morphology are discussed. Finally, we highlight the recent emergence of a molecular-level picture of recombination, taking into account the spin and delocalization of charges. Together with the macroscopic picture of recombination, these new insights allow for a comprehensive understanding of BR and provide design principles for future materials and devices.
Emission State Structure and Linewidth Broadening Mechanisms in Type-II CdSe/CdTe Core–Crown Nanoplatelets: A Combined Theoretical–Single Nanocrystal Optical Study
Publisher: American Chemical Society (ACS)
Date: 10-07-2020
Chiral metal–organic frameworks for photonics
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2CS00129B
Abstract: This review explores recent progress in the use of chiral metal–organic frameworks (MOFs) as platforms for circularly polarised luminescence (CPL), chiroptical switching, and second-order nonlinear optics (NLO).
Insights from Chiral Polyfluorene on the Unification of Molecular Exciton and Cholesteric Liquid Crystal Theories for Chiroptical Phenomena
Publisher: American Chemical Society (ACS)
Date: 29-12-2011
DOI: 10.1021/JP209893H
Abstract: The Maugin-Oseen-DeVries theory accounts for chiroptical properties of cholesteric films with long-range order. For molecular systems with short-range structural correlation lengths, molecular exciton theory is used. A consistent description for systems with intermediate correlation lengths is lacking. Films of chiral polyfluorene behave according to Maugin-Oseen-DeVries theory when the film thickness exceeds 300 nm. Properties of thin films are consistent with molecular exciton theory. We describe the crossover in the optical properties of the film in a phenomenological way using a dielectric tensor that contains terms from Maugin-Oseen-DeVries and molecular exciton theory. Guided by the experimental findings, we explore the possibility of a unification of the Maugin-Oseen-DeVries and molecular exciton theory involving a coupled oscillator model.
Electronic energy transfer in highly aligned MEH-PPV single chains
Publisher: No publisher found
Date: 2011
DOI: 10.1021/JP204591P
Abstract: This paper describes the simultaneous measurement of excitation and emission anisotropy to visualize energy transfer in single chains of the prototypical conjugated polymer MEH-PPV, for s les with >70% of the single chains organized into extended, rod-like conformations. The uniformity and high degree of order of the single molecules in these experiments has allowed direct comparison of our experimental data to energy-transfer simulations in model polymer chains. Increases in average anisotropy from 0.62 to 0.74 from excitation to emission and average changes of <15° to the in-plane dipole principal orientation axis confirmed that energy was transferred to a relatively small number of sites in these highly ordered chains. This organization persisted even at large molecular weights (M(n) = 850 kDa). Electronic energy transfer in highly anisotropic model chains was simulated using an incoherent Förster-type mechanism to generate modulation depth histograms in good agreement with the observed data, as well as ensemble emission energies consistent with previously reported results. In these ordered model chains, excitons migrated an average of 6 nm before emission. This distance, far larger than the radius for single-step FRET, implies that energy transfer in MEH-PPV is a multistep funneling process.
Solution Epitaxy of Halide Perovskite Thin Single Crystals for Stable Transistors
Publisher: American Chemical Society (ACS)
Date: 27-07-2021
Voltage-dependent photocurrent transients of PTB7:PC70BM solar cells: Experiment and numerical simulation
Publisher: AIP Publishing
Date: 17-07-2013
DOI: 10.1063/1.4813612
Abstract: Transient photocurrent measurements on efficient polymer/fullerene solar cells based on a blend of the donor polymer PTB7 with the fullerene acceptor PC70BM are reported. In particular, we examine the light intensity dependence and voltage dependence of the turn-on and turn-off photocurrent dynamics of devices in response to a 200 μs square light pulse. At short circuit, subtle changes in the turn-on and turn-off dynamics are observed consistent with charge-density-dependent transport phenomena. As the working voltage is moved from short circuit to open circuit, we observe the appearance of an initial transient photocurrent peak a few microseconds after turn-on before the device settles to steady state. Furthermore, we observe only a weak dependence of the charge extraction dynamics on the working voltage, with the amount of charge extracted monotonically decreasing as the working voltage is moved from short circuit to open circuit. This collection of features is interpreted with the aid of numerical simulations in terms of charge trapping, with increased trap-assisted recombination closer to open circuit. The operation of devices fabricated with and without the solvent additive di-iodooctane is also compared. Charge trapping features are reduced for optimized devices fabricated with the solvent additive compared to devices fabricated without. The use of the solvent additive di-iodooctane in this system is therefore important in minimizing trap-assisted recombination.
Anisotropic Dielectric Tensor for Chiral Polyfluorene at Optical Frequencies
Publisher: American Chemical Society (ACS)
Date: 28-09-2009
DOI: 10.1021/JP907297Y
Abstract: The anisotropic dielectric tensor of chiral poly[9,9-bis((3S)-3,7-dimethyloctyl)-2,7-fluorene] is determined via variable angle spectroscopic ellipsometry and circular dichroism spectroscopy. The uniaxial anisotropy indicates a high in-plane alignment of polymer chains in the thin film. Chirality of the polymer results in small but nonzero off-diagonal matrix elements in the dielectric tensor, indicating a helical interchain organization in the vertical direction. This method for determining the dielectric tensor appears to be self-consistent when checked against various theoretical models for the optical activity in the reflection of light. The dielectric constants for the chiral polyfluorene are compared to those for an achiral polyfluorene.
FRET-enhanced photoluminescence of perylene diimides by combining molecular aggregation and insulation
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0TC02108C
Abstract: S les containing both molecularly insulated and aggregated perylene diimides at high concentration (140 mM) in polymer matrix showed very high photoluminescence quantum yield (85%) as a result of efficient energy transfer.
Polymer Photovoltaic Cells Sensitive to the Circular Polarization of Light
Publisher: Wiley
Date: 25-05-2010
Fluorescence Enhancement through Confined Oligomerization in Nanochannels: An Anthryl Oligomer in a Metal-Organic Framework
Publisher: American Chemical Society (ACS)
Date: 15-10-2021
Distributed feedback lasers up to the 400th Bragg order with an organic active layer
Publisher: AIP Publishing
Date: 09-01-2023
DOI: 10.1063/5.0131018
Abstract: The output characteristics and lasing threshold behavior of higher order Bragg lasers are explored using an organic active layer spin-cast over substrate-defined fused-silica gratings. Gratings ranging from 1st to the 400th Bragg order of varying duty cycle are fabricated with standard e-beam lithography. Distinct diffraction orders are observed at lower Bragg orders but smear out toward higher orders due to overlapping diffracted orders. Significant variation in thresholds is observed with duty cycle for most Bragg orders. A dramatic reduction in threshold is observed with increasing cavity length. The lowest lasing thresholds obtained for 4th and 400th order distributed feedback lasers are ∼1.4 and 4 μJ cm−2, respectively, using F80.9BT0.1 as an active layer. 400th order Bragg lasers are fabricated with direct-write photolithography using a UV laser diode, with comparable thresholds to e-beam lithography fabricated devices.
Strong coupling and energy funnelling in an electrically conductive organic blend
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0TC02239J
Abstract: A host–guest matrix enables both strong exciton-photon coupling and efficient energy transfer. This combination holds promise toward reduced laser thresholds and eventual electrical injection.
Circular Intensity Differential Scattering Reveals the Internal Structure of Polymer Fibrils
Publisher: American Chemical Society (ACS)
Date: 16-11-2019
DOI: 10.1021/ACS.JPCLETT.9B02993
Abstract: The optical and electronic properties of π-conjugated polymers in organic electronic devices depend on their intra- and interchain interactions, dictated by the internal arrangement of the polymer chains in an amorphous or semicrystalline aggregated state. Here, we discuss the utility of circular intensity differential scattering (CIDS) of circularly polarized light as a sensitive probe to identify the internal arrangement of the polymer chains in helical polymer aggregates. We advance existing theoretical models to utilize the CIDS response and extract structural properties such as the size, orientation, and periodicity of a polymer aggregate. As an ex le, we analyze the CIDS signatures of helically assembled fibrillar aggregates of a chiral polymer poly[(9,9-di-
Intensive Chiroptical Properties of Chiral Polyfluorenes Associated with Fibril Formation
Publisher: American Chemical Society (ACS)
Date: 07-10-2009
DOI: 10.1021/JP903083X
Abstract: Thin films of chiral poly{9,9-bis[(3S)-3,7-dimethyloctyl]-2,7-fluorene} (1) were studied using circular dichroism (CD) spectroscopy. Films spin coated from chloroform solution, show CD with a degree of polarization g(abs) (= +4 x 10(-4) at 400 nm) that is independent of film thickness (50-290 nm). This implies that g(abs) is an intensive property of the material and related to the chiral organization of the molecules on a length scale less than 50 nm. Atomic force microscopy (AFM) on the films reveals fibrils. Addition of nonsolvent methanol to a solution of 1 in chloroform leads to fibril formation in solution and results in CD similar in band shape to that of the pristine spin coated films from chloroform solution and a g(abs) comparable in magnitude. Thus the chiral molecular arrangement leading to circular dichroism is part of the internal structure of these fibrils.
Advancing Ocean Monitoring Near Coral Reefs
Publisher: American Geophysical Union (AGU)
Date: 12-10-2010
DOI: 10.1029/2010EO410001
Near-field circular polarization probed by chiral polyfluorene
Publisher: Optica Publishing Group
Date: 12-11-2009
DOI: 10.1364/OL.34.003571
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University Of Cambridge
Location: United Kingdom of Great Britain and Northern Ireland
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Linkage Infrastructure, Equipment And Facilities - Grant ID: LE150100075
Start Date: 2015
End Date: 03-2016
Amount: $240,000.00
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View Funded ActivityDiscovery Projects - Grant ID: DP160103008
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View Funded ActivityLinkage Infrastructure, Equipment And Facilities - Grant ID: LE210100151
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