A5100411995- Organic Electronics and Photovoltaics
- Conducting polymers and applications
- Organic Light-Emitting Diodes Research
- Perovskite Materials and Applications
- Molecular Junctions and Nanostructures
- Thin-Film Transistor Technologies
- Quantum Dots Synthesis And Properties
- Luminescence and Fluorescent Materials
- Advanced Sensor and Energy Harvesting Materials
- Advanced Photocatalysis Techniques
- Crystallization and Solubility Studies
- Food Quality and Safety Studies
- Fullerene Chemistry and Applications
- Chalcogenide Semiconductor Thin Films
- Nanowire Synthesis and Applications
- RNA Interference and Gene Delivery
- X-ray Diffraction in Crystallography
- ZnO doping and properties
- Advanced Memory and Neural Computing
- Photonic and Optical Devices
- Phytochemicals and Antioxidant Activities
- Plant-Derived Bioactive Compounds
- Photochemistry and Electron Transfer Studies
- solar cell performance optimization
- Education and Learning Interventions
Imperial College London
2016-2025
Sungkyunkwan University
2024-2025
University of Cambridge
1999-2024
Rural Development Administration
2016-2024
Yonsei University
2022-2024
University of Illinois Chicago
2024
Dong-A University
2024
Catholic University of Korea
2023
Konkuk University
2016-2023
Centre for Process Innovation
2021
The absorption spectrum of polythiophene and its derivative poly(3-hexylthiophene) (P3HT) is usually described in terms an intrachain exciton coupled to a single phonon mode. We show that this model too simplistic for highly ordered, regioregular P3HT that, analogous the case charged polarons material, interchain interactions must be taken into account correctly describe spectrum. lowest energy feature $\ensuremath{\pi}\ensuremath{-}{\ensuremath{\pi}}^{*}$ region associated with absorption,...
We report combined studies of the influence chemical and physical treatments on properties indium–tin oxide (ITO) thin films. The ITO films were also used as transparent anodes polymeric light-emitting diodes (LEDs) incorporating poly(p-phenylene vinylene) (PPV) emitter material, with, or without, doped poly(3,4-ethylene dioxythiophene) (PEDOT) a hole-injection/transport layer. Structures based soluble green derivative PPV, poly(4,4′-diphenylene diphenylvinylene) tested. studied (aquaregia,...
We report electroabsorption measurements of polymer light-emitting diodes, (LEDs), fabricated with poly(4-4′-diphenylene diphenylvinylene), PDPV, as the emissive layer, Ca–Al cathodes, and indium tin oxide (ITO) anodes, without a doped conducting hole injection/transport namely poly(3,4-ethylene dioxythiophene), PEDOT, poly(styrene sulfonate), PSS−. In these structures, bias at which signal is null corresponds to difference between electrodes’ work functions. find that such built-in voltage...
The electroluminescence (EL) pattern emitted through the surface and edge of glass substrate two efficient polymer light-emitting diodes (LEDs) has been characterized. emission is nearly Lambertian, while comprises discrete reflection leaky waveguide modes. A simple “half-space” optical model that accounts for interference effects metal cathode–reflector developed to extract location orientation emitting dipoles from these patterns. Numerical simulations a range refractive indices show...
The nature of main in-plane skeleton Raman modes (C=C and C-C stretch) poly(3-hexylthiophene) (P3HT) in pristine its blend thin films with [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) is studied by resonant nonresonant spectroscopy simulations. Under conditions, the ordered phase P3HT respect to disordered identified (a) a large shift C=C mode peak position lower wavenumber (~21 cm(-1) shift), (b) narrower fwhm (~9 narrower), (c) larger intensity relative (~56% larger), (d) very small...
Bright, ambipolar, light-emitting polymer field-effect transistors in a bottom-contact/top-gate structure using poly(9,9-di-n-octylfluorene-alt- benzothiadiazole) (F8BT) as green-emitting semiconductor show balanced hole and electron mobilities, depending on the dielectric. The emission zone, observed bright line figure, is well defined can be moved through channel.
Spin-coated poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) films of different molecular weights (Mn= 9-255 kg/mol), both in the pristine and annealed state, were studied an effort to elucidate changes polymer packing structure effects this has on optoelectronic charge transport properties these films. A model based quantum chemical calculations, wide-angle X-ray scattering, atomic force microscopy, Raman spectroscopy, photoluminescence, electron mobility measurements was developed...
Charge carrier mobility is a figure of merit commonly used to rate organic semiconducting materials for their suitability in applications such as solid-state lighting or photovoltaics. Although large variations are found published values on identical materials, there little open discussion the literature reproducibility these results. We address this with an interlaboratory study measurements performed set semiconductors using space-charge limited current method. measured nominally devices...
We study thin films of semi-crystalline regioregular poly(3-hexylthiophene) (RR-P3HT) and amorphous regiorandom P3HT (RRa-P3HT) in blends with [6,6]-phenyl C61 butyric acid methyl ester (PCBM). Ultraviolet (angle-resolved) X-ray photoelectron spectroscopy techniques together absorption, photoluminescence optical microscopy were used to measure electronic energy levels, vertical chemical compositions properties these films. find that ordering the chains raises highest occupied molecular...
We report two strategies toward the synthesis of 3-alkyl-4-fluorothiophenes containing straight (hexyl and octyl) branched (2-ethylhexyl) alkyl groups. demonstrate that treatment dibrominated monomer with 1 equiv Grignard reagent leads to formation a single regioisomer as result pronounced directing effect fluorine group. Polymerization resulting species affords highly regioregular poly(3-alkyl-4-fluoro)thiophenes. Comparison their properties those analogous non-fluorinated polymers shows...
Abstract Organic solar cells (OSCs) based on nonfullerene acceptors (NFAs) have made significant breakthrough in their device performance, now achieving a power conversion efficiency of ≈18% for single junction devices, driven by the rapid development molecular design and engineering recent years. However, long‐term stability remains major challenge to overcome commercialization, due large part current lack understanding degradation mechanisms as well rules enhancing stability. In this...
In this study, we investigate the underlying origin of high performance PM6:Y6 organic solar cells.
A comparison of the efficiency, stability, and photophysics organic solar cells employing poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3'″-di(2-octyldodecyl)-2,2';5',2″;5″,2'″-quaterthiophen-5,5'″-diyl)] (PffBT4T-2OD) as a donor polymer blended with either nonfullerene acceptor EH-IDTBR or fullerene derivative, [6,6]-phenyl C71 butyric acid methyl ester (PC71 BM) electron acceptors is reported. Inverted PffBT4T-2OD:EH-IDTBR blend cell fabricated without any processing additive...
This review highlights the opportunities and challenges in stability of organic solar cells arising from emergence non-fullerene acceptors.
An effective strategy to engineer selective photodynamic agents surmount bacterial-infected diseases, especially Gram-positive bacteria remains a great challenge. Herein, we developed two examples of compounds for proof-of-concept study where reactive differences in oxygen species (ROS) can induce ablation bacteria. Sulfur-replaced phenoxazinium (NBS-N) mainly generates superoxide anion radical capable selectively killing bacteria, while selenium-substituted (NBSe-N) has higher generation...
PSS is widely used as a hole transport layer (HTL) in perovskite solar cells (PSCs) due to its facile processability, industrial scalability, and commercialization potential. However, PSCs utilizing PEDOT:PSS suffer from strong recombination losses compared other organic HTLs. This results lower open-circuit voltage (VOC) power conversion efficiency (PCE). Most studies focus on doping improve charge extraction, but it has been suggested that high level can cause losses. Herein, we...
The non-fullerene acceptors (NFAs) employed in state-of-art organic photovoltaics (OPVs) often exhibit strong quadrupole moments which can strongly impact on material energetics. Herein, we show that changing the orientation of Y6, a prototypical NFA, from face-on to more edge-on by using different processing solvents causes significant energetic shift up 210 meV. this OPV performance is investigated both bilayer and bulk-heterojunction (BHJ) devices with PM6 polymer donor. device electronic...
The poor operational stability of non-fullerene electron acceptor (NFA) organic solar cells (OSCs) currently limits their commercial application. While previous studies have primarily focused on the degradation NFA component, we also consider here donor material. We examine three representative polymers, PM6, D18, and PTQ10, paired with benchmark NFA, Y6. After light soaking PM6 D18 in air, find an enhanced conversion singlet excitons into trapped interchain polaron pairs sub-100 femtosecond...
Metal batteries have captured significant attention for high-energy applications, owing to their superior theoretical energy densities. However, practical viability is impeded by severe dendrite formation and poor cycling stability. To alleviate these issues, a 3D-structured bimetallic-Mo2Ti2C3Tx based fiber electrode was fabricated in this study analyzed experimentally computationally. The bimetallic Mo–Ti composition of MXenes synergistically achieved low binding energies with lithium. In...
A novel barrier‐free mechanism for electron–hole capture at heterojunctions between two semiconductor polymers is shown to occur in highly efficient light‐emitting diodes (LEDs). Electron–hole across the heterojunction forms an exciplex—a localized state—and subsequent endothermic energy transfer produces emissive excitons. This process only requires low charge densities interface, enabling excellent LED performance.
We report that adding a thin (∼10nm) semiconducting polymer interlayer between apoly(styrenesulphonate)-doped poly(3,4-ethylenedioxythiophene) (PEDT:PSS) hole transporter and an emissive semiconductor significantly improves the device efficiency of light-emitting diodes (LEDs). With interlayer, external quantum (EQE) increases from 0.7%(0.4cd∕A at 3.7V) to 1.9% (1.0cd∕A 3.3V) 100cd∕m2 for red LEDs 1.9%(6.2cd∕A 3.4V) 3.0% (10.1cd∕A 3.0V) 1000cd∕m2 green LEDs. An EQE 4.0% is also observed in...
Tetrafluoro-tetracyano-quinodimethane (F4TCNQ) is used to p-dope conjugated polymers with a wide range of the HOMO levels via co-blending in common organic solvent. Doping results several orders magnitude increase bulk conductivity and hole-current reduced turn-on voltage. The effectiveness doping increases as level polymer becomes smaller.