Seoul National University-PolyU Bilateral Workshop - Flexible Organic and Perovskite Electronics
Chairman
Dean, Faculty of Science
Chair Professor of
Chemical Technology,
Department of Applied Biology and Chemical
Technology,
The Hong Kong Polytechnic University
Co-chair
Professor,
Department of Materials Science and Engineering,
Seoul National University
Co-chair
Chair Professor of Organic Electronics,
Department of Applied Physics,
The Hong Kong Polytechnic University
Member
Assistant Professor,
Department of Applied Biology and Chemical Technology,
The Hong Kong Polytechnic University
Member
Assistant Professor,
Department of Applied Physics,
The Hong Kong Polytechnic University
Member
Research Assistant Professor,
Department of Applied Biology and Chemical Technology,
The Hong Kong Polytechnic UniversitySpeakers from Korea
 Professor, |
Stretchable Hybrid Electronics (SHE) for Body-Attachable Display, Sensor, Thermoelectric ApplicationsAbstract With significant research in molecular electronics, new platform technology based on flexible and stretchable substrate, has gained a lot of attention in wearable fields. However, since there are still limitations in implementing high-performance wearable electronic system using novel materials and devices only, hybrid combination of both novel and conventional technologies, so called, hybrid stretchable electronics (SHE) technology has been considered a near-term solution. In this talk, my group's effort in SHE technology will be described. By isolating highly functional, typically rigid and brittle conventional components, from any external deformation stress, with stretchable spring-like interconnect conductors in between, we transforms conventional printed circuit boards (PCBs) and thermoelectric (TE) batteries into stretchable ones. Key enabling technology of SHE includes strain-engineering, stretchable interconnect, bonding of surface mount devices (SMDs), stretchable via and crossover. A new strategy based on soft modular block assembly is introduced to demonstrate fully customized wearable MP joint flexion monitoring system and robotic fingers. For a long-term solution toward low-cost and potentially disposable wearable devices, stretchable printed electronics technology can be used. SHE and printing technology would make paradigm shift of wearable electronic devices and help electronic skins and stretchable patch devices emerging in market as early as possible.
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 Professor, Department of Materials Science and Engineering |
Metal Halide Perovskite Nanocrystals for Next-Generation DisplaysAbstract Metal halide perovskites (MHPs) have emerged as promising candidates for future display technologies, primarily due to their superior high color purity. This talk will delve into the unique advantages and strategies of utilizing MHPs for display technologies, focusing on innovative nanostructures and material design approaches in precisely tailored colloidal perovskite nanocrystals (PNCs) to maximize luminous efficiency of perovskite light-emitting diodes (PeLEDs). First, we will introduce comprehensive material strategies aimed at suppressing defect generation, leading to the enhancement of the luminescent efficiency of PNCs. More specially, we incorporated zero-dipole guanidinium cation into formamidinium lead bromide (FAPbBr3) PNCs and utilized interlayer based on bromide-incorporated molecules. We also developed a modified bar-coating technique capable of producing large-area PeLEDs that match the efficiency of the PeLEDs with a small emission area. Additionally, we'll present an advanced core/shell PNC synthesis method, enabling to demonstration of simultaneously bright, efficient, and stable PeLEDs. Moreover, we will explore a novel hybrid tandem PeLEDs with an ideal optical structure that emits light more efficiently with a narrow bandwidth. Finally, we incorporated conjugated molecular multipods that reduce the dynamic disorder of perovskite, resulting in significantly improved luminescent efficiency of PeLEDs. These advancements highlight the potential of MHPs as promising materials for next-generation vivid displays.
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 Professor, |
Photo-response characteristics of molecular junctionsAbstract Photoresponsivity is a fundamental process that constitutes optoelectronic devices. In molecular junction devices, one of the most adopted strategies is to employ photoactive molecules that can undergo conformational change upon light illumination. In this talk, I first briefly summarize my group’s research work on the electrical transport properties of molecular-scale electronic junctions. Then, I will explain a series of research work on the photoswitching characteristics of diarylethene molecular junction devices that were made in three types of top electrodes (specifically, PEDOT:PSS, reduced graphene oxide, and graphene film top electrode) in the vertical junction structure. Also, I present a recent research work of photoswitching junctions made with molecules that have intrinsically little photoresponse and organohalide perovskite/graphene heterojunction as a photoactive electrode.
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 Professor, |
Harnessing Multiscale Chirality in Organic Semiconductors for Advanced OptoelectronicsAbstract Harnessing multiscale chirality in chiral organic semiconductors ranging from molecular to supramolecular chirality will open new opportunities for next-generation optoelectronics and spintronics. I will present synthesis of chiral organic semiconductors, fabrication of supramolecular semiconducting materials, structure-property relationships, and their applications in various physicochemical sensors. In addition, a simple yet powerful method to fabricate chiroptical flexible layers via supramolecular helical ordering of conjugated polymer chains will be introduced. These findings provide guidelines for enhancing chiroptical properties using multiscale chirality and rational molecular design of organic semiconductors toward high-performance chiral optoelectronics. In addition, these results demonstrate an effective strategy to realize on-chip detection of the spin degree of freedom of photons necessary for encoded quantum information processing and high-resolution polarization imaging.
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Professor, |
Glass transition temperature as a unified parameter to design self–healable elastomersAbstract Self–healing ability of materials, particularly polymers, improves their functional stabilities and lifespan. To date, the designs for self–healable polymers have relied on specific intermolecular interactions or chemistries. We report a design methodology for self–healable polymers based on glass transition. Statistical copolymer series of two monomers with different glass transition temperature (Tg) were synthesized, and their self–healing tendency depends on the Tg of the copolymers and the constituents. Self–healing occurs more efficiently when the difference in Tg between two monomer units is larger, within a narrow Tg range of the copolymers, regardless of their functional groups. The self–healable copolymers are elastomeric and nonpolar. The strategy to graft glass transition onto self–healing would expand the scope of polymer design. |
 Assistant Professor, |
Overcoming Doping Challenges in Emerging SemiconductorsAbstract Doping has been one of the most essential methods to control charge carrier concentration in semiconductors. Excess generation of charge carriers is a key route for controlling electrical properties of semiconducting materials and typically accompanies alteration of electronic structure by the introduction of dopant impurities, both of which have played pivotal roles in making breakthroughs in inorganic microelectronic and optoelectronic devices both at research and industrial levels, especially for Si-based technology. Molecular doping is a facile and effective doping method for various semiconducting materials since it is relatively non-invasive compared to high-energy implantation of ionic impurities used in Si. However, there are main challenges remaining in fully utilising molecular doping in emerging semiconducting materials such as π-conjugated polymer semiconductors, two-dimensional materials and metal-halide perovskites due to the difficulties in preventing dopant-induced disorder effects while maintaining a high carrier mobility. This talk will introduce concepts that we have developed to minimizing the dopant-induced disorder while mitigating current injection and doping stability issues in electronic devices, and finally outline the future challenges remaining in the field to fully uncover the potentials.
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Associate Professor, |
Quantum Dot Light-Emitting Diodes for Future DisplaysAbstract Colloidal quantum dots (QDs) have attracted great interest due to their unique optical and electrical properties, such as size-dependent bandgap tunability, broad absorption and narrow emission spectra, and controllable surface properties. Recently, several types of devices using QDs have been reported for future optoelectronics. The QD-based light-emitting diodes, QLEDs, are one of the most promising devices for future full-color displays and novel light sources. However, fundamental mechanisms such as charge injection into QDs, exciton recombination, and operational stability should be better understood and improved to commercialize the QLED displays. In this talk, I will mainly present our recent research progress on QLEDs, from fundamental understanding to practical applications. |
 Full Professor, |
A Monolithic Artificial Tactile Organic Synapse Using Piezo-ionics for Neuro-roboticsAbstract An iontronic-based artificial tactile nerve is a promising technology for emulating the tactile recognition and learning of human skin with low power consumption. However, its weak tactile memory and complex integration structure remain challenging. We present an ion trap and release dynamics (iTRD)-driven, neuro-inspired monolithic artificial tactile neuron (NeuroMAT) that can achieve tactile perception and memory consolidation in a single device. Through tactile-driven release of ions initially trapped within iTRD-iongel, NeuroMAT only generates non-intrusive synaptic memory signals when mechanical stress is applied under voltage stimulation. The induced tactile memory is augmented by auxiliary voltage pulses independent of tactile sensing signals. We integrate NeuroMAT with an anthropomorphic robotic hand system to imitate memory-based human motion; the robust tactile memory of NeuroMAT enables the hand to consistently perform reliable gripping motion.
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 Full Professor, |
From Graphene Oxide Liquid Crystal to Artificial MuscleAbstract Graphene Oxide Liquid Crystal (GOLC) is an intriguing 2D carbon based soft material, which exhibits nematic type colloidal discotic liquid crystallinity with the orientational ordering of graphene oxide flakes in good solvents, including water. Since our first discovery of GOLC in aqueous dispersion at 2009, this interesting mesophase has been utilized over world-wide for many different application fields, such as liquid crystalline graphene fiber spinning, highly ordered graphene membrane/film production for water treatment, nanoporous graphene assembly for energy/environmental applications and so on. Interestingly, GOLC also allow us a valuable opportunity for the highly ordered molecular scale assembly of functional nanoscale structures. This presentation will introduce our current status of GOLC and other 2D material research particularly focusing on the nanoscale assembly of functional nanostructures, including highly oriented 1D fibers, 2D films and 3D nanoporous structures. In particular, human muscle inspired graphene based nanocomposite fiber actuators will be highlighted along with its interesting demonstration for biomimetic behaviors. Besides, relevant research works associated to the nanoscale assembly and chemical modification of various low dimensional materials, including 2D TMDs and MXene, will be presented particularly aiming at energy and environmental applications. In the last part of presentation, our first discovery of single atom catalyst will be introduced, including other relevant research efforts exploiting the customized heteroelement doping of graphene based structures.
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 Professor, |
Self-assembled Halide Perovskites for Emerging PhotoelectronicsAbstract Halide perovskites (HPs) self-assembled into micro- or nanopatterns have attracted significant interest due to their potential to not only improve the efficiency of an individual device via the controlled arrangement of HP crystals, but also to develop multi-functional materials by facilitating unique photoelectric properties of a self-assembled host template. This presentation provides a comprehensive overview of the state-of-art bottom-up technologies used to develop micro- and nanometer scale HP patterns, and their potential for applications. Emphasis will be made on development of HPs self-assembled with block copolymers which exhibit excellent environmental stability, phase purity, and photoluminescence. Moreover, self-assembled dual-light-emitting materials are demonstrated for high-performance optical pattern encryption in which fluorescent HPs are stabilized and embedded in metal–organic frameworks (MOFs) designed for phosphorescent host–guest interactions. The presentation shows that self-assembled HPs reveal the unprecedented functionality of HPs, leading to new research areas that utilize their novel photophysical properties.
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Speakers from Hong Kong
 Sir Sze-yuen Chung Endowed Professor in Renewable Energy, |
Efficient and scalable perovskite photovoltaicsAbstract Solar photovoltaic (PV) energy has been playing an increasingly important role in the world’s energy portfolio. It is becoming a key contributor in the global transition to decarbonized electricity generation. Lead (Pb) halide perovskites have attracted great attention in PV due to their outstanding optoelectronic and defect properties. The research of halide perovskite solar cells continues to boom with device energy conversion efficiency approaching that of single crystal silicon solar cells The discovery of the extraordinary properties enables its application in efficient single-junction and multi-junction solar cells. In this talk, I will present the advance in understanding the optoelectronic properties of halide perovskites. One of the most promising, yet not heavily researched approaches is to make tandem solar cells using materials that function well even when they are polycrystalline and defective. Recent advances with hybrid perovskite semiconductors and their potential use in tandems will be emphasized. The progress of low-voltage deficit in wide bandgap perovskite and its application in high-performance perovskite-silicon tandem solar cells will be discussed. Besides, scaling up for perovskite-silicon tandem solar cells will also be briefed.
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 Chair Professor of Materials Physics and Chemistry, |
Synthesis of New Phase 2D All Organic Perovskites plus Spin-optoelectronics on 2D Hybrid Organic-inorganic perovskitesAbstract The perovskite materials, consisting traditionally of inorganic compounds, and more recently also the organic-inorganic hybrids, enjoy enduring interests from researchers owing to their impact on wide ranging fields, which include ferroelectrics, piezoelectrics and photovoltaics. Metal-free or all-organic perovskites are the newest addition to this family, but the synthetic methodology to make these are relatively undeveloped. Herein, we report the synthesis of metal-free 2D layered perovskite with the formula of A2B2X4, which we christened as Choi-Loh van der Waals phase (CL–v phase). CL-v phase is reminiscent of Ruddlesden–Popper phase in terms of having a van der Waals gap mediated by interlayer hydrogen bonding, and can be grown or exfoliated into 2D organic sheets. As a hallmark of layered materials with van der Waals gap, changes in interlayer sliding enables polymorphs to be synthesized.
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 Chair Professor of Frontier Materials, |
Heterostructure Engineering and Machine Learning in Advancing the Perovskite ElectronicsAbstract As an emerging class of light-responsive semiconductors, hybrid organo-metal perovskites seamlessly marry the characteristics of organic and inorganic materials, offering a new fertile playground to explore light-matter interaction. Perovskites have been the subject of scrutiny by materials scientists for over a hundred years, but the past decade has seen a surge in interest due to their remarkable photovoltaic properties, promising a breakthrough in solar energy. The hybrid characteristics and the strong correlation of composition/structure/function in these frontier materials bring new opportunities and challenges. Here, I will highlight our latest endeavors in engineering heterostructures with judiciously chosen semiconductor materials, particularly low-dimensional materials, which offer the promise of going beyond the limit of individual perovskite materials. Also, I will discuss using high-throughput calculation and machine learning to achieve precise control of the energy band structure to accelerate the discovery and design of new hybrid perovskite materials.
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Chair Professor of Organic Electronics, |
Flexible Organic Electrochemical Transistors for Sensing ApplicationsAbstract Organic electrochemical transistors (OECTs) have been successfully used in numerous sensing applications, such as biosensors, photodetectors and chemical sensors. Our group have been working on OECT–based sensors for many years. In this talk, I will introduce the following applications: (1) High-performance biosensors based on OECTs. By modifying the gate electrodes of OECTs, we have realized the detection of various type of biomolecules, such as IgG antibody, protein biomarkers and RNA. (2) OECTs based on highly oriented 2-dimensional conjugated metal-organic frameworks (2D c-MOFs) (Cu3(HHTP)2). The ion-conductive vertical nanopores formed within the 2D c-MOFs films lead to the most convenient ion transfer in the bulk and high volumetric capacitance, endowing the devices with fast speeds and ultrahigh transconductance. (3) Highly sensitive photodetectors based on perovskite solar cell-gated OECTs. The devices show ultrahigh sensitivity and fast response speeds. (4) Flexible phototransistors based on 2D c-MOFs (Cu3(HHTT)2) thin films. |
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Research Assistant Professor, |
Triplet Excited State-Utilizable Emitters for Optoelectronic ApplicationsAbstract Triplet excited state-utilizable emitters including phosphorescent transition-metal complexes (PTMCs) and thermally activated delayed fluorescence (TADF) materials have been attracting significant attention because of their excellent luminescent properties and promising optoelectronic applications. Different from conventional fluorescent materials, the triplet excited state-utilizable emitters can effectively utilize the triplet excited states by strong spin-orbit coupling effect, efficient reverse intersystem crossing process, etc. Manipulating the excited states of these emitters could endow them with appealing photophysical properties, which play vital roles in triplet state-related photofunctional applications. In this talk, I will introduce my recent progress on the molecular design, synthesis and optoelectronic applications of triplet excited state-utilizable emitters. The following topics will be covered: 1) Molecular engineering of iridium(III) complexes for highly efficient organic light-emitting devices (OLEDs); 2) Rational design of narrowband emissive thermally activated delayed fluorescence emitters for OLEDs; 3) Triplet-triplet annihilation/hybridized local and charge transfer-based emitters for OLEDs; 4) Molecular engineering of phosphorescent manganese(II) complexes for X‑ray scintillators. |
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Assistant Professor, |
Metallated Graphynes: Synthesis, Characterization and their ApplicationAbstract Transition metal ions as new functional units are introduced into the graphdiyne frameworks through metal-carbon linkages to form a novel kind of metallated graphyne via the matching effect of transition metal d orbitals and alkyne-based carbon p orbitals. This type of material will combine the dual advantages of both graphyne and transition metal ions to study its optoelectronic and catalytic properties. By constructing diverse molecular frameworks and transition metal types, the energy levels of molecular orbitals can be finely adjusted, as well as their photoelectric properties, catalytic performance. These 2D metallated graphynes not only exhibit excellent nonlinear optical properties, achieving short pulse laser output in laser devices. They also present high catalytic performance for O2 reduction to generate H2O2 and CO2 reduction reaction. The work can produce a new class of 2D carbon-rich materials and provide a design concept for developing efficient nonlinear optical materials and catalysts. |
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Assistant Professor, |
Computational Insights into Photophysics of Hybrid PerovskitesAbstract Computational materials science has evolved beyond elucidating material properties to include sophisticated theoretical frameworks that predict new materials and phenomena and describe photophysical processes across various simulation scales. This progress has led to diverse computational tools such as density functional theory (DFT), many-body perturbation theory (MBPT), and nonadiabatic molecular dynamics (NAMD). These methodologies often intersect, enriching interdisciplinary theoretical and computational materials research. With these advanced methodologies, we investigate hybrid perovskite materials, focusing on how dimensionality, crystal structure, and chemical composition influence their photophysical properties. We also highlight recent advancements in studying hot carrier cooling processes and manipulating organic spacers to enhance spin splitting in these materials. Our work demonstrates the potential of computational insights to drive the discovery and understanding of hybrid perovskites. |
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Research Assistant Professor, |
Organometallic Materials and Their Application in Solar Energy ConversionAbstract Solar energy technologies have gained significant global attention as crucial facilitators for the green and sustainable development of human society and the economy. Organic materials hold great potential in solar energy conversion due to their advantages, such as diverse molecular modification, pollution-free nature, low cost, solution processing, and flexible device fabrication. Our research focuses on developing novel organometallic materials and investigating their performance in solar cells and solar evaporators. The iridium and platinum-based molecules with high singlet-to-triplet conversion would be explored to improve the exciton lifetime and diffusion length, while also optimizing the active layer morphology to enhance the efficiency of organic solar cells. Additionally, a new strategy is proposed that integrates multiple charge transfer mechanisms, including metal-to-ligand, ligand-to-metal, ligand-to-ligand, and intermolecular charge transfers, into an organometallic polymer. This approach aims to design highly efficient photothermal materials for solar evaporation applications. The development of novel organometallic materials opens a meaningful pathway from molecular design to improving the solar energy conversion efficiency of both photo-to-electric and photo-to-thermal processes. |
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Research Assistant Professor, |
Artificial Photosynthesis via Covalent Organic Frameworks: a Tale of Charge and Mass TransportAbstract As the "holy grail" of modern chemistry, artificial photosynthesis is one of the most attractive and promising technologies and methods to solve the problems of energy shortage and environmental degradation. Covalent organic frameworks (COFs), which are covalently linked skeletons with high crystallinity and precise chemical structures, have exhibited great potential in the field of artificial photosynthesis. However, their structure-property-activity relationship, which should be beneficial for the structural design, is still far away explored. Here, we introduce different metal sites in COFs and ab initio construct a novel symmetry-breaking coordination environment, to regulate the photogenerated carrier migration and CO2 activation process from a molecular level, thereby effectively improving the performance of photocatalytic hydrogen production from water and aqueous CO2-to-CO conversion. |
 Associate Professor, |
In Situ Electropolymerizing toward Porous Nanofilms of Cobalt Porphyrin for Electrochemical CO2 ReductionAbstract Electrocatalytic CO2 reduction using cobalt porphyrin molecular catalysts shows promise in advancing the carbon cycle and combating climate change. Challenges persist in optimizing performance and evaluations due to low loading and utilization of electroactive sites. This study introduces a novel approach by synthesizing a monomer, CoP, and electropolymerizing it onto CNT networks to create a 3D microporous nanofilm (EP-CoP). EP-CoP enhances electron transfer, redox kinetics, and durability in CO2RR processes with a utilization rate of 13.1% and durability exceeding 40 hours. In a commercial flow cell, EP-CoP achieves a high FECO of 98.6% at 620 mV overpotential. Another study integrates EP-CoP onto a copper electrode to create an EP-CoP/Cu tandem catalyst for efficient C2 product formation. The electrode shows a high current density of 726 mA/cm2 at -0.9V vs. RHE with remarkable stability in flow cells, marking a significant advancement in electrochemical CO2 reduction catalysts.
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