Seoul National University-PolyU Bilateral Workshop - Flexible Organic and Perovskite Electronics 2024
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,
Speakers from Korea
 Professor, Department of Materials Science and Engineering |
Stable, Scalable, and Efficient Perovskite Nanocrystal Emitters for Vivid DisplaysAbstract Metal halide perovskites (MHPs) have emerged as promising light emitters for next-generation displays and optoelectronics, owing to their excellent color purity, tunable emission, and high photoluminescence quantum yield (PLQY). However, translating these intrinsic optical merits into practical display devices requires further improvements in efficiency and operational stability. This presentation presents molecular and structural strategies that address both challenges in perovskite light-emitting diodes (PeLEDs). Doping guanidinium (GA) cations into FAPbBr3 nanocrystals (PNCs) with bromide-incorporated overcoating passivates surface defects; surface-binding conjugated molecular multipods strengthen the lattice and reduce dynamic disorder; and benzylphosphonic-acid core/shell structures further boost efficiency and stability. Toward commercialization, a scalable cold-injection synthesis achieves near-unity PLQY at large scale with a high external quantum efficiency (EQE) of 29.6%. Ultra-stable multi-layer-shell PNCs withstand 60°C and 90% relative humidity and high light flux, enabling down-converting LEDs covering over 95% of the Rec. 2020 color space, demonstrating strong commercial potential.
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 Professor, |
Molecular-scale Synaptic Transistors with Redox-Induced Analog StatesAbstract In this talk, I will report a three-terminal, ion-gel-gated, redoxactive molecular transistor that exhibits synaptic plasticity and analog conductance states. The device was composed of a ferrocene-terminated alkanethiolate self-assembled monolayer as the active channel, vertically sandwiched between a monolayer graphene source and a Au drain, and the channel conductance was modulated by an ion-gel gate. Gate voltage pulses induce an electric double layer at the ion-gel/graphene interface, triggering dynamic postsynaptic-like current responses. Our device exhibited neuroinspired plasticity, including short-term plasticity like paired-pulse facilitation and a programmable transition to long-term plasticity upon repeated stimulation. The ferrocene redox moiety was identified as the key enabler of nonvolatile switching behavior, mediating a dynamic, voltage-programmable conductance change via a synergistic mechanism of reversible redox and ion trapping. These results establish vertical molecular transistor systems as a building block for molecular-level neuromorphic hardware, with a three-terminal, read/write-decoupled architecture.
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 Associate Professor, |
Ionic-Electronic Coupling in Emerging SemiconductorsAbstract Ionic-electronic coupling is a fundamental governing interaction that dictates the generation and transport of ionic and electronic charges in mixed ionic-electronic conductors. Utilising such effect in emerging semiconductors, such as organic mixed ionic-electronic conductors (OMIECs) has demonstrated am impressive ionic-electronic transconduction, in a device form of electrochemical transistors. Here, we present OMIEC material designs for attaining high figure-of-merit (µC*) and excellent operational stability by developing a robust mixed-conductors in aqueous environment. In addition to the balanced mixed conduction, efficient ionic-electronic coupling, the system exhibits a remarkable doping stability, a key factor for reliable OECT function. This work aims to offer insights into rational and versatile design strategies to fundamentally decouple ionic mobility from structural instability, providing routes for developing organic electrochemical devices practically relevant for bio-and neuromorphic electronics.
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 Professor, |
Electron-Beam–Assisted Mechanical Deformation in Oxide CeramicsAbstract Electron-beam–induced electronic excitation offers a non-thermal pathway to modify deformation mechanisms and drive nanostructure evolution in oxide ceramics. In this study, we demonstrate that electron–matter interactions significantly alter size-dependent mechanical behavior in both amorphous and crystalline systems, enabling precise nanoscale structural control. In amorphous silica, in-situ mechanical compression with focused low-voltage electron irradiation induces athermal viscoplastic deformation and densification at room temperature, permitting localized shaping without external heating. Furthermore, irradiation promotes the solid-state mechanical amorphization of crystalline α-quartz under ambient conditions. These phenomena are attributed to beam-induced delocalized electrons that screen interatomic repulsive forces, thereby lowering the energy barriers for atomic rearrangement. We believe that these findings establish electronic-structure manipulation as a robust strategy for defect engineering and deformation control in ceramics. This work provides a framework for designing nanostructured materials with tailored mechanical performance for extreme environments.
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Assistant Professor, |
Atomic Reconstruction at Engineered van der Waals InterfacesAbstract Twisted interfaces between two-dimensional (2D) van der Waals (vdW) materials enable control of structural symmetry and functionality at the atomic scale. Varying the stacking angle produces moiré superlattices and lattice reconstruction, where interlayer registry competes with intralayer strain to form ordered domains with emergent electronic, optical, or ferroic properties. This talk will show how stacking configurations and reconstruction govern domain formation and functionality, examined by electron diffraction contrast in transmission electron microscopy (TEM). By integrating TEM with semiconductor device fabrication, we perform operando measurements of domain dynamics in working devices, directly linking local symmetry breaking to macroscopic responses such as ferroelectric switching in twisted bilayer TMDs. Extending to multilayers introduces additional interfaces and symmetry degrees of freedom, yielding complex tessellations with distinctive structural and functional characteristics. Understanding these reconstructions is key to controlling emergent phenomena in twisted vdW materials. |
 Associate Professor, |
Designing Light at the Source: k-Space Mode Engineering for Directional and Chiral Thin-Film EmittersAbstract Controlling the direction and polarization of light at the emission stage is a key challenge for thin-film optoelectronics, where spontaneous emission is intrinsically broad and post-emission optics add loss and system complexity. In this talk, I will discuss k-space mode engineering in photonic-crystal platforms as a route to design how light is generated, extracted, and polarized. I will first show how all-dielectric photonic crystals coupled to thin-film emitters convert trapped guided modes into radiative channels, enabling brighter and highly directional emission. I will then describe symmetry-broken quasi-bound states in the continuum that provide deterministic control of chiral emission at the normal direction. Finally, I will discuss electrically driven photonic-crystal surface-emitting devices, highlighting how band-edge feedback can be implemented in practical laser-diode structures. These examples illustrate how subwavelength optical structures can turn thin-film emitters into efficient, directional, and polarization-controlled light sources for future photonic and display applications.
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Professor, |
Tailoring the Electrical–thermal Properties of Polymers for Thin-film ThermoelectricsAbstract Thin-film thermoelectrics based on solution-processable soft materials, including conducting polymers, carbon nanotubes, and colloidal quantum dots, are promising for flexible and wearable energy harvesting, but remain limited by coupled electrical and thermal transport. In this presentation, a variety of strategies are presented for tailoring electrical and thermal properties through independent control of charge and heat pathways. Electrical transport is enhanced by tuning microstructure, electronic coupling, and carrier density, enabling semi-metallic or highly conductive behavior while maintaining favorable thermopower. Thermal transport is suppressed or redirected through phonon-scattering interfaces, low-conductivity phases, and thermally anisotropic architectures that convert out-of-plane heat flow into in-plane voltage generation. By decoupling electron and phonon transport across material and device length scales, these approaches provide general design principles for high-performance, scalable, and mechanically compliant energy-harvesting platforms. |
 Distinguished Professor, |
Sustainable Silicone Lithography of Organic Semiconductors for Human-interactive, High-resolution RGB OLED MicrodisplayAbstract Ultrahigh-resolution patterning with high throughput and fidelity is critical for extending organic light-emitting diodes (OLEDs) from conventional displays to near-eye microdisplays. However, existing patterning approaches remain limited by insufficient resolution, poor pattern fidelity, and constraints in scalable RGB integration. Here, we introduce a silicone-engineered anisotropic lithography for organic light-emitting semiconductors (OLES), in which a non-volatile etch-blocking layer is formed in situ during reactive ion etching. This self-limiting mechanism simultaneously suppresses lateral etching and enhances directional anisotropy, enabling precise and reproducible pattern definition. As a result, ultrahigh-density OLES patterns exceeding 10,000 pixels per inch are achieved through anisotropic photolithography, providing unprecedented control over sub-micron pixel architectures. By translating principles from silicon etching chemistry into organic semiconductor processing, this strategy establishes a new pathway toward scalable, high-resolution RGB patterning in OLED-on-silicon (OLEDoS) platforms for next-generation extended reality (XR) displays.
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 Professor, |
Sensory Neuromorphic Displays for Biomedical and Robotic ApplicationsAbstract Human-interactive technologies play a crucial role in intelligent IoT, bioelectronics, and emerging physical AI regimes. Sensory neuromorphic displays (SNDs) integrate sensory processing, computation, memory, and visualization into a unified system, addressing the key limitations of traditional displays such as limited adaptability, high power consumption, and lack of contextual awareness. By leveraging neuromorphic computing principles and advanced device architectures, these displays enable real-time, adaptive responses to environmental stimuli, enhancing energy efficiency and interactivity. The development of innovative one-integrated platforms with optimized architectures where all the functional components are converged is essential to achieve highly efficient and fast information management. The presentation introduces a light-emitting tactile sensory neuromorphic display for real-time monitoring of finger rehabilitation movements. The core structure is based on a polymer electrochemical transistor (OECT) with an elastomeric tactile receptor and an electrochemiluminescent ion gel as the light-emitting layer. The approach presents a highly interactive, low-power solution for personalized rehabilitation monitoring. The SND platform also detects, memorizes, and visualizes magnetic field with an elastomeric gate modified with ferromagnetic fillers, demonstrating its feasibility and versatility for compact, energy-efficient wearable and physical AI robotic applications.
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 Professor, |
Multi-dimensional Bioelectronic Interfaces and Energy Devices Based on Crystalline PEDOT:PSSAbstract In this research, we report organic bioelectronic interfaces based on highly crystalline poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) films and microfibers, designed to overcome the inherent trade-off between electrical/electrochemical performance and long-term stability in aqueous environments. The crystalline PEDOT:PSS films exhibit excellent electrical, electrochemical, and optical properties, alongside robust long-term stability in water, and demonstrate high biocompatibility for primary-cultured cardiomyocytes and neurons over several weeks. Leveraging these properties, we successfully employ these films in high-performance multi-electrode arrays (MEAs) to record and stimulate the electrophysiological activities of primary cardiomyocytes and chicken retina tissues. In parallel, we develop crystalline PEDOT:PSS microfibers and a specialized self-fusion process to create single-strand wearable electrochemical transistors and 3D microfibrillar network-based bioelectronic interfaces. Finally, we discuss ongoing research activities, including the direct crystallization of PEDOT:PSS on plastic substrates, core-shell fibers and 3D sponges for energy storage, and PEDOT:PSS composite materials for electrocatalysis, gas separation membranes, and degradable/sustainable electronics.
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Invited Speakers
 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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