Yoon Ho Lee

Graphene‐based chemical sensors offer high sensitivity owing to exceptional charge transport and a large surface‐to‐volume ratio, yet reliable discrimination across diverse analytes remains challenging. In this study, a letterpress‐inspired, one‐step transfer‐printing strategy integrated with pattern‐recognition analysis is proposed to implement multiplexed chemical sensor arrays based on graphene field‐effect transistors (GFETs). By tuning interfacial adhesion between functional materials and a polymer stamp, accurate and area‐selective functionalization with sub‐10 µm feature sizes is achieved, thereby enabling simultaneous multifunctionalization of graphene. The resulting 3 × 3 GFET sensor arrays, comprising both functionalized and pristine channels, generate distinct sensing response patterns to representative volatile organic compounds, including chlorobenzene, toluene, and methanol, at a fixed tested concentration, driven by molecule‐specific charge‐transfer interactions at the functional layer. An artificial neural network trained on sensor‐derived patterns is further demonstrated with an increased number of sensors, delivering highly accurate classification results. This strategy highlights a versatile and scalable platform that combines lithography‐free, low‐cost transfer printing with intelligent analysis, offering a practical route toward next‐generation chemical‐sensing systems based on functionalized 2D materials.

Chiral halide perovskites are promising materials for circularly polarized light (CPL) optoelectronics owing to their strong light absorption, long carrier diffusion lengths, and intrinsic chiroptical activity. However, most reported CPL perovskite devices still suffer from limited chiroptical selectivity and poor operational stability, hindering practical applications. Here, we report a facile interfacial passivation strategy using an atomic layer deposition (ALD)‐grown AlF ₃ film for high‐performance and stable CPL photodetectors (PDs). The dense AlF ₃ underlayer modifies the local interfacial environment of the perovskite, promotes grain growth, and reduces defect sites in the chiral perovskite films. Consequently, the AlF ₃ ‐based films exhibit enhanced apparent chiroptical properties, with circular dichroism (CD) and circularly polarized photoluminescence (CPL‐PL) g ‐factors increasing by approximately 3.8‐fold and 2‐fold, respectively, compared with pristine films. CPL PDs fabricated on the AlF ₃ underlayer achieve a photoresponsivity of 54 mA W ⁻¹ , a specific detectivity of 1.68 × 10 ¹¹ Jones, and a photocurrent g ‐factor of 0.48, representing an 84% enhancement over pristine devices. Interfacial AlF ₃ passivation also significantly improves device durability, providing a T ₇₀ operational lifetime more than 9.3 times longer under ambient conditions. This work demonstrates an effective interface‐engineering strategy for simultaneously enhancing chiroptical selectivity, device performance, and operational stability in CPL perovskite optoelectronics.

Scalable fabrication of uniform perovskite films is a critical bottleneck for large-area perovskite light-emitting diodes (PeLEDs), hindered by coffee-ring formation and heterogeneous crystallization upon scaling. Here, we report a multimodal solvent-engineering strategy enabling highly uniform films via ambient blade coating combined with vacuum-assisted solvent evaporation. Incorporating N -methyl-2-pyrrolidone (NMP) and acetonitrile (ACN) into a dimethylformamide (DMF)–based system synergistically modulates evaporation dynamics: It suppresses macroscopic solute segregation through Marangoni flow–induced redistribution, while tuning precursor coordination to regulate nucleation/phase conversion and promote radiatively efficient film formation. Consequently, the ternary formulation yields films with improved uniformity, reduced trap densities, and enhanced radiative efficiency. Near-infrared (NIR) PeLEDs achieve peak external quantum efficiencies of 25.2% (10 mm ² ), 22.1% (60 mm ² ), and 19.0% (224 mm ² ). A functional vein-imaging prototype is also demonstrated using a 224-mm ² device, highlighting the impact for large-area optoelectronic applications.

Eco‐friendly, disintegrable encapsulation materials are gaining attention as alternatives to conventional plastics in electronic devices. However, achieving simultaneous oxygen and moisture barrier performance with high optical transparency remains challenging. In this work, a large‐area hybrid encapsulation composite films are developed by infiltrating polylactic acid (PLA) into TEMPO‐oxidized cellulose nanofibers (ToCN) via a capillary rise infiltration (CaRI) process, achieving a uniform film over an area of 230 × 175 mm ² . The ToCN‐PLA hybrid film exhibits over 90% transmittance in the visible range, along with significantly reduced oxygen permeability and water vapor transmission rate of 3 mL·m ⁻² ·day ⁻¹ Pa ⁻¹ and 30 mL·m ⁻² ·day ⁻¹ , respectively, compared to the individual PLA and ToCN films, while also offering biodegradability. Moreover, the hybrid film demonstrates excellent mechanical properties, with tensile strength and Young's modulus improved by ≈30% and 26%. Furthermore, device integration tests using 2D halide perovskite‐based photodetectors demonstrate that encapsulation with the hybrid film significantly enhances operational stability in humid and oxygen‐rich environments, achieving a 1.3 fold increase in T ₇₀ lifetime relative to conventional poly(methyl methacrylate) (PMMA) encapsulation layers. These results demonstrate that CaRI produced ToCN‐PLA composite film can effectively overcome individual material limitations, providing a scalable and sustainable strategy for next‐generation optoelectronic encapsulation.

Perovskite materials have emerged as promising candidates for next-generation photodetectors (PDs) owing to their superior optoelectronic properties and compatibility with low-cost, low-temperature fabrication processes. Broad applicability of PDs spans diverse fields, including X-ray detection, wearable electronics, autonomous vehicles, artificial intelligence, imaging, optical communication, and biomedical sensing, offering advantages over conventional semiconductor PDs based on Si, Ge, InGaAs, and GaN. The integration of plasmonic nanostructures into perovskite-based devices has recently emerged as an effective strategy to enhance performance by amplifying light absorption near the perovskite layer. This review summarizes recent advances and design strategies for plasmonic-integrated perovskite photodetectors (Pe-PDs), with a particular emphasis on plasmonic nanopatterns and nanoparticles as viable approaches for solution-processable Pe-PDs.

Mechanoresponsive polymeric materials that respond to mechanical deformation are highly valued for their potential in sensors, degradation studies, and optoelectronics. However, direct visualization and detection of these responses remain significant obstacles. In this study, novel mechanoresponsive polybiidenedionediyl (PBIT) derivative topochemical polymers are developed that depolymerize under mechanical forces, exhibiting a distinct and irreversible color change in response to grinding, milling, and compression. This color change is attributed to the alteration of polymer backbone conjugation during elongated Carbon‐Carbon (C─C) single bond cleavage. Quantum chemical pulling simulations on PBIT polymers reveals a force range of 4.3–5.0 nN associated with the selective cleavage of elongated C─C single bonds. This force range is comparable to that observed for typical homolytic mechanophores, supporting the mechanistic interpretation of homolytic bond scission under mechanical stress. C─C bond cleavage kinetic studies of PBIT under compression indicates that strong interchain interactions significantly increase the pressure needed to cleave the elongated C─C bonds. Additionally, PBIT polymer thin films are composited with polydimethylsiloxane to create free‐standing and robust thin films, which can serve as ink‐free and rewritable paper for writing and stress visualization applications. This advancement opens new possibilities for utilizing crystalline and brittle topochemical polymers in practical applications.

The field of neuromorphic computing has seen significant advancements through the development of artificial synapses, with two-dimensional (2D) and quasi-2D halide perovskites emerging as key materials in this area. These materials exhibit remarkable properties such as resistive switching, fast charge carrier mobility, and low power consumption, making them ideal candidates for emulating synaptic behavior in artificial neural networks. This article reviews the fundamental principles behind artificial synapses and explores the progress made in utilizing 2D and quasi-2D halide perovskites for synaptic emulation. Key phenomena like short-term and long-term potentiation, spike-timing dependent plasticity, and associative learning are replicated in these materials, offering insights into their potential applications in energy-efficient computing systems. Furthermore, the challenges associated with air stability and the ongoing efforts to improve the performance and reliability of perovskite-based synaptic devices are thoroughly examined. The review also highlights the promising future of these materials in applications ranging from visual systems to sensory adaptation and beyond. This article provides a comprehensive overview of the current state of research in perovskite-based artificial synapses and their role in advancing neuromorphic computing.

Surface passivation is evident to be one of the most efficient approaches to achieve high efficiency with superior stability of perovskite solar cells (PeSCs). However, most previous approaches to surface passivation involve adding an additional coating process either before or after perovskite film fabrication, thereby introducing an extra processing step and significantly increasing production costs. Here, a simple yet novel one-step interfacial passivation approach was implemented by utilizing the self-aligning properties of fluorinated organic ligands (F4TmI) within a perovskite precursor solution. The inherent propensity of the ligand to spontaneously anchor onto the surface of perovskite guides the crystallization process of perovskites, thus largely enhancing the device performance and humidity stability. The optimized F4TmI-based devices achieved an efficiency of 21.1%, surpassing that of the control (19.8%). Moreover, the device stability significantly improved after the incorporation of F4TmI, maintaining 78.9 and 95.1% of its initial efficiency after aging at 60 °C and 60% relative humidity, respectively, for 330 h.

2D perovskite (PVSK) single crystals have received significant attention due to their unique optical and optoelectronic properties. However, current synthesis methods face limitations, particularly in large‐area fabrication, which remain critical barriers to practical applications. In this study, the synthesis of red/green/purple‐blue‐colored 2D PVSK nanocrystals over a large area (4‐inch wafer) and the fabrication of high‐performance photodetector arrays are presented via a facile yet efficient spray‐coating approach with a liquid‐bridge transport effect. The photodetector array achieves 100% working yield, high photo‐responsivity (1.5 × 10⁶ A W⁻¹) and specific‐detectivity (1.1 × 10¹⁶ Jones) with competitive photomapping characteristics. An intelligent vision system for automatic shape recognition is further demonstrated with a recognition rate exceeding 90%. This study provides significant advances in the scalable synthesis of nanoscale 2D PVSK crystals, their integration into large‐area optoelectronic devices, and their potential use in artificial‐intelligence systems.

Two-dimensional (2D) perovskites have gained much attention lately owing to their excellent optoelectronic properties, chemical tunability, and environmental stability. Multiple methods have been devised to synthesize high quality 2D perovskite single crystals, and recent progress in fabricating its heterostructures is notable as well. In particular, with growing interest in 2D van der Waals heterostructures, 2D perovskites have become a strong candidate as a new building block for heterostructures to reveal unique physical properties across different interfaces. Until now, various heterostructure devices of 2D perovskite single crystals with other types of 2D materials such as transition metal dichalcogenides (TMDs) and graphene have been studied, which have shown intriguing results including interlayer excitons and enhanced electronic properties. Here, we introduce various synthetic approaches to realize 2D perovskite single crystals and unique characteristics of their single crystal heterostructures fabricated with precision, possessing sharp interfaces. Moreover, recent studies of semiconductor devices based on 2D perovskite single crystal heterostructures are discussed in-depth. New perspectives to further the horizon in the field of 2D perovskite heterostructures are suggested in this work including the consideration of metal–2D material van der Waals contact, application of dry transfer techniques, electric bias driven ion diffusion studies, and nanocrystal array fabrication. 2D perovskite heterostructure single crystal devices factoring in these novel perspectives will further uncover the true potential of these materials for highly efficient and stable semiconductor devices.