Kyungyeon Ha

Bio: Kyungyeon Ha is an academic researcher from Seoul National University. The author has contributed to research in topics: Surface plasmon & Nanoparticle. The author has an hindex of 8, co-authored 11 publications receiving 296 citations.

Plasmonic Organic Solar Cells Employing Nanobump Assembly via Aerosol-Derived Nanoparticles

Abstract: We report the effect of a nanobump assembly (NBA) constructed with molybdenum oxide (MoO3) covering Ag nanoparticles (NPs) under the active layer on the efficiency of plasmonic polymer solar cells. Here, the NPs with precisely controlled concentration and size have been generated by an atmospheric evaporation/condensation method and a differential mobility classification and then deposited on an indium tin oxide electrode via room temperature aerosol method. NBA structure is made by enclosing NPs with MoO3 layer via vacuum thermal evaporation to isolate the undulated active layer formed onto the underlying protruded NBA. Simulated scattering cross sections of the NBA structure reveal higher intensities with a strong forward scattering effect than those from the flat buffer cases. Experimental results of the device containing the NBA show 24% enhancement in short-circuit current density and 18% in power conversion efficiency compared to the device with the flat MoO3 without the NPs. The observed improvemen...

Hotspot‐Engineered 3D Multipetal Flower Assemblies for Surface‐Enhanced Raman Spectroscopy

Abstract: Novel 3D metallic structures composed of multipetal flowers consisting of nanoparticles are presented. The control of surface plasmon hotspots is demonstrated in terms of location and intensity as a function of petal number for uniform and reproducible surfaceenhanced Raman spectroscopy (SERS) with high field enhancement.

Precise Morphology Control and Continuous Fabrication of Perovskite Solar Cells Using Droplet-Controllable Electrospray Coating System

Abstract: Herein, we developed a novel electrospray coating system for continuous fabrication of perovskite solar cells with high performance. Our system can systemically control the size of CH3NH3PbI3 precursor droplets by modulating the applied electrical potential, shown to be a crucial factor for the formation of perovskite films. As a result, we have obtained pinhole-free and large grain-sized perovskite solar cells, yielding the best PCE of 13.27% with little photocurrent hysteresis. Furthermore, the average PCE through the continuous coating process was 11.56 ± 0.52%. Our system demonstrates not only the high reproducibility but also a new way to commercialize high-quality perovskite solar cells.

Light-guided electrodeposition of non-noble catalyst patterns for photoelectrochemical hydrogen evolution

Abstract: Hydrogen is in the lime light as a carbon-free alternative energy source due to its high energy conversion efficiency. Solar-driven water splitting is one of the most promising methods for renewable hydrogen production. However, commercialization of a photoelectrochemical hydrogen production system remains a great challenge. One of the emerging concerns is the development of an inexpensive and transparent catalyst, which does not obstruct the light pathways to the semiconductor electrode. Here we report a non-noble metal electrocatalyst for hydrogen evolution, Ni-Mo, which is directly patterned on amorphous Si (a-Si) by light-guided spatially selective electrodeposition without consecutive photolithography processes. A light pattern is illuminated onto the a-Si using a digital micromirror device to commence the photoelectrochemical deposition. The catalyst patterned by the proposed method not only admits sufficient light to a-Si but also enables long distance carrier transport along the inversion layer, as previously observed in crystalline Si (c-Si) photocathodes. This new electrodeposition method enables mask-free patterning on a-Si and is expected to expedite a lower cost, more efficient, and self-biasing integrated photoelectrochemical water-splitting device.

Scalable fabrication of perovskite solar cells

Abstract: Perovskite materials use earth-abundant elements, have low formation energies for deposition and are compatible with roll-to-roll and other high-volume manufacturing techniques. These features make perovskite solar cells (PSCs) suitable for terawatt-scale energy production with low production costs and low capital expenditure. Demonstrations of performance comparable to that of other thin-film photovoltaics (PVs) and improvements in laboratory-scale cell stability have recently made scale up of this PV technology an intense area of research focus. Here, we review recent progress and challenges in scaling up PSCs and related efforts to enable the terawatt-scale manufacturing and deployment of this PV technology. We discuss common device and module architectures, scalable deposition methods and progress in the scalable deposition of perovskite and charge-transport layers. We also provide an overview of device and module stability, module-level characterization techniques and techno-economic analyses of perovskite PV modules. Perovskite solar cells (PSCs) have emerged as a revolutionary class of photovoltaic technology. Here, we review recent progress and challenges in scaling up PSCs towards commercialization. We discuss several areas, including device architectures, deposition methods, scalable deposition of perovskite and charge transport layers, device stability, module-level characterization and techno-economic analyses.

Nanometals for Solar-to-Chemical Energy Conversion: From Semiconductor-Based Photocatalysis to Plasmon-Mediated Photocatalysis and Photo-Thermocatalysis.

Abstract: Nanometal materials play very important roles in solar-to-chemical energy conversion due to their unique catalytic and optical characteristics They have found wide applications from semiconductor photocatalysis to rapidly growing surface plasmon-mediated heterogeneous catalysis The recent research achievements of nanometals are reviewed here, with regard to applications in semiconductor photocatalysis, plasmonic photocatalysis, and plasmonic photo-thermocatalysis As the first important topic discussed here, the latest progress in the design of nanometal cocatalysts and their applications in semiconductor photocatalysis are introduced Then, plasmonic photocatalysis and plasmonic photo-thermocatalysis are discussed A better understanding of electron-driven and temperature-driven catalytic behaviors over plasmonic nanometals is helpful to bridge the present gap between the communities of photocatalysis and conventional catalysis controlled by temperature The objective here is to provide instructive information on how to take the advantages of the unique functions of nanometals in different types of catalytic processes to improve the efficiency of solar-energy utilization for more practical artificial photosynthesis

Interfacial Materials for Organic Solar Cells: Recent Advances and Perspectives.

Abstract: Organic solar cells (OSCs) have shown great promise as low-cost photovoltaic devices for solar energy conversion over the past decade. Interfacial engineering provides a powerful strategy to enhance efficiency and stability of OSCs. With the rapid advances of interface layer materials and active layer materials, power conversion efficiencies (PCEs) of both single-junction and tandem OSCs have exceeded a landmark value of 10%. This review summarizes the latest advances in interfacial layers for single-junction and tandem OSCs. Electron or hole transporting materials, including metal oxides, polymers/small-molecules, metals and metal salts/complexes, carbon-based materials, organic-inorganic hybrids/composites, and other emerging materials, are systemically presented as cathode and anode interface layers for high performance OSCs. Meanwhile, incorporating these electron-transporting and hole-transporting layer materials as building blocks, a variety of interconnecting layers for conventional or inverted tandem OSCs are comprehensively discussed, along with their functions to bridge the difference between adjacent subcells. By analyzing the structure–property relationships of various interfacial materials, the important design rules for such materials towards high efficiency and stable OSCs are highlighted. Finally, we present a brief summary as well as some perspectives to help researchers understand the current challenges and opportunities in this emerging area of research.

Photoelectrocatalytic Materials for Solar Water Splitting

Abstract: The generation of fuels and chemicals from sunlight offers a promising approach for the storage of solar energy. Natural photosynthesis is the best-known example for converting solar energy into chemical energy. In the light-dependent reactions of photosynthesis, the photoinduced electron transport chain from water (H2O) to reduced nicotinamide adenine dinucleotide phosphate (NADPH) is a kind of Z-scheme energetics diagram, which involves two photoexcitation steps and a downhill electron flow from photosystem II (PSII) to photosystem I (PSI) (Figure 1). The Z-scheme pathway is advantageous in realizing efficient charge separation and producing active species with strong reducibility for subsequent reduction of CO2 to hydrocarbons. In practice, artificial photosynthesis is an alternative approach to generate hydrogen energy using sunlight to split Photoelectrocatalytic water splitting offers a promising approach to convert sunlight into sustainable hydrogen energy. A thorough understanding of the relationships between the properties and functions of photoelectrocatalytic materials plays a crucial role in the design and fabrication of efficient photoelectrochemical systems for water splitting. This review presents the advances in the development of efficient photoelectrocatalytic materials. First, the fundamentals involved in the photoelectrocatalytic water splitting are elaborated. Then, the critical properties of photoelectrocatalytic materials are classified and discussed according to the associated photoelectrochemical processes, including light absorption, charge separation, charge transportation, and photoelectrocatalytic reactions. The importance of heterointerfaces in photoelectrodes is also mentioned in conjunction with the illustration of some functional interlayer materials. Finally, some strategies that can be employed in material screening and optimization for the construction of highly efficient photoelectrochemical devices for water splitting are also discussed. Water Splitting