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3. Polymer Materials for Optoelectronics and Energy Applications.

Author

Lim, Ju Won

Subjects
*FLUORESCENCE resonance energy transfer, *OPTOELECTRONIC devices, *LIGHT emitting diodes, *PHOTOVOLTAIC cells, *TECHNOLOGICAL innovations
Abstract

This review comprehensively addresses the developments and applications of polymer materials in optoelectronics. Especially, this review introduces how the materials absorb, emit, and transfer charges, including the exciton–vibrational coupling, nonradiative and radiative processes, Förster Resonance Energy Transfer (FRET), and energy dynamics. Furthermore, it outlines charge trapping and recombination in the materials and draws the corresponding practical implications. The following section focuses on the practical application of organic materials in optoelectronics devices and highlights the detailed structure, operational principle, and performance metrics of organic photovoltaic cells (OPVs), organic light-emitting diodes (OLEDs), organic photodetectors, and organic transistors in detail. Finally, this study underscores the transformative impact of organic materials on the evolution of optoelectronics, providing a comprehensive understanding of their properties, mechanisms, and diverse applications that contribute to advancing innovative technologies in the field. [ABSTRACT FROM AUTHOR]

Published
2024
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34. Calorimetric Systems to Explore Radiative Thermal Transport and the Thermodynamics of Hydrogen (H2) Reactions for Energy Utilization

Author

Lim, Ju Won

Subjects
Calorimetric Systems, Radiative Thermal Transport, Energy Utilization, Thermodynamics of Hydrogen
Abstract

Thermal radiation plays a crucial role in various technological applications, ranging from thermal energy conversion devices to the manufacturing of electronic devices. In this dissertation, I discuss how nanoscale thermal radiation can be controlled via thin films and how phase transitions in thin films can be employed to control the flow of heat. Moreover, I describe how novel calorimetric tools can be developed to probe the thermodynamics of chemical reactions with nanomaterials. In Chapter 1, prior to presenting my research, I delve into background material covering the quantification of heat flow in calorimetry, conceptual discussions regarding the blackbody limit, hydrogenation reactions of transition metals, and related topics. In Chapter 2, I outline how I developed a photonic thermal transistor comprising a source-drain device (hot and cold electrodes) and a vanadium oxide-based planar gate electrode, whose dielectric properties can be adjusted by changing its temperature. I demonstrate that when the gate, located near (< ~1 µm) the source-drain device, undergoes a metal-insulator transition, the radiative heat transfer between the source and drain changes by a factor of three. These findings are supported by detailed calculations that highlight the mechanism of thermal modulation. Furthermore, I show that this photonic thermal transistor features a much faster switching time (~500 ms as opposed to minutes) due to the small thermal mass of the nanoscale devices employed in the work. The advances described here are expected to open new opportunities for designing photonic thermal circuits or computing systems for advanced thermal management. In Chapter 3, I present my exploration of radiative heat transfer (RHT) between objects separated by nanometer-sized vacuum gaps to measure the thickness-dependence of RHT between planar nanofilms. This phenomenon is remarkably distinct from far-field thermal radiation and can exceed the blackbody radiation limit by orders of magnitude. I report direct measurements of the thickness-dependence of RHT between two planar magnesium fluoride nanofilms (thickness ranging from 20 to 500 nm) performed using microfabricated devices and a custom-developed nanopositioner. These results directly demonstrate, for the first time, that nanofilms have the capability to enhance thermal radiation by up to 800 times beyond the blackbody limit. Moreover, they prove to be as effective as bulk materials when the dimensions of the nanoscale gaps are smaller than the thickness of the nanofilm. In Chapter 4, I describe the construction of a calorimetric system with a resolution of

Published
2024

42. Plasmonic Periodic Nanodot Arrays viaLaser Interference Lithography for Organic Photovoltaic Cells with >10% Efficiency

Author

Oh, Yulin, Lim, Ju Won, Kim, Jae Geun, Wang, Huan, Kang, Byung-Hyun, Park, Young Wook, Kim, Heejun, Jang, Yu Jin, Kim, Jihyeon, Kim, Dong Ha, and Ju, Byeong-Kwon

Abstract

In this study, we demonstrate a viable and promising optical engineering technique enabling the development of high-performance plasmonic organic photovoltaic devices. Laser interference lithography was explored to fabricate metal nanodot (MND) arrays with elaborately controlled dot size as well as periodicity, allowing spectral overlap between the absorption range of the active layers and the surface plasmon band of MND arrays. MND arrays with ∼91 nm dot size and ∼202 nm periodicity embedded in a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) hole transport layer remarkably enhanced the average power conversion efficiency (PCE) from 7.52% up to 10.11%, representing one of the highest PCE and degree of enhancement (∼34.4%) levels compared to the pristine device among plasmonic organic photovoltaics reported to date. The plasmonic enhancement mechanism was investigated by both optical and electrical analyses using finite difference time domain simulation and conductive atomic force microscopy studies.

Published
2024
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48. High-Performance UV-Vis-NIR Phototransistors Based on Single-Crystalline Organic Semiconductor-Gold Hybrid Nanomaterials.

Author

Jung, Ji Hyung, Yoon, Min Ji, Lim, Ju Won, Lee, Yoon Ho, Lee, Kang Eun, Kim, Dong Ha, and Oh, Joon Hak

Subjects
OPTOELECTRONIC devices, MATERIALS, NANOSTRUCTURED materials, GOLD nanoparticles, PHOTOTRANSISTORS, INFRARED sources, ACTION spectrum
Abstract

Hybrid materials in optoelectronic devices can generate new functionality or provide synergistic effects that enhance the properties of each component. Here, high-performance phototransistors with broad spectral responsivity in UV-vis-near-infrared (NIR) regions, using gold nanorods (Au NRs)-decorated n-type organic semiconductor and N, N′-bis(2-phenylethyl)-perylene-3,4:9,10-tetracarboxylic diimide (BPE-PTCDI) nanowires (NWs) are reported. By way of the synergistic effect of the excellent photo-conducting characteristics of single-crystalline BPE-PTCDI NW and the light scattering and localized surface plasmon resonances (LSPR) of Au NRs, the hybrid system provides new photo-detectivity in the NIR spectral region. In the UV-vis region, hybrid nanomaterial-based phototransistors exhibit significantly enhanced photo-responsive properties with a photo-responsivity ( R) of 7.70 × 105 A W−1 and external quantum efficiency (EQE) of 1.42 × 108% at the minimum light intensity of 2.5 µW cm−2, which are at least tenfold greater than those of pristine BPE-PTCDI NW-based ones and comparable to those of high-performance inorganic material-based devices. While a pristine BPE-PTCDI NW-based photodetector is insensitive to the NIR spectral region, the hybrid NW-based phototransistor shows an R of 10.7 A W−1 and EQE of 1.35 × 103% under 980 nm wavelength-NIR illumination. This work demonstrates a viable approach to high-performance photo-detecting systems with broad spectral responsivity. [ABSTRACT FROM AUTHOR]

Published
2017
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50. Highly transparent ZTO/Ag/ZTO multilayer electrode deposited by inline sputtering process for organic photovoltaic cells

Author

Cho, Se-Hee, primary, Pandey, Rina, additional, Wie, Chang-Hwan, additional, Lee, Yun Jae, additional, Lim, Ju-Won, additional, Park, Dong-Hee, additional, Seok, Jee-Soo, additional, Jang, Yoon-Hee, additional, Kim, Kyung-Kon, additional, Hwang, Do Kyung, additional, Byun, Dong-Jin, additional, and Choi, Won-Kook, additional

Published
2014
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