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486 results on '"Lee, Jung-Yong"'

1. Establishing Co‐Continuous Network of Conjugated Polymers and Elastomers for High‐Performance Polymer Solar Cells with Extreme Stretchability

Author

Lee, Jin‐Woo, Nguyen, Trieu Hoang‐Quan, Oh, Eun Sung, Lee, Seungbok, Choi, Jaeyoung, Kwon, Hyun Soo, Wang, Cheng, Lee, Seungjin, Lee, Jung‐Yong, Kim, Taek‐Soo, and Kim, Bumjoon J

Subjects
Engineering, Macromolecular and Materials Chemistry, Materials Engineering, Chemical Sciences, elastomer, intrinsically stretchable organic solar cells, mechanical robustness, polymer solar cells, stretchability, Interdisciplinary Engineering, Macromolecular and materials chemistry, Materials engineering
Abstract

High power conversion efficiency (PCE) and mechanical robustness are prerequisites for wearable applications of organic solar cells (OSCs). However, stretchability of present active systems (i.e., crack-onset strain (COS) < 30%) should be improved. While introducing elastomers into active systems is considered a simple method for improving stretchability, the inclusion of elastomers typically results in a decrease in PCE of the OSC with a limited enhancement in the stretchability due to lack of interconnected electrical and mechanical pathways. In this study, it is developed efficient and intrinsically stretchable (IS)-OSCs with exceptional mechanical robustness, by constructing co-continuous networks of conjugated polymers (D18) and elastomers (SEBS) within active layers. It is demonstrated that the blend film with a specific ratio (40:60 w/w) of D18:SEBS is crucial for forming co-continuous structures, establishing well-connected mechanical and electrical channels. Consequently, D180.4:SEBS0.6/L8-BO OSCs achieve 16-times higher stretchability (COS = 126%) than the OSCs based on D18/L8-BO (COS = 8%), while achieving 4-times higher PCE (12.13%) compared to the OSCs based on SEBS-rich active layers (D180.2:SEBS0.8/L8-BO, PCE = 3.15%). Furthermore, D180.4:SEBS0.6-based IS-OSCs preserve 86 and 90% of original PCEs at 50% strain and after 200 stretching/releasing cycles with 15% strain, respectively, demonstrating the highest mechanical robustness among reported IS-OSCs.

Published
2024

2. Wide Effective Work-Function Tuning of Al/SiO$_2$/Si Junction Achieved with Graphene Interlayer at Al/SiO$_2$ Interface

Author

Song, Wonho, Lee, Jung-Yong, Kim, Junhyung, Park, Jinyoung, Jo, Jaehyeong, Hyun, Eunseok, Kim, Jiwan, Eom, Daejin, Choi, Gahyun, and Park, Kibog

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The effective work-function of metal electrode is one of the major factors to determine the threshold voltage of metal/oxide/semiconductor junction. In this work, we demonstrate experimentally that the effective work-function of Aluminum (Al) electrode in Al/SiO$_2$/n-Si junction increases significantly by $\sim$1.04 eV with the graphene interlayer inserted at Al/SiO$_2$ interface. We also provide the device-physical analysis of solving Poisson equation when the flat-band voltage is applied to the junction, supporting that the wide tuning of Al effective work-function originates from the electrical dipole layer formed by the overlap of electron orbitals between Al and graphene layer. Our work suggests the feasibility of constructing the dual-metal gate CMOS circuitry just by using Al electrodes with area-specific underlying graphene interlayer., Comment: 11 pages, 7 figures

Published
2022

13. Facile Synthesis Route for Halide Perovskite Nanoparticles Using Ultrasonic Spray for Optoelectronic Devices.

Author

Kim, Dong-Jun, Choi, Bongjun, Jeon, Yeonjee, and Lee, Jung-Yong

Abstract

In this paper, we present an efficient and rapid method for synthesizing perovskite nanoparticles (PeNPs) using ultrasonic spray techniques. The synthesized PeNPs are notably larger than the exciton Bohr radius of perovskite, avoiding the quantum confinement effect, and exhibit a size distribution of around 61.6 ± 30 nm. They show an exceptionally narrow full width at half-maximum of approximately 21.8 nm and a high exciton binding energy (Eb) of approximately 204 meV. Furthermore, the physically restrained reprecipitation method not only effectively transforms perovskite precursor droplets into solid PeNPs at the interface of an antisolvent but also concurrently achieves ligand passivation. This dual-action mechanism promotes their dispersion in various organic solvents and highly concentrated solutions, thus significantly expanding the scope of potential optoelectronic applications such as light-emitting diodes and photodetectors. [ABSTRACT FROM AUTHOR]

Published
2024
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16. Design of Star‐Shaped Trimer Acceptors for High‐Performance (Efficiency > 19%), Photostable, and Mechanically Robust Organic Solar Cells

Author

Lee, Jin‐Woo, primary, Sun, Cheng, additional, Lee, Jinho, additional, Kim, Dong Jun, additional, Kang, Won Jung, additional, Lee, Seungbok, additional, Kim, Donguk, additional, Park, Jinseok, additional, Phan, Tan Ngoc‐Lan, additional, Tan, Zhengping, additional, Kim, Felix Sunjoo, additional, Lee, Jung‐Yong, additional, Bao, Xichang, additional, Kim, Taek‐Soo, additional, Kim, Yun‐Hi, additional, and Kim, Bumjoon J., additional

Published
2024
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33. North Korea's arms control policy and the challenge of South Korea's Sunshine policy

Author

Lee, Jung-Yong

Subjects
327.519305195
Abstract

Arms control theory emphasizes the utility of the arms control process – it lessens international hostility and promotes inter-state co-operation.  In the Cold War North Korea adopted a propagandistic and radical arms control policy in order to achieve its key national security strategic objective: the reunification of the Korean peninsula.  In the post-cold War era this arms control approach was totally transformed – North Korean arms control policy became co-operative and pragmatic; focused not on reunification but rather on the sustainability and survival of the regime. This thesis identifies the main tenets of arms control theory and applies them to North Korea (Chapter 2). It characterizes North Korea’s arms control policy during the Cold War (Chapter 3) and notes and accounts for the transformation of arms control orientation and objectives in the post-Cold War era (Chapter 4). The thesis demonstrates the extent of this evolution through an analysis of North Korea’s policy towards key arms control issues (Chapter 5).  It outlines the domestic and foreign influences on North Korean arms control policy.  The specific characteristics of the North Korean leadership and its ruling ideology – the Juche Idea (Chapter 6) is contrasted with an analysis of external determinants, in particular South Korea’s Sunshine Policy (Chapter 7).  The thesis concludes (Chapter 8) by arguing that this study of North Korean arms control policy provides a litmus test or barometer which indicates the orientation and objectives of North Korean national security strategy.  In the post-cold War era North Korean arms control policy has aligned itself with arms control theory, and so this thesis provides a more comprehensive framework within which to understand North Korean foreign and security policy issues and how and why they evolve on the Korean peninsula.

Published
2002

38. Intrinsically Stretchable, Highly Efficient Organic Solar Cells Enabled by Polymer Donors Featuring Hydrogen‐Bonding Spacers (Adv. Mater. 50/2022)

Author

Lee, Jin‐Woo, primary, Seo, Soodeok, additional, Lee, Sun‐Woo, additional, Kim, Geon‐U, additional, Han, Seungseok, additional, Phan, Tan Ngoc‐Lan, additional, Lee, Seungjin, additional, Li, Sheng, additional, Kim, Taek‐Soo, additional, Lee, Jung‐Yong, additional, and Kim, Bumjoon J., additional

Published
2022
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42. Pseudo-bilayered inverted organic solar cells using the Marangoni effect.

Author

Jo, Jihwan, Jeong, Seonju, Lee, Dongchan, Lee, Seungjin, Kim, Bumjoon J., Cho, Shinuk, and Lee, Jung-Yong

Abstract

The randomly mixed morphology of donor and acceptor materials in organic solar cells (OSCs) has been perceived as a breakthrough in the development of OSCs. By contrast, the vertically separated donor and acceptor structures of OSCs allow each material to be optimized separately, which facilitates charge extraction within OSCs and reduces charge recombination. Moreover, the morphological robustness of phase separation in OSCs can enhance their stability. However, sequential solution coating typically requires an orthogonal solvent to prevent the destruction of the bottom layer, and identifying the appropriate solvents is challenging. In addition, a quasi-orthogonal solvent (e.g., volatile solvent) requires a polymer bottom layer that can withstand the solvent during the sequential coating. In this study, we construct a bilayer structure using a small molecule (Y7-BO) as a bottom layer and a polymer (PM6) as a top layer. The PM6 layer is formed on water via the Marangoni phenomenon and directly stamped onto the Y7-BO layer. To develop a pseudo-bilayer (PB) architecture, we incorporate a low-volatility solvent additive into the polymer solution and allow the additive to reside within the bilayer. An appropriately low amount of solvent additive (chloronaphthalene) is added to optimize intermixing at the donor/acceptor interface, which reinforces the face-on molecular orientation of the active layers. Consequently, a power conversion efficiency of 17.12% is achieved by the inverted OSC with a PB architecture, which is higher than that achieved by its bulk heterojunction counterparts. [ABSTRACT FROM AUTHOR]

Published
2023
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