Random Conjugated Copolymers for Efficient Organic Photovoltaics

Taeshik Earmme(엄태식) 한국고분자학회 2019 한국고분자학회 학술대회 연구논문 초록집 Vol.44 No.1

[특집에부쳐] 고분자 복합재료

엄태식(Taeshik Earmme),이승애(Seungae Lee) 한국고분자학회 2020 고분자 과학과 기술 Vol.31 No.6

Polyurethane triblock copolymer gate dielectrics for low-voltage organic thin-film transistors

김동규,김충익,Taeshik Earmme 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.71 No.-

Novel polyurethane triblock copolymers comprising polycaprolactone diol (PCL), 1,6-hexamethylene diisocyanate (HMDI), and polyethylene glycol (PEG) were synthesized for use as gate dielectric for organic thin-film transistors (OTFTs). Thin films of polyurethane gate dielectrics processed from solution exhibit excellent insulating properties (∼7 × 10−7 A/cm2 at 1 V) as well as large areal capacitance (170 nF/cm2) with film thickness of ∼50 nm. OTFTs are fabricated with representative n-channel organic semiconductor (N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide; PTCDI-C13) using the developed gate dielectrics, and the resulting devices show decent electrical performance with negligible hysteresis at low operating voltage of 1 V.

Polyurethane triblock copolymer gate dielectrics for low-voltage organic thin-film transistors

Kim, Dongkyu,Kim, Choongik,Earmme, Taeshik Elsevier 2019 Journal of industrial and engineering chemistry Vol.71 No.-

<P><B>Abstract</B></P> <P>Novel polyurethane triblock copolymers comprising polycaprolactone diol (PCL), 1,6-hexamethylene diisocyanate (HMDI), and polyethylene glycol (PEG) were synthesized for use as gate dielectric for organic thin-film transistors (OTFTs). Thin films of polyurethane gate dielectrics processed from solution exhibit excellent insulating properties (∼7×10<SUP>−7</SUP> A/cm<SUP>2</SUP> at 1V) as well as large areal capacitance (170nF/cm<SUP>2</SUP>) with film thickness of ∼50nm. OTFTs are fabricated with representative n-channel organic semiconductor (N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide; PTCDI-C13) using the developed gate dielectrics, and the resulting devices show decent electrical performance with negligible hysteresis at low operating voltage of 1V.</P>

Implementation Strategy for the Numerical Efficiency Improvement of the Multiscale Interpolation Wavelet-Galerkin Method

Jeong Hun Seo,Taemin Earmme,Gang-Won Jang,Yoon Young Kim 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.1

The multiscale wavelet-Galerkin method implemented in an adaptive manner has an advantage of obtaining accurate solutions with a substantially reduced number of interpolation points. The method is becoming popular, but its numerical efficiency still needs improvement. The objectives of this investigation are to present a new numerical scheme to improve the performance of the multi scale adaptive wavelet-Galerkin method and to give detailed implementation procedure. Specifically, the subdomain technique suitable for multiscale methods is developed and implemented. When the standard wavelet-Galerkin method is implemented without domain subdivision, the interaction between very long scale wavelets and very short scale wavelets leads to a poorly-sparse system matrix, which considerably worsens numerical efficiency for large- sized problems. The performance of the developed strategy is checked in terms of numerical costs such as the CPU time and memory size. Since the detailed implementation procedure including preprocessing and stiffness matrix construction is given, researchers having experiences in standard finite element implementation may be able to extend the multiscale method further or utilize some features of the multiscale method in their own applications.

Effect of end-block chain length on rheological properties of ABA triblock copolymer hydrogels

Hyunjoon Jung,Taeshik Earmme,Soo-Hyung Choi 한국유변학회 2021 Korea-Australia rheology journal Vol.33 No.2

End-block length dependence of the hydrogel relaxation dynamics was investigated using PEO-based ABA triblock copolymer solutions in an aqueous solvent. Both ends of PEO were capped with hydrophobic poly(isopropyl glycidyl ether-co-ethyl glycidyl ether) exhibiting a lower critical solution temperature (LCST) behavior, resulting in the transition between sol and gel with temperature. Despite the nearly identical hydrophobicity of the end-blocks, the sol-to-gel transition temperature is found to be significantly dependent on the end-block length. Particularly, a small increment of the end-block length leads to significantly slower relaxation dynamics which is attributed to the thermodynamic barrier of end-block extraction. Hydrogels with an appropriate relaxation time show excellent injectability and self-healing ability, yet extremely slow relaxation dynamics result in brittle hydrogels. These results are discussed in terms of current understanding of the hydrogel relaxation dynamics and particular attention is paid to the issue of the chain dynamics between aggregated cores.

석출물이 탄성변형과 탄성변형 에너지

이종길,Johnson, William C.,엄윤용 대한금속재료학회(대한금속학회) 1978 대한금속·재료학회지 Vol.16 No.5

석출물과 관련되는 탄성변형과 탄성변형에너지를 요약 재검토하였다. 약 20년 전에 Eshelby의 획기적인 연구 결과가 발표된 후 이 문제에 관한 많은 진보가, 특히 이방성결정체를 중심으로 이루어져 왔다. 제일 먼저 이방성 결정고체내에 함유되고 있는 타원형의 석출물과 관련되는 탄성변형 에너지를 몇개의 대표적인 결과를 예를 들어 검토하고, 다음으로 정육면체와 같은 다른 형상을 갖는 석출물의 탄성변형이 어떻게 다른가를 고찰하였다. 두개의 구형상 석출물간에 작용하는 에너지를 실험적으로 관찰되고 있는 석출물의 질서적인 배열형상과 비교 논의하였다. 마지막으로 핵형성과정에서 어떻게 탄성변형 에너지가 영향을 주는가와 탄성변형이 소성적으로 이완이 가능할 때 어떻게 달라지는가를 검토하였다. The elastic strains and strain energies associated with precipitates are reviewed. Since the classical works of Eshelby were published almost two decades ago. there has been a rapid progress in understanding this interesting problem, especially in the anisotropic case. The elastic strain energy of inhomogenous ellipsoidal precipitates in anisotropic crystalline solids is discussed with some representative numerical results. The nature of the elastic strains associated with a non-ellipsoidal precipitate such as a cuboid is also described. The elastic interaction energy of two spherical precipitates in an anisotropic matrix is discussed in connection with some experimental observations of precipitate alignments. Finally, some of the results are applied to the homogeneous nucleation theory and plastic relaxation of the transformation stress is also briefly discussed.

Implementation Strategy for the Numerical Efficiency Improvement of the Multiscale Interpolation Wavelet-Galerkin Method

Seo Jeong Hun,Earmme Taemin,Jang Gang-Won,Kim Yoon Young The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.1

The multi scale wavelet-Galerkin method implemented in an adaptive manner has an advantage of obtaining accurate solutions with a substantially reduced number of interpolation points. The method is becoming popular, but its numerical efficiency still needs improvement. The objectives of this investigation are to present a new numerical scheme to improve the performance of the multi scale adaptive wavelet-Galerkin method and to give detailed implementation procedure. Specifically, the subdomain technique suitable for multiscale methods is developed and implemented. When the standard wavelet-Galerkin method is implemented without domain subdivision, the interaction between very long scale wavelets and very short scale wavelets leads to a poorly-sparse system matrix, which considerably worsens numerical efficiency for large-sized problems. The performance of the developed strategy is checked in terms of numerical costs such as the CPU time and memory size. Since the detailed implementation procedure including preprocessing and stiffness matrix construction is given, researchers having experiences in standard finite element implementation may be able to extend the multi scale method further or utilize some features of the multiscale method in their own applications.

A study on the thermomechanical behavior of semiconductor chips on thin silicon substrate

임재혁,한만희,이준연,Youn Young Earmme,이순복,임세영 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.8

This study is concerned with the deformation or warping behavior of thin layered semiconductor structure comprising a silicon substrate, a pattern layer and a polyimide coating layer with its thickness varying from 100um to 50 um. In contrast with the conventional thick semiconductor structure, today’s semiconductor structure is increasingly thin and therefore the warping is extremely conspicuous, being among the major concerns in the structural design of a chip. In the view of thermomechanical analysis of an extremely thin layer structure considered in the present paper, a few parameters on the deformation should be taken into consideration such as the pattern layer and intrinsic stress. To account for the effect of the pattern layer, we make a well educated guess for the mechanical properties, employing the test results and the CBA (Composite Beam Analysis) theory. In addition, we take into consideration the effect of the intrinsic stress due to moisture absorption on deformation. We show that the chip warpage is accurately predicted when all these are properly considered. Furthermore, we have found that the local instability or wrinkling, associated with the nonuniformity or the inhomogeneity in material properties and bonding quality between any two neighboring layers, appears as one important mode of energy relaxation in addition to the overall warpage when the chip thickness becomes very small.

Analysis of vertical cracking phenomena in tensile-strained epitaxial film on a substrate: Part I. Mathematical formulation

Lee, S.,Choi, S.T.,Earmme, Y.Y. Elsevier 2006 International journal of solids and structures Vol.43 No.11-12

<P><B>Abstract</B></P><P>This paper presents an analysis of a single vertical crack and periodically distributed vertical cracks in an epitaxial film on a semi-infinite substrate where the cracks penetrate into the substrate. The film and substrate materials have different anisotropic elastic constants, necessitating Stroh formalism in the analysis. The misfit strain due to the lattice mismatch between the film and the substrate serves as the driving force for crack formation. The solution for a dislocation in an anisotropic trimaterial is used as a Green function, so that the cracks are modeled as the continuous distributions of dislocations to yield the singular integral equations of Cauchy-type. The Gauss–Chebyshev quadrature formula is adopted to solve the singular integral equations numerically. Energy arguments provide the critical condition for crack formation, at which the cracks are energetically favorable configurations, in terms of the ratio of the penetration depth into the substrate to the film thickness, the ratio of the spacing of the periodic cracks to the film thickness, and the generalized Dundurs parameters between the film and substrate materials.</P>