연구소식

우수한 결정성을 나타내는 이중 페로브스카이트 할라이드 단결정의 설계 및 구현 [Journal of Materiomics (2020) 등재]
2021-11-24
유럽을 중심으로 위험물질 사용제한 지침 (Restricting the use of Hazardous Substances, RoHS)에서는 Pb 사용을 엄격히 제한하고 있으며, 이러한 친환경 소재 정책은 전 세계적으로 확산되고 있다. 최근, 광전자 소재/소자 분야에서는 지난 10여 년간 활발히 연구되어 온 유연계 하이브리드 페로브스카이트 할라이드 소재를 대체할 수 있는 신물질 찾고 있으며, 그 후보 신물질로써 이중 페로브스카이트 구조를 가지고 있는 무연계 할라이드 소재가 주목받고 있다. 본 연구에서는 수열합성법을 이용하여 이중 페로브스카이트 할라이드 내부의 휘발성이 있는 Bi 원소와 높은 이온 이동성이 있는 Ag 원소의 함량비를 조절하면서, 고품질의 할라이드 단결정이 합성될 수 있는 최적의 조건을 조사하였다. 주사터널전자현미경과 같은 첨단 실험측정 기법을 사용하여 성장된 이중 페로브스카이트 할라이드 단걸정 내부의 원소 배열 상태나 결정구조를 원자 수준에서 가시화하고, 관련 광학적, 전기적 특성을 연구하였다. 그 결과, Ag 이온이 풍부한 화학적 환경에서 합성된 할라이드 단결정에서 상대적으로 적은 결함 밀도와 높은 정공 이동성을 관측할 수 있었다. 본 연구 결과는 우수한 광전자 효율을 나타내는 무연계 할라이드 소재/소자를 구현하는 데에 응용될 수 있다. (본 연구 성과는 저널 표지로 선정됨.) - 고품질 할라이드 페로브스카이트 단결정 (halide perovskite single crystals) 성장- Highly ordered lead-free double perovskite halides by design, J. Materiomics 6, 651 (2020). [cover page]- 할라이드 페로브스카이트 단결정, J. Korean Inst. Electr. Electron. Mater. Eng. 34, 283 (2021). [총설논문]

고전련 에너지 스토리지 커페시터
2021-11-24
- 무연계(Pb-free) 이완형 강유전체(relaxor-ferroelectric) 소재를 이용한 고전력 에너지 스토리지 커페시터 개발'Thermally-stable high energy-storage performance over a wide temperature range in relaxor-ferroelectric Bi1/2Na1/2TiO3-based ceramics', Ceram. Inter. 47, 23488 (2021).DOI : 10.1016/j.ceramint.2021.05.065 AbstractIn this study, lead-free zirconium (Zr)-modified Bi1/2(Na0.78K0.22)1/2TiO3 (BNKT) ceramics were synthesized by the conventional solid-state reaction method. The co-existence of two phases (tetragonal; P4mm and cubic phases; Pmm) with definite phase fractions were observed for all samples. The lattice parameters were gradually enhanced by the addition of Zr-content in the BNKT ceramics, which strongly support the relaxor-ferroelectric response. All of the samples are well-dense with no noticeable pores detected. Definite grains with clear grain boundaries were observed through SEM analysis. The temperature-dependent (25?200 °C) ferroelectric polarization response of all specimens were studied in detail under the constant applied electric field (60 kV cm-1). Thermally-stable high energy-storage properties (Wrec ? 0.72 J cm-3, and η ? 98%) with an extended operating temperature range (25?200 °C) within ±15% variation was observed for the Zr-modified BNKT composition. The enhancement of energy-storage properties can be attributed to the Zr addition, which increased the phase fraction of cubic crystal structure and assisted the ferroelectric to relaxor-ferroelectric phase transition. This study provides a comprehensive analysis of the energy-storage response of the lead-free ceramics for energy-storage devices.

산할로겐화 페로브스카이트 강유전체
2021-11-24
- 산할로겐화 페로브스카이트(oxychalcogenide perovskites) 강유전체 합성 실현- Enhanced ferroelectricity in perovskite oxysulfides, Phy. Rev. Mater. 3, 084405 (2019). - 이종-음이온화 신소재: 산칼코겐화 페로브스카이트, New Phys.: Sae Mulli 71, (2021). [12월 출판 예정, 총설논문]- 화학적 용해법에 기반한 황이온 치환 기술, 대한민국 특허, 제 10-2137238호.

Cu도핑을 통한 In/Cu:ZnS 양자점 합성법 개발 및 광화학적 수소생성 반응 활용
2021-11-24
Cu도핑을 통한 In/Cu:ZnS 양자점 합성법 개발 및 광화학적 수소생성 반응 활용'Controlled Photoinduced Electron Transfer from InP/ZnS Quantum Dots through Cu Doping: A New Prototype for the Visible-Light Photocatalytic Hydrogen Evolution Reaction', Nano Letters, 20, 6263-6271(2020)DOI : 10.1021/acs.nanolett.0c00983 AbstractPhotoexcited electron extraction from semiconductors can be useful for converting solar energy into useful forms of energy. Although InP quantum dots (QDs) are considered alternative materials for solar energy conversion, the inherent instability of bare InP QDs demands the use of passivation layers such as ZnS for practical applications, which impedes carrier extraction from the QDs. Here, we demonstrate that Cu-doped InP/ZnS (InP/Cu:ZnS) QDs improve the electron transfer ability due to hole capture by Cu dopants. Steady-state and time-resolved photoluminescence studies confirmed that electrons were effectively transferred from the InP/Cu:ZnS QDs to a benzoquinone acceptor by retarding the electron?hole recombination within the QD. We evaluated the photocatalytic H2 evolution performance of InP/Cu:ZnS QDs under visible light, which showed outstanding photocatalytic H2 evolution activity and stability under visible light illumination. The photocatalytic activity was preserved even in the absence of a cocatalyst.

[경상일보] 울산대, 주인-손님 상호작용 이용한 ‘핫전자’ 조절법 개발
2021-11-24
기사 원문 : http://www.ksilbo.co.kr/news/articleView.html?idxno=900161

In situ reversible tuning of chemical interface damping in single
2021-11-24
In situ reversible tuning of chemical interface damping in single gold nanorod-based recyclable platforms through manipulation of supramolecular host?guest interactions, Chemical Science, 12, 7115 to 7124 (2021)DOI : 10.1039/d1sc01204eAbstractRecently, chemical interface damping (CID) has been proposed as a new plasmon damping pathway based on interfacial hot-electron transfer from metal to adsorbate molecules. It has been considered essential, owing to its potential implications in efficient photochemical processes and sensing experiments. However, thus far, studies focusing on controlling CID in single gold nanoparticles have been very limited, and in situ reversible tuning has remained a considerable challenge. In these scanning electron microscopy-correlated dark-field spectroscopic measurements and density functional theory calculations, cucurbit[7]uril (CB[7])-based host?guest supramolecular interactions were employed to examine and control the CID process using monoamine-functionalized CB[7] (CB[7]-NH2) attached to single gold nanorods (AuNRs). In situ tuning of CID through the CB[7]?oxaliplatin complexation, which can result in the variation of the chemical nature and electronic properties of adsorbates, was presented. In addition, in situ tuning of CID was demonstrated through the competitive release of the oxaliplatin guest from the oxaliplatin@CB[7] complex, which was then replaced by a competitor guest of spermine in sufficient amounts. Furthermore, nuclear magnetic resonance experiments confirmed that the release of the guest is the consequence of adding salt (NaCl). Thus, in situ reversible tuning of CID in single AuNRs was achieved through successive steps of encapsulation and release of the guest on the same AuNR in a flow cell. Finally, single CB[7]-NH2@AuNRs were presented as a recyclable platform for CID investigations after the complete release of guest molecules from their host?guest inclusion complexes. Therefore, this study has paved a new route to achieve in situ reversible tuning of CID in the same AuNR and to investigate the CID process using CB-based host?guest chemistry with various guest molecules in single AuNRs for efficient hot-electron photochemistry and biosensing applications.

Interface Defect Engineering of MoS2Monolayer: Interface Defect Engineering of a Large Scale CVD Grown MoS2Monolayer via Residual Sodium at the SiO2/Si Substrate
2021-11-24
- NaCl 촉매제를 이용한 화학기상증착법으로 성장한 대면적 균일한 단일층 n-형 MoS2의 아래층 황원자 공극의 결함들을 SiO2 기판에 잔류하는 Na 양이온을 전기적으로 이동하여 치유하는 결과를 출간하였다. Interface Defect Engineering of MoS2Monolayer: Interface Defect Engineering of a Large?Scale CVD?Grown MoS2Monolayer via Residual Sodium at the SiO2/Si Substrate, Advanced Materials Interfaces, 8, 2170080 (2021)DOI : 10.1002/admi.202170080 AbstractIn article number 2100428, Sang Wook Han, Soon Cheol Hong, and co-workers uncover that the residual Na cations at the SiO2 substrate during a NaCl-assisted chemical vapor deposition-growth process induce the n-type doping into the large-scale supported uniform MoS2 monolayer. Furthermore, the residual Na cations are electrically moved toward the bottom side of the MoS2 monolayer to cure the interfacial sulfur vacancy defects.