Photon Upconversion Technology

문준혁 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

Photon upconversion is the process of emitting light with wavelengths shorter than the excitation wavelength. Photon upconversion in organic dye pairs is achieved by energy transfer between two molecules (sensitizer and emitter) followed by triplet-triplet annihilation. We introduce a semi-transparent photovoltaic system using photon upconversion. We also introduce the use of upconversion to extend the light harvesting band of water splitting photoelectrodes.

광에너지 상향 전환 기술에 의한 광촉매의 광감응도 향상에 관한 연구

김재혁 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1

광에너지 상향 전환기술(Upconversion, UC)이란, ‘낮은 에너지의 두 개 혹은 그 이상의 광자를 이용해 높은 에너지를 가지는 하나의 광자를 생산해 내는 기술’로 국내 학계에는 아직 생소한 신개념 광에너지 증폭 기술 중 하나이다. 높은 에너지의 광자(짧은 파장)에서 낮은 에너지의 광자(긴 파장)가 생성되는 일반적인 Stokes emission과는 반대로, Upconversion공정은 긴 파장의 광자들을 흡수하여 짧은 파장의 광자를 생성함으로써 Anti-Stokes emission을 발생시킨다. 광자가 흡수되는 대상물질인 광촉매와는 무관하게, 광에너지 자체를 변환시키는 Upconversion 기술은 태양광의 활용도 극대화에 있어 기존과는 다른, 전혀 새로운 접근법을 제시한다. 본 발표에서는 삼중항-삼중항 소멸법에 기반한 Upconversion에 대해 간략히 소개하고, 이를 이용하여 광촉매의 광감응도를 향상시킨 실험적 사례와 그 응용법에 대해 토의한다.

Photon upconversion-assisted luminescence solar concentrators with extended light harvesting for semitransparent photovoltaic systems

김기원,문준혁 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

A luminescent solar concentrator-based photovoltaic system (LSC-PVs) is transparent because it harvests solar light through the LSC, a transparent panel containing only fluorophores. Because of this reason, LSC-PVs is promising as a PV window. Here, we demonstrate an LSC-PVs, which is based on the combination of an upconversion (UC)-assisted dual band harvesting LSC and perovskite solar cells (PSCs) for the practical use of LSC-PV. We arrange a dual LSC panel consisting of a downshift (DS) LSC that convert violet light into red light. The dual LSCs coupled with a PSC exhibit a high average-visible-transmittance (AVT) of 82% and achieve a maximum efficiency of 7.53% at 1 sun (AM 1.5G) illumination. The dual LSC-PSC exhibits a constant efficiency even under oblique solar light illumination and a stable operation with an efficiency retention of 80%.

1P-131 Upconversion Nanocrystal Embedded Mesoporous Carbon-TiO₂ Hybrid Films Enable Enhanced Full-Spectrum Absorption for Superior Solar Light Driven Photocatalysis

권한나,김동하,정경화,장유진 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1

TiO₂ has been mostly used in the photocatalysis due to high activity. However, the large bandgap limits its absorption to UV region, which only possesses 5% of solar energy. Pair of some lanthanides elements can induce long-wavelength radiation and emit shorter wavelength, higher energy radiation by a process called upconversion. Herein β-NaYF₄:Yb³⁺, Tm³⁺, Gd³⁺ UCN embedded in a carbon-doped mesostructured TiO₂ hybrid film were designed using UCN prepared by hydrothermal process, and a triblock copolymer P123, simultaneously acting as a mesoporous template and a carbon source. The photoactivity of novel material was reflected in the degradation of nitrobenzene. The hierarchical mesostructure provides enhanced surface area and improved pore connectivity, facilitating effective charge carrier transfer and efficient mass flow of the reactants. Carbon-doping in the TiO₂ architecture creates a new energy level above the valence band of TiO₂, extending absorption to the visible range.

Er3+/Yb3+-doped CaMoO4 와CaWO4에 첨가된 Li 이온이 Er3+/Yb3+ 상방형광에 미치는 영향

김병국,성삼식,최혜영,김중환 한국물리학회 2013 새물리 Vol.63 No.8

Er3+and Yb3+ co-doped CaWO4 and CaMoO4 polycrystalline powders were prepared by using a solid-state reaction, and their upconversion (UC) luminescence properties were investigated in detail. Under 975-nm laser-diode excitation, the two kinds of powders exhibited strong green UC emission peaks at 530 nm and 550 nm, which were due to the transitions from the 2H11/2 and the 4S3/2 states to the ground state (4I15/2) of the Er3+ ion, respectively. The effects of Li+ doping into CaWO4:Er3+/Yb3+ and CaMoO4:Er3+/Yb3+ were investigated. Introduction of Li+ ions not only promoted crystal growth but also enhanced the UC luminescence intensity by more than two times. This can be attributed to the Li+ ions acting as charge compensators, which modifies the crystal field strength by reducing the lattice constant. 고상반응법으로 Er3+과 Yb3+ 및 Li+이온이 동시에 첨가된 CaMoO4와 CaWO4 형광체를 합성하고, 상방전환 (upconversion:UC)형광을 조사하였다. 불순물 함량에 관계없이 모든 형광체 분말의결정구조는 주 회절 피크 (112)면을 갖는 scheelite 구조였다. 975 nm 레이저 다이오드를 시료에 입사하여 530 nm와 550 nm 중심파장을 갖는강한 녹색 UC 형광이 관찰하였다. 이 형광은 Er3+ 이온의 2H11/2 및 $4S3/2 준위에서 바닥상태 (4I15/2)로천이한 것이다. CaWO4:Er3+/Yb3+와 CaMoO4:Er3+/Yb3+에 Li+ 이온을 첨가함으로써결정소결온도를 낮추었을 뿐 아니라 UC 형광의 세기도 두 배 이상증가시켰다. 이것은 Er3+ 및 Yb3+ 이온이 Ca2+ 자리에치환됨으로써 생기는 양전하 부족을 Li+ 이온이 보상하고 나아가격자상수를 줄임으로서 Er3+ 및 Yb3+이온에 미치는 결정장크기의 변화에 기인한 것으로 판단된다.

Aqueous phase photon upconversion using a post-encapsulation strategy with hollow mesoporous silica microcapsules

이학래,김영환,김성원,방석호,김재혁 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0

We developed new vehicles for aqueous phase photon upconversion using a post-encapsulation strategy with hollow mesoporous silica microcapsules. The prepared silica microcapsules possess tunable diameters, large interior cavities, and ordered radial mesochannels that favor the controlled encapsulation of guest molecules. The upconversion oil is readily encapsulated at high loadings into the microcapsules. We successfully demonstrated cell-mediated triplet-triplet annihilation upconversion system by incorporating our microcapsules with human mesenchymal stem cells, which showed promise system for tumortargeted low-power bioimaging. To the best of our knowledge, this study is the first to design biocompatible triplet-triplet annihilation upconversion system with a post-encapsulation strategy and diverse functionalities, thereby establishing a new and general platform to achieve efficient aqueous phase triplet-triplet annihilation upconversion system for multifunctional applications.

YAG와 YAP 나노형광체에 첨가된 Er(3+) 이온의 상방전환 형광

최혜영,김중환,노현미,양현경,문병기,정중현 한국물리학회 2011 새물리 Vol.61 No.8

수열반응법으로 3 mol%의Er(3+) 이온이 첨가된Y₃(Al_5O_12)(YAG)와 YAlO₃(YAP) 나노형광체를 합성하고, 975nm 다이오드 레이저로 여기하여 녹색과 적색의 상방전환 형광을 얻었다. 그리고 5 ns 펄스폭을 가진 광 파라메틱 발진기로 여기하여Er(3+) 이온의 ^4S_(3/2) 준위에서 발광하는 녹색형광의 시간적거동을 측정하였다. 상방전환 형광은 여기상태흡수(ESA: Excited State Absorption)와 상방향 에너지전달 (ETU: Energy Transfer Upconversion)과정에 기인한다. ESA와 ETU를 도입한 3준위 에너지 모형에대한 율방정식을 실험에서 구한 형광붕괴곡선에 적용하여 나노형광체의자발방출율과 ETU 상수를 구하였다. YAP:Er 나노형광체의 ETU 상수는6,100 s^(-1)로서 YAG:Er의 600 s^(-1)보다 10 배가량 컸다. 이것이YAP에서 발생하는 상방전환 형광의 세기가 YAG:Er의 상방전환 형광에비해 큰 주된 원인이다. Three-mol% Er(3+) ions doped Y₃(Al_5O_12)(YAG) and YAlO₃(YAP) nanophosphors were synthesized using a solvothermal reaction method. Under the excitation of a 975 nm laser diode, the nonophosphors emitted green and red upconversion (UC)photoluminescence. Upon excitation at a wavelength of 975nm with a pulse duration of 5 ns from an optical parametric oscillator, the temporal behavior of the green emission ^4S_(3/2)→^4l_(15/2)transition was measured. Rate equations containing both the excited state absorption (ESA) process and the energy transfer upconversion (ETU) constant were proposed to interpret the upconversion mechanism. The solutions of the rate equations were fitted to the decay curves of the UC green emissions. The ETU constant of YAP:Er was 6,100 s^(1) which is 10 times larger than that of YAG:Er. The ETU process, which results in a larger intensity of the UC emission, is the main mechanism of the UC emission from YAP:Er nanophosphors.

Yb3+ 농도 변화에 따른 Y2O3:Er3+, Yb3+ 나노형광체의 상방전환 형광특성

노현미,오주현,정중현,강하리,김원종,이채현,최용록,박용대,장준규 한국물리학회 2015 새물리 Vol.65 No.7

Y2O3 nanophosphors co-doped with 0.01 mol Er3+ and various concentrations of Yb3+ were synthesized by using the high-energy ball-milling method, and their upconversion properties were studied. The crystallinities and the surface morphologies of the nanophosphors that were investigated by using X-ray diffraction and scanning electron microscopy, respectively, and upconversion luminescence spectra were obtained by using a 975 nm laser diode (LD). According to the Xray diffraction results, as the Yb3+ concentration was increased, the crystallinity of the powder improved, and the powder tended to show a more cubic structure. The emission spectra of the Y2O3:Er3+, Yb3+ nanophosphors showed green, red and blue UC emissions at 550, 660 and 410 nm, which could be assigned to the 2H11/2,4 S3/2 →5 I15/2,4 F9/2 →5 I15/2 and 4G11/2 →5 I15/2 of Er3+ transitions, respectively. Also, their upconversion processes were explained by measuring the pump-power dependency of the upconversion luminescence spectra. Er3+의 농도를 0.01 mol로 고정하고 Yb3+ 농도를 변화시킨 Y2O3:Er3+, Yb3+ 나노형광체를 고에너지 볼 밀링 방법을 이용하여 합성하고 상방전환 형광특성을 연구하였다. X-선 회절실험, 주사전자현미경을 이용하여 합성된 분말의 결정성 및 표면형상을 관찰하고, 975 nm 레이저 다이오드로 여기 하여 상방전환 형광을 얻었다. X-선 회절측정을 통해 합성된 나노형광체는 입방정계 (cubic) 구조임을 확인하였고, Yb3+의 농도가 증가함에 따라 분말의 결정성이 향상됨을 알 수 있었다. 975 nm로 여기 하여 얻은 Y2O3:Er3+, Yb3+ 나노형광체의 발광스펙트럼은 Yb3+의 농도가 증가함에 따라 550 nm 부근의 강한 녹색 형광과 660 nm의 적색 형광, 그리고 약한 410 nm의 청색 형광을 보였으며 이는 각각 Er3+ 이온의 2H11/2, 4S3/2 →5I15/2,4F9/2→5I15/2 그리고 4G11/2 →5I15/2 전이에 기인한다. 또한 상방전환형광의 과정을 형광스펙트럼과 펌프 광 의존도를 측정하여 설명하였다.

Synthesis and Characterization of Folic Acid Labeled Upconversion Fluorescent Nanoprobes for in vitro Cancer Cells Targeted Imaging

Ming Huang,Lijun Wang,Xiaojuan Zhang,Jin Zhou,Lihua Liu,Yuefang Pan,Bin Yu,ZHANGSEN YU 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.5

Upconversion nanoparticles (UCNPs) are widely used in the field of biomedicine, such as biosensing, cell labeling and medical multimodal imaging because of their unique optical properties. In this paper, we demonstrated the synthesis of polyethylenimine-modified NaLuF4:Yb,Er (RE = Lu 0.78, Yb 0.18, Er 0.02) UCNPs in three different solvents, such as water, ethylene glycol and diethylene glycol. The as-prepared UCNPs were characterized and the experimental results showed that the UCNPs synthesized in ethylene glycol had excellent properties. The obtained UCNPs in ethylene glycol had the smallest particle size and uniform size distribution, and the pure cubic phase of crystallization and Dynamic light scattering and particle dispersion index (DLS/Pdi) were the smallest. What's more, the upconversion fluorescence intensity was 7 and 52 times greater than that of UCNPs synthesized in diethylene glycol and water, respectively. In addition, the factors of reaction solvent that had an impact on the particle size, morphology, crystalline phase, DLS and upconversion fluorescence intensity of the synthesized UCNPs were discussed. Moreover, in order to obtain the targeted nanoprobe, we used an EDC/NHS covalent coupling method to modify folic acid to the NaLuF4:Yb,Er/PEI UCNP surface. The NaLuF4:Yb, Er/PEI–FA upconversion fluorescent nanoprobes had low cytotoxicity and were suitable for the application in HeLa cells targeted fluorescent imaging.

Plasmon-enhanced upconversion particles for dye-sensitized solar cells

최정우,이민우,김형모,정주원,전봉현,정대홍,성영은 한국공업화학회 2014 한국공업화학회 연구논문 초록집 Vol.2014 No.1

Upconversion particles (UCPs) have luminescent property that converts a near-infrared extinction into a visible emission. Among these UCPs, the β-NaYF₄ host lattice doped with lanthanide Yb³⁺ and Er³⁺ has been shown to be the most efficient UCP. However, upconversion process generally suffers from low quantum efficiency. Metal nanoparticles such as Ag or Au are known to enhance extinction and emission process by local field amplication and enhancing radiative decay rates. Herein we incorporated the Au decorated β-NaYF₄ into the photoanode of dye-sensitized solar cell. The LSPR effects from Au NPs could enhance the upconversion efficiency. Moreover the light utilization in the photoanode was increased by light scattering and plasmon-enhanced light absorption.