CsPbX$_3$ (X = Br, I) 양자점의 광학적 특성

원하연,김도형 한국물리학회 2018 새물리 Vol.68 No.3

In order to investigate the photoluminescence (PL) and the X-ray excited luminescence (XEL) characteristics of CsPbBr$_3$ and CsPbI$_3$ quantum dots with high effective mass ($Z_{eff}$), we synthesized CsPbBr$_3$ and CsPbI$_3$ quantum dots with a cubic phase by using the wet chemical method. The CsPbBr$_3$ quantum dots had a PL peak at 522 nm and an XEL peak at 537 nm. The CsPbI$_3$ quantum dots had a PL peak at 690 nm and an XEL peak at 711 nm. The high XEL peaks could be attributed to the high $Z_{eff}$ of the CsPbBr$_3$ and the CsPbI$_3$ quantum dots (62.24 and 64.04, respectively). The high $Z_{eff}$ might have led to the high stopping power for X-ray detection. These results show the potential of CsPbBr$_3$ and CsPbI$_3$ quantum dots for applications in the field of optical and X-ray detection. 높은 유효 질량($Z_{eff}$)을 가지는 CsPbBr$_3$와 CsPbI$_3$ 양자점의 광 발광 (photoluminescence, PL) 및 X-선 여기 발광 (X-ray emitted luminescence, XEL) 특성을 확인하기 위해 습식 화학법으로 크기가 각각 5 nm, 8 nm이고 입방 구조를 가지는 CsPbBr$_3$와 CsPbI$_3$ 양자점을 합성하였다. CsPbBr$_3$ 양자점은 522 nm에서 PL피크를, 537 nm에서 XEL 피크를 가지고, CsPbI$_3$ 양자점은 690 nm에서 PL피크를, 711 nm에서 XEL 피크를 가진다. CsPbBr$_3$와 CsPbI$_3$ 양자점의 높은 $Z_{eff}$(각각 62.24, 64.04)는 X-선 검출에 요구되는 높은 정지 전압을 야기하므로, 높은 XEL 스펙트럼 피크를 가지는 CsPbBr$_3$와 CsPbI$_3$ 양자점은 광 검출 및 X-선 검출 분야에 활용 가능성이 있다고 할 수 있다.

열화학기상증착법을 이용한 CsPbBr3 박막 성장 및 특성 연구

김가은,김민진,류혜수,이상현 한국마이크로전자및패키징학회 2023 마이크로전자 및 패키징학회지 Vol.30 No.2

In this study, inorganic perovskite films with different compositions were grown by thermal chemical vapor deposition depending on the substrate and their optical properties were compared. Inorganic perovskite crystals were grown on SiO2/Si and c-Al2O3 substrates using CsBr and PbBr2, respectively, under the same growth conditions. Cs4PbBr6-CsPbBr3 crystallites were grown on the SiO2 with polycrystalline structure, while a CsPbBr3 (100) dominant thin film was formed on the c-Al2O3 substrate with single crystal structure. From the photoluminescence measurement, CsPbBr3 showed typical green emission centered at 534 nm with a full width at half maximum (FWHM) of about 91 meV. The Cs4PbBr6-CsPbBr3 mixed structure exhibits blue-shifted emission at 523 nm with a narrow FWHM of 63 meV and a fast decay time of 6.88 ns. These results are expected to be useful for application in photoelectric devices such as displays, solar cells, and light sensors based on inorganic metal perovskites. 본 연구에서는 열화학기상증착법을 이용한 세슘계 무기 페로브스카이트의 성장기판에 따른 결정 구조의 변화및 광학적 특성을 비교 분석하였다. 무기 페로브스카이트 결정은 CsBr과 PbBr2를 전구체로 사용하여 SiO2/Si와 c-Al2O3 기판 위에 동일한 조건으로 CsPbBr3를 성장하였다. 비정질 구조를 가진 SiO2 표면에서는 Cs4PbBr6-CsPbBr3 혼합상의 결정 입자가 성장하였으며, 단결정 구조인 c-Al2O3 기판에서는 CsPbBr3 (100) 결정 면방향이 우세한 단일상의 박막이 형성되었다. 광학적 분석 결과 CsPbBr3는 약 91 meV의 반치폭을 갖고 약 534 nm 중심의 발광특성을 보였으며, Cs4PbBr6- CsPbBr3 혼합구조에서는 청색 변이에 의해 523 nm의 발광 및 6.88 ns의 빠른 광 소결시간을 확인하였다. 열화학기상증착법을 이용한 페로브스카이트의 결정구조의 제어 및 광특성의 변화는 디스플레이, 태양 전지, 광센서 등 다양한 광전 소자에 적용할 수 있을 것으로 기대된다.

Energy and charge transfer effects for hybrids of perovskite CsPbBr₃ quantum dots on organic semiconducting rubrene nanosheet

Youn, Jongwon,Park, Cheol-Joon,Teng, Xuecheng,Lee, Kwang-Sup,Kim, Jeongyong,Joo, Jinsoo Elsevier 2019 Organic electronics Vol.65 No.-

<P><B>Abstract</B></P> <P>Functionalized perovskite CsPbBr<SUB>3</SUB> quantum dots (CsPbBr<SUB>3</SUB>-QDs) were loaded on the surface of a <I>p</I>-type organic rubrene (5,6,11,12-tetraphenyltetracene) nanosheet (NS) for the fabrication of a new hybrid nano-system. Using a high–resolution laser confocal microscope, the nanoscale photoluminescence (PL) characteristics of the CsPbBr<SUB>3</SUB>-QDs/rubrene-NS hybrids were investigated. We observed a significant enhancement of the PL intensity of the rubrene-NS after the hybridization with the CsPbBr<SUB>3</SUB>-QDs, which originated from the fluorescence resonance energy transfer from the CsPbBr<SUB>3</SUB>-QDs to the rubrene-NS. The PL enhancement ratio varied according to the density of the QDs on the NS. To investigate the hybridization effect with CsPbBr<SUB>3</SUB>-QDs on the electrical characteristics of the rubrene-NS, we fabricated field-effect transistors (FETs) using the pristine and hybrid samples as an active layer. The currents of both FETs using the pristine rubrene-NS and hybrid QDs/rubrene-NS increased with light irradiation through the contribution of photo-excited charges. After the hybridization with the CsPbBr<SUB>3</SUB>-QDs on the rubrene channel, both the electrical current and mobility decreased compared with the pristine rubrene-based FET. This can be explained by the relative decrease of hole concentration in the active channel region near dielectric layer through the interfacial charge transfer between the QDs and the NS, as well as the de-doping effect of the QDs on the rubrene-NS. Thus, we observed the energy and charge transfer effects for the CsPbBr<SUB>3</SUB>-QDs/rubrene-NS hybrids, which can be applied to advanced nanoscale photonics and optoelectronics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Study of PL and charge transport characteristics of rubrene NS and perovskite CsPbBr<SUB>3</SUB>-QDs hybrid. </LI> <LI> Increase of PL intensity of rubrene NS by hybridization with CsPbBr<SUB>3</SUB>-QDs because of energy transfer effect. </LI> <LI> Electrical current and photoresponsivity of rubrene NS decreased due to de-doping effect by the QDs. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The nanoscale photoluminescence and electrical characteristics of organic semiconducting rubrene nanosheet (NS) can be modulated via hybridization with perovskite CsPbBr<SUB>3</SUB>-QDs.</P> <P>[DISPLAY OMISSION]</P>

Efficient and Stable CsPbBr₃ Quantum-Dot Powders Passivated and Encapsulated with a Mixed Silicon Nitride and Silicon Oxide Inorganic Polymer Matrix

Yoon, Hee Chang,Lee, Soyoung,Song, Jae Kyu,Yang, Heesun,Do, Young Rag American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.14

<P>Despite the excellent optical features of fully inorganic cesium lead halide (CsPbX<SUB>3</SUB>) perovskite quantum dots (PeQDs), their unstable nature has limited their use in various optoelectronic devices. To mitigate the instability issues of PeQDs, we demonstrate the roles of dual-silicon nitride and silicon oxide ligands of the polysilazane (PSZ) inorganic polymer to passivate the surface defects and form a barrier layer coated onto green CsPbBr<SUB>3</SUB> QDs to maintain the high photoluminescence quantum yield (PLQY) and improve the environmental stability. The mixed SiN<SUB><I>x</I></SUB>/SiN<SUB><I>x</I></SUB>O<SUB><I>y</I></SUB>/SiO<SUB><I>y</I></SUB> passivated and encapsulated CsPbBr<SUB>3</SUB>/PSZ core/shell composite can be prepared by a simple hydrolysis reaction involving the addition of adding PSZ as a precursor and a slight amount of water into a colloidal CsPbBr<SUB>3</SUB> QD solution. The degree of the moisture-induced hydrolysis reaction of PSZ can affect the compositional ratio of SiN<SUB><I>x</I></SUB>, SiN<SUB><I>x</I></SUB>O<SUB><I>y</I></SUB>, and SiO<SUB><I>y</I></SUB> liganded to the surfaces of the CsPbBr<SUB>3</SUB> QDs to optimize the PLQY and the stability of CsPbBr<SUB>3</SUB>/PSZ core/shell composite, which shows a high PLQY (∼81.7%) with improved thermal, photo, air, and humidity stability as well under coarse conditions where the performance of CsPbBr<SUB>3</SUB> QDs typically deteriorate. To evaluate the suitability of the application of the CsPbBr<SUB>3</SUB>/PSZ powder to down-converted white-light-emitting diodes (DC-WLEDs) as the backlight of a liquid crystal display (LCD), we fabricated an on-package type of tricolor-WLED by mixing the as-synthesized green CsPbBr<SUB>3</SUB>/PSZ composite powder with red K<SUB>2</SUB>SiF<SUB>6</SUB>:Mn<SUP>4+</SUP> phosphor powder and a poly(methyl methacrylate)-encapsulating binder and coating this mixed paste onto a cup-type blue LED. The fabricated WLED show high luminous efficacy of 138.6 lm/W (EQE = 51.4%) and a wide color gamut of 128% and 111% without and with color filters, respectively, at a correlated color temperature of 6762 K.</P> [FIG OMISSION]</BR>

CsPbBr3을 기반으로 한 Perovskite 선량계의 방사선치료 Quality Assurance에 대한 적용가능성 평가

양승우,박성광 한국방사선학회 2022 한국방사선학회 논문지 Vol.16 No.3

In radiation therapy, accurate Quality Assurance (QA) is required to irradiate tumor tissue while minimizing damage to normal tissue. Therefore, a dosimeter that can accurately measure radiation is needed. The purpose of this study is to develop a highly efficient radiation dosimeter with high sensitivity by applying a particle in binder method that can reduce manufacturing costs and simplify processes to perovskite materials that are cheaper and simpler to manufacture. By evaluating the response characteristics to high-energy photon, the applicability of QA dosimeter to radiation therapy was evaluated. As a result of reproducibility evaluation, RSD at 6 MV energy was presented as 1.178% and 15 MV energy was presented as 1.141%. As a result of linearity evaluation according to linear regression analysis, R2 values of 0.9999 were presented under each condition of 6 MV and 15 MV energy. It was found that the CsPbBr3 dosimeter manufactured based on the results of reproducibility and linearity evaluation is highly applicable as a QA dosimeter in the field of therapeutic radiation. The CsPbBr3 dosimeter manufactured in this study presented more than the standard performance in the evaluation of reproducibility and linearity, and it can be used as a radiotherapy QA dosimeter through improvement. 방사선치료에서는 정상조직에 대한 피해를 최소화하면서도 종양조직을 죽이기 위하여 정확한 정도관리 품질보증이 요구된다. 이를 위해서 치료 방사선을 정확하게 계측할 수 있는 선량계가 요구된다. 본 연구에서는 기존 사용되는 검출기 재료로 사용되는 물질보다 저렴하고 제조 공정이 간단하여 기존 물질들을 대체할 수 있는 페로브스카이트 물질에 제조단가를 낮출 수 있고 공정을 간소화 시킬 수 있는 particle in binder(PIB) 방법을 적용하여 민감도가 높은 고효율의 방사선 선량계를 개발하고자 하였다. 고에너지 광자선에 대한 반응특성을 평가함으로써 방사선치료분야에 정도관리 품질보증선량계로 적용 가능한지 적용가능성을 평가하였다. 재현성 평가 결과, 6 MV 에너지에서의 RSD 1.178%로 제시되었고 15 MV에너지에서는 1.141%로 제시되었다. 선형회귀분석에 따른 선형성 평가결과, 6 MV, 15 MV 에너지 각 조건에서 0.9999의 R2값을 제시하였다. 재현성, 선형성 평가결과를 바탕으로 제작된 CsPbBr3 선량계의 치료방사선 분야에 정도관리 품질보증 선량계로의 적용가능성이 높은 것으로 나타났다. 본 연구에서 제작된 CsPbBr3 선량계는 재현성, 선형성 평가에서 기준이상의 성능을 제시하였으며, 개선을 통하여 치료방사선 정도관리 품질보증 선량계로 활용 가능한 것으로 판단된다.

근접방사선치료용 CsPbBr3 선량계 제작 및 적용가능성 평가

양승우,박성광 한국방사선학회 2022 한국방사선학회 논문지 Vol.16 No.4

In brachytherapy, a radiation source is inserted into the body to kill tumor tissue. Therefore, it is important to accurately measure the location of the source and the dose distribution. In this study, a dosimeter that can be used for brachytherapy was developed using CsPbBr3 which is cheaper than the existing detector materials and has a simpler manufacturing process. The CsPbBr3 dosimeter performance was evaluated by analyzing reproducibility, linearity, and distance dependence in 192Ir source. As a result of reproducibility evaluation, the RSD was 1.36%, which satisfies the standard value of 1.5%. As a result of the linearity evaluation, the R2 value was 0.9993, which satisfies the standard R2 of 0.9990. The distance dependence evaluation showed a signal value that decreased exponentially as the distance increased. The evaluation results show that the CsPbBr3 dosimeter satisfies the evaluation criteria and can be used as a brachytherapy quality assurance dosimeter. 근접방사선치료에서는 종양조직을 사멸시키기 위하여 선원을 인체 내부에 삽입하기 때문에 선원의 위치 정확성을 정확히 파악하는 것이 중요하다. 본 연구에서는 기존 사용되는 검출기 재료로 사용되는 물질보다 저렴하고 제조 공정이 간단하여 기존 물질들을 대체할 수 있는 CsPbBr3를 사용하여 근접방사선치료용으로 사용가능한 선량계를 개발하고자 하였다. 그리고 192Ir 선원에서의 재현성, 선형성, 거리의존성 분석하여 선량계의 기초 성능을 평가하였다. 재현성 평가 결과, RSD는 1.36%로 기준치 1.5%를 만족하였다. 선형회귀분석에 따른 선형성 평가결과, 0.9993의 R2값으로 기준치 0.9990 이상의 R2이 제시되었다. 거리의존성 평가결과 거리가 멀어짐에 따라 지수적으로 일정하게 감소하는 신호값을 확인하였다. 재현성, 선형성, 거리의존성 평가결과에 기준 이상의 성능을 제시하여 제작된 CsPbBr3 선량계가 근접방사선치료용 선량계로 활용 가능한 것으로 보여주었다.

Silver thiocyanate treatment-induced enhancement of photoluminescence efficiency of CsPbBr3 perovskite quantum dots

Kim Ho-Young,Cho Seung-Beom,Hou Bo,Park Il-Kyu 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.2

Metal halide perovskite nanostructures have received much attention for many optoelectronic devices, such as solar cells, light-emitting diodes, photodetectors, and sensors due to their sharp emission spectra and adjustable wide optical bandgap. However, low emission efciency and stability still impede their development and application. This paper reports a facile surface modifcation of the CsPbBr3 quantum dots (QDs) to enhance the optical performance using a silver thiocyanate (AgSCN) additive. Structural and chemical investigations show that the QD morphology and size do not change signifcantly, while the SCN– anion is incorporated into the CsPbBr3 QDs as a function of AgSCN loading. In addition, the SCN– anion interacts with Pb2+ in the CsPbBr3 QDs, which indicates that the SCN– anion flls out the Br– anion vacancy site or substitutes the Br- anion without signifcantly afecting the ligand confguration. Therefore, the photoluminescence (PL) intensity and stability of the AgSCN-treated CsPbBr3 QDs are improved compared to the pristine one, because the AgSCN plays a critical role in recovering the appropriate surface stoichiometry and eliminating the defective surface states.

Efficient and stable green-emitting CsPbBr₃ perovskite nanocrystals in a microcapsule for light emitting diodes

Song, Young Hyun,Park, Sang-Yul,Yoo, Jin Sun,Park, Won Kyu,Kim, Hyo Sun,Choi, Seung Hee,Kwon, Seok Bin,Kang, Bong Kyun,Kim, Jae Pil,Jung, Hyun Suk,Yoon, Dae Ho,Yang, Woo Seok,Seo, Young-Soo Elsevier 2018 Chemical Engineering Journal Vol.352 No.-

<P><B>Abstract</B></P> <P>Fully inorganic lead halide perovskite materials have attracted tremendous attention because of their practical applications in optoelectronic devices, such as light emitting diodes. In this work, we report the first development of highly efficient, stable and green-emitting CsPbBr<SUB>3</SUB> perovskite NCs with a PE microcapsule. The CsPbBr<SUB>3</SUB> perovskite NCs were perfectly incorporated inside the PE microcapsule with a multi-lamellar structure, which shows better luminescence characteristics such as a high PLQY and thermal stability Furthermore, our results revealed the high luminous performance with a white conversion efficacy of 62.4 lm W<SUP>−1</SUP>, EQE of 31.8%, CRI of 37.01, and CCT of 6028 K on blue emitting InGaN LED chip. We suggest that our material will be one of the next generation candidate luminescence materials for application in optoelectronic devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We successfully synthesized the efficient and stable green-emitting CsPbBr<SUB>3</SUB> perovskite nanocrystals. </LI> <LI> CsPbBr<SUB>3</SUB> perovskite of using the multi-lamellar microcapsule enhances the PLQY to 40%. </LI> <LI> The encapsulated perovskite NC composite material represents a next generation candidate luminescence material. </LI> </UL> </P>

Effect of embedded chalcogenide quantum dots in PbBr2 film on CsPbBr3 inorganic perovskite solar cells

Eui Jin Lee,Dae-Hwan Kim,Dae-Kue Hwang 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.90 No.-

Inorganic perovskite solar cells (PSCs) are considered prospective alternatives to organic PSCs due to theirefficiency and relative stability. Cesium lead bromide (CsPbBr3) has a complete perovskite structure, isphase stable, exhibits a wide bandgap energy of 2.3 eV under operating conditions, and is regarded as asuitable material not only for stable PSCs, but also for semi-transparent PSCs. In this study, we synthesizeCu–Zn–In–S–Se (CZISSe) quantum dots (QDs) and demonstrate their novel use for improving theperformance of PSC devices. QDs are embedded through ligand-exchange, which replaces long organicchains with thiosulfate (–S2O3) ligands and disperses the S2O3-capped QDs in the PbBr2 solution toprepare QD-blended precursor inks. The QDs promote the crystallization of CsPbBr3 and hole extractionfrom the photoactive layer. As a result, the optimized power conversion efficiency (PCE) of the QDincorporatedPSC is 5.37%, which is a 22.6% enhancement compared to those of the control devices. Thiswork provides an effective and simple process for enhancing the performance of CsPbBr3-based PSCs.

Electron Magnetic Resonance Study of Mn-doped Quantum Dot CsPbBr3 Inside a Phosphate Glass Matrix

염태호,염효영,Pabitra Aryal 한국물리학회 2021 새물리 Vol.71 No.10

Mn2+ ion-doped perovskite CsPbBr3 quantum dots embedded in glass were synthesized by using the melt-quenching technique. An X- band electron magnetic resonance (EMR) spectrometry, showed two sets of Mn2+ EMR spectra in the CsPbBr3 quantum dots at room temperature: One originating from isolated Mn2+ ions and the other set from Mn2+ clusters. As the Mn concentration was increased, the concentration of isolated Mn2+ ions decreased, whereas the concentration of Mn2+ clusters increased. The spectroscopic splitting parameter (g = 2.011) and the hyperfine constant (A = 9.66 mT) were determined using the effective spin Hamiltonian. The Mn2+ ion resides at Pb2+ instead of Cs+ in CsPbBr3 QDs and/or in the fabricated CsPbBr3 glass. If the Mn2+ ion substitute for Pb2+ in the CsPbBr3 QDs, the local site symmetry of the Mn2+ ion is cubic.