View : 1386 Download: 0

Full metadata record

DC Field Value Language
dc.contributor.advisor김동하-
dc.contributor.authorQuan Lina-
dc.creatorQuan Lina-
dc.date.accessioned2016-08-26T04:08:28Z-
dc.date.available2016-08-26T04:08:28Z-
dc.date.issued2016-
dc.identifier.otherOAK-000000126914-
dc.identifier.urihttps://dspace.ewha.ac.kr/handle/2015.oak/215023-
dc.identifier.urihttp://dcollection.ewha.ac.kr/jsp/common/DcLoOrgPer.jsp?sItemId=000000126914-
dc.description.abstract페로브스카이트는 CaTiO3 와 같은 결정 구조를 갖고 있는 AMX3 화합물을 통칭하는데 러시아 과학자인 페로브스키를 기념하여 페로브스카이트 화합물이라고 부른다. 여기서 A, M은 금속 양이온이고 X는 할로겐화물 또는 산화물을 포함하는 음인온이다. AMX3 구조는 정육면체 단위격자의 꼭짓점에 크기가 큰 양이온 A가 있고 가운데 크기가 A에 비하여 상대적으로 작은 양이온 M이, 각 면에 중앙에 음이온 X가 존재하는 구조이다. 페로브스카이트는 A 와 M, X 에 어떤 원자가 있느냐에 따라 수백 가지 종류가 알려져 있다. 그중에도 유기물-무기물 할로겐화합물로 조성된 페로브스카이트가 최근 차세대 반도체로 떠오르게 되였다. 이러한 페로브스카이트의 놀라운 점은 성능이 우수하여 자체적 광전하 축척 및 반도체로의 활용이 가능하여 다양한 형태의 태양전지 구현 및 타 기술과의 템덤화 (하이브리드화)가 용이하다. 다만 페로브스카이트 결정의 단점은 습기에 약하다, 하여 안정성 문제점을 해결하는 것이 시급한 과제이다. 또한 페로브스카이트 소재의 우수한 전자-홀 결합 성능은 차세대 디스플레이에의 응용 가능성을 제시 하였다. 본 연구의 제1장에서는 본 연구의 이해를 돕기 위한 페로브스카이트의 배경 및 일반적 지식을 서술하였으며, 페로브스카이트의 광전 소자 및 발광다이오드 응용 및 소자구조와 작도원리 그리고 최근 연구동향을 소개하였다. 본 연구의 제2장에서는 3D 구조의 페로브스카이트에 PEAI 유기물 리간드를 도입한 차원제어 quasi-2D 페로브스카이트 구조체를 제시하고 태양전지에의 응용을 소개하였다. 차원제어를 통하여 기존 3D 페로브스카이트의 전기적, 광학적인 성질을 확보함과 동시에 안정성 문제점을 해결하고 반면에 높은 광전 변환 효율을 유지하는 결과이다. 본 연구의 제3장에서는 차원제어 페로브스카이트의 근-적외선 발광 다이오드에 응용한 내용을 소개하였다. 기존 3D 페로브스카이트는 상온에서 exciton 결합 에너지가 상대적으로 작은 반면에 차원제어 quasi-2D 페로브스카이트는 비교적 큰 장점이 있고 또한 차원제어 페로브스카이트의 부동한 multi-phase로 인한 에너지 전달 현상을 규명하였다. 이는 고 효율의 발광 다이오드 개발에 아주 중요한 요소임을 증명한 결과를 서술하였다. 본 연구의 제4장에서는 차원제어 페로브스카이트의 가시광선 발광 다이오드에 응용한 내용을 서술하였다. 이론적인 계산을 통하여 차원제어 페로브스카이트의 에너지 전달현상 및 메커니즘을 규명하고 광학적인 분석을 통하여 증명하였고 높은 발광 다이오드 효율을 소개하는 결과이다. 본 연구의 제5장에서는 CsPbX3 기반의 무기물 페로브스카이트 quantum dot 표면 개질 연구와 발광 다이오드에의 응용을 소개하였다. 기존 길이가 긴 oleic acid 유기물 리간드를 짧고 안정한 리간드로 대체를 하면서 페로브스카이트 quantum dot 필름의 안정성을 높임과 동시에 발광 다이오드에서의 효율이 증가 하는 결과를 소개하고 있다. ;CHAPTER I Organic inorganic perovskites (OIPs) have recently been established as an important class of materials, which exhibit excellent magnetic, electrical and optical properties. Especially in three-dimensional (3D) lead (II) halide perovskites, possess great chemical flexibility and outstanding potential of the photovoltaic applications. Perovskite solar cells (PSCs) are rapidly emerging as challengers to competing the leading photovoltaic technologies. Moreover, lower dimensional perovskites family exhibit interesting electronic, optical and energy-based properties, results in various light-emitting application (i.e., light emitting diodes and lasers). CHAPTER Ⅱ Metal halide perovskites have rapidly advanced thin film photovoltaic performance; as a result, the materials’ observed instabilities urgently require a solution. Using density functional theory (DFT), we show that a low energy of formation, exacerbated in the presence of humidity, explains the propensity of perovskites to decompose back into their precursors. We find, also using DFT, that intercalation of phenylethylammonium between perovskite layers introduces quantitatively appreciable van der Waals interactions; and these drive an increased formation energy and should therefore improve material stability. Here we report the reduced-dimensionality (quasi-2D) perovskite films that exhibit improved stability while retaining the high performance of conventional three-dimensional perovskites. Continuous tuning of the dimensionality, as assessed using photophysical studies, is achieved by the choice of stoichiometry in materials synthesis. We achieve the first certified hysteresis-free solar power conversion in a planar perovskite solar cell, obtaining a 15.3% certified PCE, and observe greatly improved performance longevity. CHAPTER Ⅲ Organometal halide perovskites exhibit large bulk crystal domain sizes, rare traps, excellent mobilities, and carriers that are free at room temperature – properties that support their excellent performance in charge-separating devices. In devices that rely on the forward injection of electrons and holes, such as light-emitting diodes (LEDs), excellent mobilities contribute to the efficient capture of nonequilibrium charge carriers to rare nonradiative centres. Moreover, the lack of bound excitons weakens the competition of desired radiative over undesired nonradiative recombination. Here we report a perovskite mixed material, one comprised of a series of differently quantum-size-tuned grains, that funnels photoexcitations to the lowest-bandgap light-emitter in the mixture. The materials function as charge carrier concentrators, ensuring that radiative recombination successfully outcompetes trapping and hence nonradiative recombination. We use the new material to build devices that exhibit an external quantum efficiency (EQE) of 8.8% and a radiance of 80 Wsr-1m-2. These represent the brightest and most efficient solution-processed near-infrared LEDs to date. CHAPTER Ⅳ Organo-metal halide perovskites are a promising platform for light emitting applications in view of their excellent charge transport and bandgap tunability; however, they have to date suffered from low photoluminescence quantum efficiency, especially in the low excitation regime. Consequently, perovskite light emitting devices are operated under high injection, a regime under which the materials have so far been unstable. Here we report a new family of perovskites engineered so that carriers can be concentrated into a small fraction of the volume of the active material, thereby reaching high quantum yield at moderate excitation intensities. The active layer consists of a distribution of perovskite nanoparticles having a range of quantum-confined bandgaps. We show that photocharges are funneled into the lowest-bandgap minority phase more rapidly than when they are trapped to nonradiative centres. This new strategy allows carriers to accumulate, thereby enabling radiative recombination to outcompete trap-assisted losses. The new material exhibits 60% photoluminescence quantum yield at excitation densities as low as 1 mW/cm2, yielding a maximum yield-to-driving-power value of 0.6 cm2/mW: this represents a two-orders of magnitude improvement in the excitation power required to reach high efficiency. Based on this strategy, we report visible light LEDs with EQEs up to 7.4% having high luminescence (8400 cd/m2). CHAPTER V Develop a two-step ligand exchange strategy that allows for replacing the long carbon chain ligands on all-inorganic perovskite (CsPbX3, X=Br, Cl, I) quantum dots with halide ion-pair ligands. Green and blue light-emitting diodes made from the halide ion-pair capped quantum dots exhibit the higher external quantum efficiencies for CsPbX3 QDs compare to the untreated. We demonstrated the flexibility and generality of our ligand exchange strategy by exploiting mixed halide ion pairs to tune the emission of the QDs and further to fabricate blue perovskite LEDs possessing an EQE of 0.18% with a maximum luminance of 35 cd m-2 at a voltage 7.5 V. The reported efficiencies for both green and blue perovskite LEDs in this work represent a major leap for the family of APQD materials and pave the way to further their exploitation in optoelectronics through judicious surface engineering.-
dc.description.tableofcontentsI. Introduction 1 A. Organic-Inorganic Perovskites (OIPs) 2 1. Background of perovskites 2 2. Three-dimensional (3D) organic-inorganic perovskites (OIPs) 3 3. Lower-dimensional layered OIPs 8 4. Zero-dimensional (0D) perovskites 13 B. Photovoltaic Application of OIPs 16 1. Overview of perovskite solar cells (PSCs) 16 2. Device architecture and operation principle of PSCs 21 3. Fabrication of PSCs 26 4. Summary of recent research of PSCs: reduced hysteresis and enhanced stability of the device 30 C. Light Emitting Application of Perovskites 34 1. Overview 34 2. LED application of perovskites 37 3. Laser application of perovskites 41 4. Summary of recent research for perovskite LEDs 44 D. Organization of the Thesis 48 References 49 II. Ligand-Stabilized Reduced Dimensionality Perovskites for photovoltaics 55 A. Introduction 56 B. Experimental Section 58 C. Results and Discussion 62 1. Energetics of perovskite formation and stability 62 2. Details for DFT simulations for the perovskite stability 65 3. Structure and optical characterization of dimensionally-tuned perovskite 68 4. Photophysical and structural stability of 3D and quasi-2D perovskite films 72 5. Photovoltaic application of quasi-2D perovskites and device simulation 75 6. Solar cell architecture and device performance 80 7. Solar cell device stability 87 D. Conclusions 96 References 97 III. Perovskite Energy Funnels for Efficient Near-Infrared Light-Emitting Diodes 100 A. Introduction 101 B. Experimental Section 103 C. Results and Discussion 108 1. Structure and photoluminescence of the quasi-2D perovskites 108 2. Carrier funneling in quasi-2D perovskite solids 118 3. Microscopy study of quasi-2D perovskite solids 127 4. LED device structure and performance 131 D. Conclusions 140 References 141 IV. Engineered Energy Transfer Enables Efficient Visible Light Luminescence in Multidomain Quasi-2DPerovskites 145 A. Introduction 146 B. Experimental Section 148 C. Results and Discussion 152 1. Radiation and energy transfer mechanisms in low-dimensional organo halide perovskite 152 2. Leveraging energy transfer in multidimensional OIPs for light emission 155 3. Stochastic Monte Carlo modelling of recombination kinetics 157 4. Material characterization 159 5. Maximizing PLQY and reducing pump threshold through material configuration 165 6. Subthreshold LED with high EQE 174 D. Conclusions 179 References 180 V. Highly Efficient Perovskite Quantum-Dot Light Emitting Diodes by Surface Engineering 182 A. Introduction 183 B. Experimental Section 185 C. Results and Discussion 188 1. Perovskite QD synthesize and characterization 188 2. Perovskite QD film and LED device architecture 197 3. Performance of perovskite QD LEDs 204 D. Conclusions 208 References 209 Appendix(Curriculum Vitae) 213 Abstract (in Korean) 221-
dc.formatapplication/pdf-
dc.format.extent10463906 bytes-
dc.languageeng-
dc.publisher이화여자대학교 대학원-
dc.subject.ddc500-
dc.titleReduced Dimensionality Perovskites for Photovoltaics and Light Emitting Diodes-
dc.typeDoctoral Thesis-
dc.format.pagexxxi, 222 p.-
dc.description.localremark박170-
dc.contributor.examiner박종혁-
dc.contributor.examiner김동하-
dc.contributor.examiner임상혁-
dc.contributor.examiner현가담-
dc.contributor.examinerEdward. H. Sargent-
dc.identifier.thesisdegreeDoctor-
dc.identifier.major대학원 화학·나노과학과-
dc.date.awarded2016. 8-
Appears in Collections:
일반대학원 > 화학·나노과학과 > Theses_Ph.D
Files in This Item:
There are no files associated with this item.
Export
RIS (EndNote)
XLS (Excel)
XML


qrcode

BROWSE