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n-Doping of Electron Transporting Layer for High Performance Perovskite Solar Cells with Planar Heterojunction Architecture : 평면 이종접합 구조를 갖는 고성능의 페로브스카이트 태양전지를 위한 전자 수송층의 n-도핑

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dc.contributor.advisor조원호-
dc.contributor.author김신성-
dc.date.accessioned2017-07-13T05:49:17Z-
dc.date.available2017-07-13T05:49:17Z-
dc.date.issued2016-02-
dc.identifier.other000000132282-
dc.identifier.urihttps://hdl.handle.net/10371/118046-
dc.description학위논문 (박사)-- 서울대학교 대학원 : 재료공학부, 2016. 2. 조원호.-
dc.description.abstractOrganic-inorganic hybrid perovskite has intensively been studied as light absorber for efficient photovoltaic cells because of its unique and superior intrinsic properties such as long charge carrier diffusion length, excellent charge carrier transport, low exciton binding energy, and high absorption coefficient. Furthermore, thin films of organic-inorganic perovskites can be easily fabricated from abundant and inexpensive precursor materials. In spite of their short history, the photovoltaic performances of perovskite solar cells have advanced dramatically with surpassing a power conversion efficiency (PCE) of 20%.
Particularly, inverted structure of planar heterojunction perovskite solar cell with a device configuration of ITO/PEDOT:PSS/perovskite(CH3NH3PbI3) /electron transporting material/Al has attracted much attention due to an advantage of low-temperature and solution processibility over the normal structure. For inverted perovskite solar cells, fullerene derivatives such as C60, PCBM, PC71BM, and ICBA have commonly been used as electron transporting layer (ETL) material because of their room temperature solubility and orthogonal solvent processibility on the perovskite layer.
In organic photovoltaics, non-fullerene electron acceptors based on polymers and small molecules have recently been developed because of their unique advantages over fullerene derivatives such as high absorption in visible range, tunable energy level, and low production cost. However, since inverted perovskite solar cells require sufficiently thick ETL to prevent direct contact between perovskite layer and metal cathode, the non-fullerene acceptors as ETL material of perovskite solar cells must have sufficiently high electrical conductivity and high electron mobility.
1,3-Dimethyl-2-phenyl-2,3-dihydro-1H-benzoimidazole (DMBI) has been reported as an effective n-type dopant for enhancing the electrical properties of n-type materials such as fullerene or naphthalene diimide derivatives. Since DMBI has good solubility in common organic solvents, the doping is easily achieved by simply mixing with n-type material in organic solvents. DMBI is expected to effectively dope the electron transporting materials and thus to enhance the solar cell performance of planar heterojunction perovskite solar cells.
In this study, a simple n-doping method to enhance the performance of n-type materials as electron transporting layer of perovskite solar cells with planar heterojunction architecture is investigated. n-Type materials used in this study are PCBM and perylene diimide-based small molecules. When a small amount of DMBI is added to ETL materials, it reveals that DMBI effectively dopes the ETL as clearly evidenced by up-shift of the Fermi level. Further, the device with DMBI-doped ETL exhibits high PCE with remarkably enhanced short-circuit current density as compared to the device with undoped ETL, mainly due to the greatly increased electrical conductivity of ETL materials. When the charge transfer characteristics are identified by photoluminescence measurements, it reveals that the electron accepting ability of diPDI is comparable to that of PCBM.
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dc.description.tableofcontentsChapter 1 Introduction 1
1.1 Organic-inorganic hybrid perovskite solar cells 1
1.1.1 Organic-inorganic hybrid perovskites 1
1.1.2 Advantages of organic-inorganic hybrid perovskites as solar cell materials 5
1.1.2.1 Charge carrier diffusion lengths 6
1.1.2.2 Charge carrier mobility 8
1.1.2.3 Exciton binding energy 8
1.1.2.4 Optical properties 10
1.1.3 Classification by device structure 13
1.1.4 Fabrication methods for organic-inorganic hybrid perovskite films 16
1.2 Planar heterojunction perovskite solar cells with inverted device configuration 19
1.2.1 Operating principles 19
1.2.2 Device structure 22
1.2.3 n-Doping method 26
1.2.4 Non-fullerene electron acceptors 29
1.3 Objectives of this study 33

Chapter 2 Experimental Section 36
2.1 Synthesis and characterization 36
2.1.1 Materials 36
2.1.2 Synthesis of organic precursor of perovskite films 37
2.1.3 Fabrication of perovskite films 38
2.1.4 Synthesis of titanium dioxide nanoparticles 39
2.1.5 Synthesis of n-type dopant 39
2.1.6 Synthesis of non-fullerene acceptors 41
2.1.6.1 Synthesis of N,N-bis(1-propylbutyl)perylene-3,4:9,10-tetracarboxylic diimide 41
2.1.6.2 Synthesis of 1-bromo-N,N-bis(1-propylbutyl)perylene-3,4:9,10-tetracarboxylic diimide 41
2.1.6.3 Synthesis of diPDI 42
2.1.7 Characterization methods 42
2.2 Device fabrication and measurements 44
2.2.1 Materials 44
2.2.2 Fabrication of solar cell devices 45
2.2.2.1 Fabrication of solar cell devices with PCBM ETL 45
2.2.2.2 Fabrication of solar cell device with non-fullerene ETL 46
2.2.3 Solar cell performance measurements 46

Chapter 3 Results and Discussion 48
3.1 Performance enhancement of inverted structure planar heterojunction perovskite solar cells by n-doping of PCBM electron transporting layer 48
3.1.1 Synthesis and characterization 48
3.1.2 Characterization of n-doping 50
3.1.3 Photovoltaic properties 54
3.1.4 Effects of excessive doping on photovoltaic properties 60
3.1.5 Summary 65
3.2 Perylene diimide-based non-fullerene acceptors as electron transporting materials for inverted structure planar heterojunction perovskite solar cells and the performance enhancement by n-doping 67
3.2.1 Synthesis and characterization 67
3.2.2 Charge transfer characteristics 69
3.2.3 Photovoltaic properties 72
3.2.4 Characterization of n-doping 76
3.2.5 Effects of excessive doping on photovoltaic properties 79
3.2.6 PDI monomer as ETL material 82
3.2.7 Summary 86

Chapter 4 Conclusions 89

Bibliography 93

Korean Abstract 103
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dc.formatapplication/pdf-
dc.format.extent4129364 bytes-
dc.format.mediumapplication/pdf-
dc.language.isoen-
dc.publisher서울대학교 대학원-
dc.subjectperovskite solar cells-
dc.subjectelectron transporting layer-
dc.subject.ddc620-
dc.titlen-Doping of Electron Transporting Layer for High Performance Perovskite Solar Cells with Planar Heterojunction Architecture-
dc.title.alternative평면 이종접합 구조를 갖는 고성능의 페로브스카이트 태양전지를 위한 전자 수송층의 n-도핑-
dc.typeThesis-
dc.contributor.AlternativeAuthorShin Sung Kim-
dc.description.degreeDoctor-
dc.citation.pagesxii, 105-
dc.contributor.affiliation공과대학 재료공학부-
dc.date.awarded2016-02-
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