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Design and Performance of Electrospun sp2-Carbon Based Active Layer and Flexible Gas Barrier Film in Photovoltaic Devices : 전기 방사된 sp2-탄소 기반 활성층과 유연성 기체 차단성 필름으로 구성된 태양전지 설계 및 성능 평가

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dc.contributor.advisor박종래-
dc.contributor.author김태훈-
dc.date.accessioned2017-07-13T05:40:17Z-
dc.date.available2017-07-13T05:40:17Z-
dc.date.issued2014-02-
dc.identifier.other000000018099-
dc.identifier.urihttps://hdl.handle.net/10371/117937-
dc.description학위논문 (박사)-- 서울대학교 대학원 : 재료공학부, 2014. 2. 박종래.-
dc.description.abstractThis thesis described the design and performance of next generation flexible photovoltaic devices based on sp2-carbon materials for high power conversion efficiency and stability. Photovoltaic devices are capable of converting solar energy into electrical energy, and act as future-oriented energy harvesting devices. Organic photovoltaic devices based on sp2-carbon materials including nanocarbon and conjugated polymers are preferred over conventional photovoltaic devices due to their solution-processable nature, low cost, and flexibility. However, the organic photovoltaic devices are accompanied by issues in efficiency and lifetime. Therefore, it is highly important to develop organic photovoltaic devices with enhanced power conversion efficiency and long stability. The aim of this study is to identify the factors that can be varied in order to achieve these requirements by examining the theoretical considerations, and then to design the photovoltaic devices for high efficiency and long lifetime.
Part I provides a general introduction regarding sp2-carbon materials and organic photovoltaic devices. Using theoretical considerations and state of the art analysis, the factors for photovoltaic devices with high efficient and long lifetime are extracted. The aims of the present work are introduced on the basis of these derived factors.
In Part II, with the aim of enhancing power conversion efficiency, organic photovoltaic cell based on one-dimensional conjugated polymers is prepared. Electrospinning techniques are used to prepare conjugated polymer nanofibers and photovoltaic devices in ambient air, regardless of relative humidity condition. The diameters of the conjugated polymer nanofibers are approximately twice the exciton diffusion length, 20nm. The short circuit current and power conversion efficiency of the device increased to 11.54 mA/cm2 and 5.82 %, respectively. The suggested method can be applied to the fabrication, in ambient air, of large-area active layers composed of other new conjugated polymers to yield high-performance OPV devices.
Part III discusses the preparation and properties of reduced graphene oxide-based gas barrier films for the enhancement of the stability of organic photovoltaic devices. The simple and direct spin-casting of a graphene oxide suspension on an aluminum electrode is performed to encapsulate the OPV device with reduced graphene oxide film. The lifetime of the OPV device after the reduction process was increased by 100 times compared to an unencapsulated OPV device. Furthermore, the gas barrier property is enhanced more by controlling the thermal reduction condition. The gas barrier property is closely related to the surface roughness, dispersibility and reduction condition of graphene oxide. Flexible photovoltaic devices encapsulated by the reduced graphene oxide-based gas barrier film are prepared. The reduced graphene oxide allows a long lifespan while maintaining flexibility. Further investigations of the preparation and reduction of the graphene oxide film would improve the performance.		-
dc.description.tableofcontentsContents

Part I Basic research for organic photovoltaic devices

Chapter 1. Introduction 2
1.1 General introduction to photovoltaic devices 2
1.1.1 Overview of photovoltaic devices 2
1.1.2 Demand for generation photovoltaic devices 5
1.1.3 Next-generation photovoltaic devices: sp2-carbon-based organic photovoltaic devices 6
1.2 Theoretical consideration for the sp2-carbon-based photovoltaic devices 9
1.2.1 Review of carbon-based electronic materials 9
1.2.1.1 Carbon nanomaterials 9
1.2.1.2 Conjugated polymers 17
1.2.2 Structure of the organic photovoltaic devices 20
1.2.2.1 Transparent electrode 22
1.2.2.2 Hole transport layer 24
1.2.2.3 Active layer 24
1.2.2.3.1 Formation of excitons in a polymer 24
1.2.2.3.2 Heterojunction structure 26
1.2.2.3.3 Limited exciton diffusion length in a polymer 26
1.2.2.3.4 Bulk heterojunction structure 27
1.2.2.4 Cathode 27
1.2.2.5 Encapsulation layer 28
1.3 State-of-the-art works on organic photovoltaic devices 28
1.3.1 High-performance devices 28
1.3.1.1 Synthesis of a new conjugated polymer 29
1.3.1.2 Synthesis of a new acceptor 29
1.3.1.3 Control of the morphology 30
1.3.1.3.1 Conventional method to control the morphology of the active layer 30
1.3.1.3.2 Rational morphology control by 1D conjugated polymers 34
1.3.2 Long-lifetime devices 42
1.3.2.1 Encapsulation design 42
1.3.2.2 Inverted solar cell 42
1.4 Aim and scope of this research 45
1.4.1 Efficiency enhancement of photovoltaic devices 45
1.4.1.1 Issue: Limited materials that form self-assembled nanowire 45
1.4.1.2 Preparation and characterization of P3HT nanofibers 46
1.4.1.3 Preparation of highly reproducible photovoltaic devices based on P3HT nanofibers 46
1.4.1.4 Performance of photovoltaic devices based on PCDTBT nanofibers 46
1.4.2 Preparation of flexible and long-lifetime photovoltaic devices 47
1.4.2.1 Issue: incompatibility of conventional encapsulation methods and flexibility 47
1.4.2.2 Preparation and characterization of flexible gas barrier film 47
1.5 References 49
 
Part II Design and Performance of a Nanoweb of a Conjugated Polymer-Nanofiber-Based Active Layer for High-Performance Photovoltaic Devices

Chapter 2. Preparation and Characterization of Electrospun Conjugated Polymer Nanofibers 54
2.1. Introduction 54
2.2. Experimental section 58
2.2.1. Chemicals and materials 58
2.2.2. Electrospinning 58
2.2.3. Characterization 59
2.2.4. PL test 59
2.3. Results and discussion 61
2.3.1. Control of the diameters of the P3HT nanofibers 61
2.3.2 Optical properties of the nanofibers 82
2.3.3. Photoluminescence quenching 86
2.4. Conclusions 89
2.5. References 90
Chapter 3. Highly Reproducible Electrospun Conjugated Polymer Nanofibers Based Photovoltaic Devices 93
3.1. Introduction 93
3.2. Experimental Section 98
3.2.1. Chemicals and materials 98
3.2.2. Electrospinning 98
3.2.3. Fabrication of the OPV devices 99
3.2.4. Characterization 99
3.3 Results and discussion 100
3.4. Conclusions 123
3.5. References 124

Chapter 4. Preparation and Performance of PCDTBT Nanofibrous Photovoltaic Devices 126
4.1. Introduction 126
4.2. Experimental Section 128
4.2.1. Chemicals and materials 128
4.2.2. Fabrication and characterization of the nanofibers 128
4.2.3. Fabrication and characterization of the OPV devices 129
4.3. Result and Discussions 131
Figure 4.1. Schematic diagram showing the preparation of a nanofibrous OPV device. 132
Figure 4.3. The viscosities of the spinning dope solutions. 137
4.4 Conclusions 168
4.5. References 169
 
Part III Design and Performance of a Carbon-Nanomaterial-Based Encapsulation Layer and Electrodes for Flexible Photovoltaic Devices

Chapter 5. Preparation and Characterization of Reduced Graphene Oxide Based Encapsulation Film 174
5.1. Introduction 174
5.2. Experimental 176
5.2.1. Preparation of the GO solution 176
5.2.2. Fabrication and characterization of OPV devices 176
5.2.3. Preparation and characterization of the rGO film 177
5.2.4. Fabrication of a flexible OPV device 177
5.3. Results and discussion 178
5.3.1. Direct preparation of rGO films on OPV devices for encapsulation 178
5.3.2. Preparation of flexible rGO-based encapsulation films 192
5.4. Conclusion 211
5.5. Reference 212
Chapter 6. Concluding remarks 214		-
dc.formatapplication/pdf-
dc.format.extent13596792 bytes-
dc.format.mediumapplication/pdf-
dc.language.isoko-
dc.publisher서울대학교 대학원-
dc.subjectphotovoltaic-
dc.subjectcarbon nanomaterials-
dc.subjectelectrospinning-
dc.subjectconjugated polymer-
dc.subjectnanofiber-
dc.subjectflexible device-
dc.subject.ddc620-
dc.titleDesign and Performance of Electrospun sp2-Carbon Based Active Layer and Flexible Gas Barrier Film in Photovoltaic Devices-
dc.title.alternative전기 방사된 sp2-탄소 기반 활성층과 유연성 기체 차단성 필름으로 구성된 태양전지 설계 및 성능 평가-
dc.typeThesis-
dc.contributor.AlternativeAuthorTaehoon Kim-
dc.description.degreeDoctor-
dc.citation.pagesxxiv, 218-
dc.contributor.affiliation공과대학 재료공학부-
dc.date.awarded2014-02-
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