Solid State Dye-sensitized Solar Cells with Improved Conductivity and Recombination Based on Polymer Electrolyte : 고분자 전해질의 향상된 전도도와 재결합 성능을 응용한 고체형 연료감응 태양전지

다국어 초록 (Multilingual Abstract)

In recent years, dye-sensitized solar cell (DSC) has been rapidly developed to reach its efficiency from 7% (by O’Regan and Grätzel in1991) to 14.3 % at 1 sun conditions. It has a trend to take place of one of the important traditional energy conversion systems.
This dissertation comprises 7 chapters, where Chapter 1 is an introduction on renewable energy technologies to solve various problems associated with fossil fuels. The photovoltaic device and valuable market developments are taken into great description. In addition, the DSCs operating principle and tandem DSCs are simply introduced.
In Chapter 2, it is discussed the characteristics of four major components and interfaces such as dye, semiconductor, electrolyte and counter electrode in DSCs. Furthermore the concept of electrochemical impedance spectroscopy (EIS) is explained.
In Chapter 3, poly(3,4-ethylenedioxythiophene) (PEDOT) doped with different imidazolium iodides such as DMII, MPII, and BMII showed the improved performance mostly due to the enhancement of Jsc, when compared with Pt or the pristine PEDOT counter electrode. In particular, the NF PEDOT CE doped with 0.1 M DMII has the maximum efficiency of 9.05 %, higher than the traditional Pt counter electrode. Electrochemical techniques such as Tafel, CV, and EIS were used to analyze and understand the increased performance in addition to the Raman spectroscopy.
In Chapter 4, mesoporous TiO2 surface engineering is a field to be still advanced toward highly efficient DSCs utilizing solid-state polymer electrolytes. Herein, a facile and stepwise co-sensitization method is applied for ruthenium C106 dye and organic D131 dye. After the C106 dyes are adsorbed on the TiO2 surface, D131 dyes are subsequently co-adsorbed onto empty sites of the mesoporous TiO2 surface without desorption of the C106 dyes. And their quantity is controlled by varying the concentration of the D131 dye solution. At the optimal concentration of the D131 dye solution, a remarkable energy conversion efficiency of 8.4 % is attained under 1 sun illumination conditions, as a result of a noticeable rise in photocurrent density (Jsc). According to the photovoltaic characterizations, both the light harvesting and the charge collection efficiencies prepared by the co-sensitization process is greatly superior to those of individual C106 or D131 dyes.
In Chapter 5, the concentration of PVdF-HFP in polymer-gel electrolyte was optimized to be 5 wt%. In addition, various additives such as tBP, LiI, GuNCS were added into the 5 wt% PVdF-HFP based polymer gel electrolyte, and the cell performance was improved to a large extent to the overall energy conversion efficiency of 7.05 % under 1 sun conditions due to the increases in both Voc of 0.7 V and Jsc of 14.00 mA/cm2.
In conclusion, it is realized that the overall energy conversion efficiency is promoted up to 30 % by optimizing material and kinetic properties of each component. Therefore, it needs to emphasize the importance of the understanding of structural and kinetic fundamentals on DSC. In this context, the efficiency of solid state DSCs utilizing solid polymer electrolyte would be expected to be increased to a large extent soon.

Keyword: dye sensitized solar cells, renewable energies, NF PEDOT, imidazolium iodide, co-sensitizers, C106, D131, PVdF-HFP, tBP, LiI, GuNCS.

다국어 초록 (Multilingual Abstract)

List of Figure 1
List of Schemes 6
List of Table 7
Nomenclature 9
Abstract (Korean) 13
Chapter 1. Introduction 15
1.1. Background 15
1.2. Evolution of photovoltaic and market value 18
1.3. Dye sensitized solar cells 19
1.4. References 25
Chapter 2. Characterictics of 4 Major Components and Interfaces 27
2.1. Dyes 27
2.2. Nanostructured Metal Oxide Electrodes 28
2.3. Counter electrode 30
2.4. Electrolyte 30
2.5. Characterization of interface and electron transport 33
2.6. References 39
Chapter 3. Polymer Counter Electrode for DSCs Employing Solid Polymer Electrolyte 42
3.1. Introduction 42
3.2.Results ＆ Discussion 49
3.3. Conclusions 60
3.4. References 61
Chapter 4. Co-sensitization of Ruthenium and Organic Dyes 63
4.1 Introduction 63
4.2 Results & Discussion 67
4.3. Conclusions 73
4.4. References 74
Chapter 5. Additive Effects on PVdF-HFP Polymer Electrolyte 76
5.1. Introduction 76
5.2. Results ＆ Discussion 78
5.3. Conclusions 88
5.4. References 89
Chapter 6. Summary 91
Chapter 7. Future prospects 93
7.1. Results ＆ Discussion 93
7.2. References 98
Abstract (English) 99

목차 (Table of Contents)

• List of Figure
• Fig. 1.1.1. The world main energy estimates (From: processing based on renewable energy scheme to 2040 year, Quote: Energy Renewable European Council (EREC) and Advisory German Council on Global Change (WBGU)).
• Fig 1.1.2 The DSCs of published articles (from 1992-2013) year. Data from: Scopus Database.
• Fig.1.1.3. Different efficiencies of solar cells technology Source from National Renewable Laboratory (NREL), 2011.
• Fig 1.2.1. The price and power output for different PV technologies
• Fig 1.2.2. The three main energy about the relation of generating cost and year (2007-2030). (Reference: based on the book of Photovoltaic Roadmap to 2030.
• Fig 1.3.1. Scheme of DSCs
• Fig 1.3.2. Fabrication of DSCs
• Fig.1.3.1.1. A schematic of idealized tandem DSCs of energy level and electron transfer process
• Fig 2.1.1. Dye binding modes, a, unidentate b, binendate chelating, c, bidentate bridging, d and e, H-bonded, carboxylate unit on film surface
• Fig.2.4.1 Schematic representation of the gel and solid polymer electrolyte
• Fig 2.5.1 Arc of Nyquist represented TiO2 based standard DSCs
• Fig 2.5.2. The transmission line model of DSCs.
• (rct is the charge transfer resistance between in the semiconductor TiO2 film and the iodide/triiodide in the electrolyte, Cµ is the chemical capacitance of the semiconductor anatase ; rt is the transport resistance of the electrons in the semiconductor anatase, Zd is the Warburg is showed the Nernst diffusion of triiodide in the electrolyte, RPt and CPt are the ionic transform resistance of the CE and CE layer capacitance (platinized FTO glass), respectively, RFTO and CFTO are the charge-transfer resistance at the exposed FTO-electrolyte interface and the corresponding layer capacitance, respectively, RTO and CTO are the resistance and the capacitance at the FTO glass and semiconductor anatase interface, respectively, respectively; Rs is the series of the resistance, including the sheet resistance of the FTO glass and the interface resistance in the solar cell. L is the thickness of the semiconductor anatase film.
• Fig 2.5.3 Kinetic processes time in DSCs
• Fig.2.5.4.The electron transport process in the interface between electrolyte and mesoporous TiO2 electrode
• Fig 3.1.2. SEM of the left: bare NF-PEDOT right: 0.1 M DMII doped NF-PEDOT
• Fig 3.2.1.1 J-V about the different imidazolium iodide doped NF PEDOT
• Fig 3.2.1.2 IPCE of different imidazolium iodide doped NF PEDOT
• Fig 3.2.2.1. Resistance of imidazolium iodide doped NF PEDOT
• Fig 3.2.2.2. Tafel of different imidazolium iodide doped NF PEDOT
• Fig 3.2.3.1 cyclic volammograms of Pt, NF PEDOT and imidazolium iodide doped NF PEDOT of CE and electrolyte supporting consisting of 10mM LiI, 1mM I2, 0.1M LiClO4, ACN solution on the scan speed is 50 mV/s.
• Fig 3.2.4.1 Raman spectra of pristine NF PEDOT and imidazolium iodide doped NF PEDOT
• Fig 3.2.4.2. The amplification of Raman spectra of pristine NF PEDOT and imidazolium iodide doped NF PEDOT
• Fig 3.2.5.1. The current density and efficiency of different concentration DMII doped NF PEDOT
• Fig 3.2.6.1. The Tafel polarization curve of different concentration DMII doped NF PEDOT
• Fig 3.2.6.2. Resistance of different concentration DMII doped NF PEDOT
• Fig 4.2.1. (a) UV-Vis absorbance spectra of photoanodes sensitized by C106 (A1) or D131 (B1) dye, or by both dyes. A1, 0.5 mM C106 dye; B1, 0.5 mM D131 dye; B2, 0.25 mM D131 dye; B3, 0.125 mM D131 dye. (b) Dye load amounts as calculated from the UV-Vis spectra of (a).
• Fig 4.2.2. Photovoltaic J-V curves of solid polymer electrolyte DSCs with cosensitized photoanodes evaluated under 1 sun illumination conditions.
• Fig 4.2.3. Representative IPCE spectra of solid polymer electrolyte DSCs with cosensitized photoanodes.
• Fig 4.2.4. Representative electron life times of solid polymer electrolyte DSCs with cosensitized photoanodes, as measured by intensity-modulated photovoltage spectroscopy (IMVS) method.
• Fig. 5.2.1.1. The J-V curve of different wt% of PVDF-HFP effect on the photovoltaic performance of the DSCs
• IL：MPII=0.6 M, I2=0.1 M and ACN: MPN= 1:1 (V:V). TiO2 film: 11µm thickness with TiCl4 treating and measure with mask and surface area=0.25cm2.
• Fig 5.2.2.1.The J-V characteristic curves of tBP effects on PVdF- HFP polymer electrolyte.
• Ref: MPII=0.6M, I2=0.1M, 5 wt% PVdF- HFP and ACN: MPN= 1:1 (V:V).
• TiO2 film: 11µm thickness with TiCl4 treating and measure with mask and surface area=0.25cm2.
• Fig 2.5.2.2. The resistance of tBP effect on PVdF-HFP polymer electrolyte
• Fig. 5.2.3.1. The J-V characteristic curves of LiI effects on PVdF-HFP polymer electrolyte
• Ref: MPII=0.6 M, I2=0.1 M, 0.5 M tBP, 5 wt% PVdF- HFP and ACN: MPN= 1:1 (V:V).
• TiO2 film: 11µm thickness with TiCl4 treating and measure with mask and surface area=0.25cm2.
• Fig 5.2.3.2. The resistance of the LiI effect on PVdF-HFP polymer electrolyte
• Fig 5.2.4.1. The J-V characteristic curves of GuSCN effects on PVdF-HFP polymer electrolyte
• Ref: MPII=0.6 M, I2=0.1 M, 0.5 M tBP, 5 wt% PVdF- HFP and ACN: MPN = 1:1 (V:V)
• TiO2 film: 11µm thickness withTiCl4 treating and measure with mask and surface area=0.25cm2
• Fig 5.2.5.1. The J-V curves of optimal different additive effect on PVdF-HFP polymer electrolyte.
• P1: 0.6 M MPII, 0.1 M I2, 5 wt % PVdF- HFP and ACN: MPN= 1:1 (V:V).
• A1: 0.6 M MPII, 0.5 M tBP, 0.1 M LiI, 0.1 M GuNCS, 0.1 M I2, 5 wt % PVdF- HFP and ACN: MPN= 1:1 (V:V).
• TiO2 film: 11µm TiO2 with 0.4 M TiCl4 treating and measured with mask and surface area=0.25cm2.
• Fig 7.1.1 The J-V curves of different dipping temperature of the co-sensitizers (C106 and D131).
• Fig 7.1.3 The J-V curves of the single dye Z907, D205 and co-sensitizers (Z907 and D205).
• Fig 7.1.4. The IPCE of the single dye Z907, D205 and co-sensitizers (Z907 and D205).
• List of Table
• Tab. 2.5.1 Characteristic parameters by impedance measurement
• Tab. 3.2.1.1 J-V different imidazolium iodide doped NF PEDOT
• Tab. 3.2.2.1 Resistance of imidazolium iodide doped NF PEDOT
• Tab. 3.2.6.1. Resistance of different concentration DMII doped NF PEDOT
• Tab. 4.2.1. Photovoltaic characteristic parameters of solid polymer electrolyte DSCs with cosensitized photoanodes evaluated under 1 sun illumination conditions.
• Tab. 5.2.1.1. The performance parameters of different wt% of PVDF-HFP effect on the photovoltaic performance of the DSCs
• Tab 5.2.2.1. The performance parameters of tBP effects on PVdF- HFP polymer electrolyte
• Tab. 5.2.3.1. The Performance parameters of the LiI effect on PVdF-HFP polymer electrolyte
• Tab 5.2.4.1. The performance parameters of the LiI effect on PVdF-HFP polymer electrolyte
• Tab 5.2.5.1. The performance parameters of optimal different additive effect on PVdF-HFP polymer electrolyte
• Tab 7.1.1. The parameters result of different dipping temperature of the co-sensitizers (C106 and D131)
• Tab 7.1.2. The cell parameters of the single dye Z907, D205 and co-sensitizers (Z907 and D205)
• Tab 7.1.3. The cell parameters of high temperature adsorption of the co-sensitizers (Z907 and D205)