Quantum dot-sensitized solar cells based on novel transition-metal-sulfides.

• Other Authors: Cheng, Kai Chun.
• Format: Others
• Language: English; Chinese
• Published: 2012
• Subjects: Solar cells; Quantum dots; Sulfides > Metallurgy
• Online Access: http://library.cuhk.edu.hk/record=b5549177; http://repository.lib.cuhk.edu.hk/en/item/cuhk-328096

本論文示範了兩款過渡金屬硫化物量子點 (二硫化銀銦量子點與硫化錳量子點) 在量子點敏化太陽能電池上作為光敏化劑的應用，這也是它們在量子點敏化太陽能電池上的初次應用。 === 二硫化銀銦量子點的合成採用了一鍋合成法，合成的量子點隨後透過3-巰基丙酸連接到二氧化鈦的表面。研究發現，當量子點溶液的濃度處於較低水平的時候，量子點在二氧化鈦的吸附量會較高。另外，從不同研究小組在量子點吸附行為的報告中，觀察到量子點的吸附行為決定於實驗條件，如量子點的大小和表面活劑，納米二氧化鈦多孔膜的孔隙度和量子點的溶劑。實驗中，最高性能的二硫化銀銦量子點敏化太陽能電池的短路電流為0.49 mA/cm²，開路電壓為0.245 V，填充因子為38.26 %，光電轉換效率為0.046 %。 === 透過連續離子層沉積反應法，硫化錳量子點生長並組裝到二氧化鈦的表面上。能譜測量顯示，錳跟硫的比率在不是1:1。這現象懷疑是源於錳(2+)的小離子半徑，對錳(2+)和硫(2-)之間的化學反應產生了不良的影響，導致吸附了的錳(2+)沒有反應過來。通過優化連續離子層沉積反應法週期的數量，最高性能的硫化錳量子點敏化太陽能電池的短路電流為0.65 mA/cm²，開路電壓為0.30 V，填充因子為48.21 %，光電轉換效率為0.095 %。 === QD-SSCs sensitized with novel transition metal sulfides have been demonstrated. Both AgInS₂ QD-SSC and MnS QD-SSC presented in this thesis are new and are the first demonstrated works in the research field. === AgInS₂ QDs was synthesized by one-pot hot colloidal synthesis approach. The as-synthesized QDs were attached to the TiO₂ surface through 3-mercaptopropionic acid. Optimization process on QDs adsorption was done, and it has been observed that the amount of QDs adsorbed is higher when the concentration of the QDs solution is at low level. The variations in the behaviors in QDs adsorption between works from different research groups are considered to originate from experimental conditions such as the sizes and surfactants of QDs, porosities in the TiO₂ matrix, and the solvent for QDs dispersion. The optimized AgInS₂ QD-SSC attained a short-circuit current of 0.49 mA/cm², an open-circuit voltage of 0.245 V, a fill factor of 38.26 % and a power conversion efficiency of 0.046 %. IPCE measurements confirm the successful sensitization from AgInS₂ QDs, indicating the energetically favourable electron injection from AgInS₂ QDs to TiO₂. === By adopting the SILAR technique, MnS QDs was in-situ grown and deposited on the TiO₂ surface. EDX measurements indicated that the Mn/S ratio in the TiO₂/MnS film is not 1:1. The reason is suspected to originate from the small ionic radius of Mn²⁺ that promoted an adverse effect on the reaction between Mn²⁺ and S²₋. It is proposed that a portion of the adsorbed Mn²⁺ did not react with the S²₋., resulting an excess concentration of Mn²⁺ in the film. By optimizing the number of SILAR cycles, MnS QD-SSC was optimized to exhibit a short-circuit current of 0.65 mA/cm², an open-circuit volatge of 0.30 V, a fill factor of 48.21 % and a power conversion efficiency of 0.095 %. IPCE measurements confirm the sensitization is originated from MnS QDs, which consequently reveal an energetically favourable electron injection from the MnS QDs to TiO₂. === Detailed summary in vernacular field only. === Detailed summary in vernacular field only. === Detailed summary in vernacular field only. === Cheng, Kai Chun. === Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. === Includes bibliographical references. === Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. === Abstracts also in Chinese. === Chapter Chapter 1 --- Introduction --- p.1 === Chapter 1.1 --- Background --- p.1 === Chapter 1.2 --- Solar cells --- p.2 === Chapter 1.2.1 --- Developments --- p.2 === Chapter 1.2.2 --- Nanostructured solar cells --- p.4 === Chapter 1.2.2.1 --- Bilayer organic solar cells --- p.4 === Chapter 1.2.2.2 --- Bulk heterojunction organic solar cells --- p.5 === Chapter 1.2.2.3 --- Organic-inorganic hybrid solar cells --- p.7 === Chapter 1.2.2.4 --- Dye-sensitized solar cells --- p.8 === Chapter 1.2.2.5 --- Quantum dot-sensitized solar cells --- p.11 === Chapter 1.2.3 --- Characterization of solar cells --- p.11 === References --- p.14 === Chapter Chapter 2 --- Quantum dot-sensitized solar cells --- p.18 === Chapter 2.1 --- Quantum dots --- p.18 === Chapter 2.1.1 --- Quantum confinement --- p.18 === Chapter 2.1.2 --- Multiple exciton generation --- p.20 === Chapter 2.2 --- Quantum dot-sensitized solar cell --- p.22 === Chapter 2.2.1 --- Principles --- p.22 === Chapter 2.2.2 --- Assembly of oxide/quantum dot film --- p.25 === Chapter 2.2.3 --- Light harvesting and electron injection --- p.29 === Chapter 2.2.4 --- Titanium dioxide as electron acceptor --- p.33 === Chapter 2.2.5 --- Redox process of electrolyte --- p.37 === Chapter 2.2.6 --- Counter electrode materials --- p.39 === References --- p.41 === Chapter Chapter 3 --- Experimental Details --- p.45 === Chapter 3.1 --- Materials --- p.45 === Chapter 3.2 --- Preparation of the TiO₂ mesoporous film --- p.46 === Chapter 3.3 --- Synthesis of AgInS₂ quantum dots --- p.47 === Chapter 3.4 --- Preparation of the TiO₂/QDs film --- p.47 === Chapter 3.5 --- Configuration of the QD-sensitized solar cell --- p.49 === Chapter 3.6 --- Characterization and Photoelectrochemical Measurements --- p.51 === References --- p.52 === Chapter Chapter 4 --- Experimental Results --- p.53 === Chapter 4.1 --- AgInS₂ QD-sensitized solar cell --- p.54 === Chapter 4.1.1 --- Characterization of AgInS₂ QDs --- p.54 === Chapter 4.1.2 --- Adsorption of AgInS₂ QDs on the TiO₂ surface --- p.56 === Chapter 4.1.3 --- Photoelectrochemical measurements of the AgInS₂ QD-SSC --- p.60 === Chapter 4.2 --- MnS QD-sensitized solar cell --- p.64 === Chapter 4.2.1 --- Characterization of MnS QDs --- p.64 === Chapter 4.2.2 --- Photoelectrochemical measurements of the MnS QD-SSC --- p.69 === References --- p.74 === Chapter Chapter 5 --- Discussions and Conclusions --- p.75 === Chapter 5.1 --- Discussions --- p.76 === Chapter 5.1.1 --- AgInS₂ QD-SSC --- p.76 === Chapter 5.1.1.1 --- Adsorption of AgInS₂ QDs on the TiO₂ surface --- p.76 === Chapter 5.1.1.2 --- Electron injection --- p.80 === Chapter 5.1.1.3 --- Problems encountered and future directions --- p.83 === Chapter 5.1.2 --- MnS QD-SSC --- p.84 === Chapter 5.1.2.1 --- Growth of MnS QDs on the TiO₂ surface --- p.85 === Chapter 5.1.2.2 --- Effects of SILAR cycles on MnS QD-SSC --- p.86 === Chapter 5.1.2.3 --- Problems encountered and future directions --- p.88 === Chapter 5.1.3 --- AgInS₂ QD-SSC versus MnS QD-SSC --- p.89 === Chapter 5.2 --- Conclusions --- p.91 === References --- p.94