硫化鉛量子點因具有尺寸可調控之紅外光放光波長而受到廣泛研究，其特殊之光電性質在光電元件應用上有突出之發展潛力，如太陽能電池，發光二極體及螢光太陽能集中器等。本研究藉由改變不同的反應參數，包含調控不同的反應溫度，前驅物莫耳比率及前驅物的反應性，最後可得到放光波長範圍介於950到1600 nm之間的硫化鉛量子點，我們並比較了硫化鉛量子點不同的光學性質與表面化學特性間之關係。此外，我們利用陽離子交換法合成出硫化鉛-硫化鎘核殼量子點結構，經表面化學分析確認，可知因硫化鎘殼層的包覆鈍化了硫化鉛量子點的表面缺陷，使得此核殼量子點的光致放光(PL)相對強度有效提升。最後，在探討提高反應溫度(> 150 °C)以成長厚殼(> 1.5 nm)硫化鎘結構之過程中，我們發現此核殼量子點之吸收會受到硫化鎘之影響而在短波長大幅提升，但放光仍維持在長波長紅外光範圍，此ㄧ特殊的光學性質預期在下轉換發光(LDS)及螢光太陽能集中器(LSC)之開發上有相當好的潛力，轉換後的紅外光可符合矽太陽能電池的吸收波段並產生電能。

Colloidal PbS quantum dots (QDs) have been studied extensively for their size-tunable infrared emission. Due to their unique electronic and optical properties, PbS QDs provide prominent potential for optoelectronic applications (e.g., solar cells, light-emitting diodes, and luminescent solar concentrators). In this work, we prepare PbS QDs with emission wavelength between 950 to 1600 nm by varying the synthetic parameters such as the reaction temperature, precursor molar ratio, and reactivity of precursors in a viscous system. Hereafter, we synthesize core/shell PbS/CdS QDs by the cation-exchange process using PbS as cores. The enhancement of PL intensity can be observed owing to the effective shell passivation of the PbS surface evidenced by the surface chemistry study. Furthermore, it is found that thicker CdS shell (i.e., > 1.5 nm) grown at a higher shelling temperature (i.e., > 150 °C) results in an increasing absorbance in the shorter wavelength below 500 nm. These unique optical properties may provide potential in some specific applications such as luminescent down-shifting (LDS) or luminescent solar concentrators (LSC).

Abstract i
中文摘要 ii
Table of Contents iv
I. Introduction 1
1.1 Semiconductor nanocrystal 1
1.2 Classical nucleation 3
1.3 Classical growth 6
1.4 Ostwald ripening 8
1.5 Core-type quantum dots 9
1.6 Core-shell quantum dots 10
1.7 Infrared quantum dots 12
II. Literature Reviews 13
2.1 PbS quantum dots 13
2.2 PbS/CdS core/shell QDs 18
2.3 Applications of PbS-based QDs 22
2.4 Motivations of this work 25
III. Experimental 26
3.1 Nanocrystal synthesis 26
3.1.1 Materials 26
3.1.2 PbS QDs Synthesis 26
3.1.3 Purification/Ligand Exchange 28
3.1.4 PbS/CdS core/shell QDs synthesis 28
3.2 Characterization 30
3.2.1 Ultraviolet-visible absorption spectroscopy (UV-Vis) 30
3.2.2 Photoluminescence spectroscopy (PL) 31
3.2.3 X-ray diffraction (XRD) 32
3.2.4 Transmission electron microscopy (TEM) 34
3.2.5 X-ray photoelectron spectrometer (XPS) 36
IV. Results and Discussion 38
4.1 Synthesis of PbS QDs 38
4.1.1 Size tunable infrared PbS QDs 38
4.1.2 Optical properties of PbS QDs 49
4.1.3 Surface chemistry of PbS QDs 51
4.2 Synthesis of PbS/CdS core/shell QDs 56
4.2.1 Optical properties of PbS/CdS QDs 56
4.2.2 Characterization of PbS/CdS QDs 61
4.2.3 Surface Chemistry of PbS/CdS QDs 64
4.2.4 PbS/CdS QDs with thicker shell 68
V. Conclusions 90
VI. References 92

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