近年來，隨著智慧行動裝置與可撓穿戴式裝置的發展，紅外光感測技術已經逐漸有大量新興應用領域，例如成像感測、光通信感測、心跳/血氧偵測。紅外光量子點硫化鉛（PbS）具有以下優點：可調的材料能帶、簡易製程、低生產成本以及對柔性基板的適用性。在本研究中將會探討使用液相配體交換方法製造元件之載子收集能力，光偵測元件外部量子效率為42.75 %，透過分析結果，發現表面容易氧化形成缺陷。而採用另外一次鹵素鈍化方法的光偵測器，在優化薄膜品質以及材料表面化學鈍化後，鹵素鈍化之光偵測元件最終提升外部量子效率至52.62％以及其響應度至0.399 A / W，開發出可量產且低成本的PbS 製備方式，在未來商業化深具潛力。

In recent years, personal wearable devices have gained popularity owing to new technological advances. The photodetectors for IR light detection have a vast number of emerging application areas, such as imaging, light communication, heartbeat detection. The lead sulfide (PbS) quantum dots have several advantages such as size-tunable optical bandgaps, simple solution process abilities, low production cost, low operative temperature, high air stability and suitability for the flexible substrate. In this study, the carrier extraction ability of the device is investigated via liquid-phase ligand exchange method, and the performance of photodetectors shows the external quantum efficiency to 42.75%. According the analysis, the oxidation easily occurs without passivation during ligand exchange process. After optimizing the quality of the film and the chemical passivation of surface, photodetectors based on one-step synthesis finally increase the external quantum efficiency to 52.62% and its responsivity to 0.399 A/W owing to excellent passivation with halide ligands. The low-cost manufacturing of PbS ink has potential for commercial application in the future.

中文摘要 ................................................2
Abstract ................................................3
Chapter 1 Introduction ..................................8
Chapter 2 Literature Review .............................12
2.1 Architecture design of photodectors ..............12
2.2 Key figure-of-merit parameters of photodetectors ....14
2.3 Composition and Structure characterization ..........16
2.4 Photovoltaic device .................................20
2.4.1 Liquid-state ligand method ........................20
2.4.2 Solid-state ligand exchange (LBL)..................22
2.5 Architecture design of IR-PDs prepared from PbS .....25
2.6 Interfacial layers improvement in PbS PDs ...........29
2.7 Surface modification and characteristics control of PbS PDs .........................................................33
Chapter 3 Experimental Method............................37
3.1 Chemicals ...........................................37
3.2 Device fabrication ..................................37
3.2.1 Substrate cleaning ................................37
3.2.2 Fabrication of electron-transport layer (ETL) .....38
3.2.3 Fabrication of hole-transport layer (HTL) .........38
3.3 Fabrication of PbS ink with ligand exchange method ..38
3.4 One-step direct synthesis of PbS-I ..................39
3.5 Instruments .........................................39
3.5.1 Photoluminescence Spectroscopy ....................39
3.5.2 UV-vis absorption Spectroscopy ....................39
3.5.2 X-ray Powder Diffraction ..........................40
3.5.3 Scanning Electron Microscopy (SEM) ................41
3.5.4 Atomic force microscopy (AFM) .....................42
3.5.5 X-ray Photoelectron Spectroscopy (XPS) ............42
3.5.6 External quantum efficiency (EQE) .................43
Chapter 4 Results and Discussion ........................44
4.1 The improvement of PbS films after ligand exchange process .........................................................44
4.1.1 Characterization of as-received PbS QDs ...........44
4.1.2 The improvement of colloidal stability of PbS after ligand exchange ................................................46
4.1.3 The surface morphology analysis of PbS films after ligand exchange ................................................50
4.1.4 Influence of experimental parameters in PbS films after ligand exchange ......................................54
4.2 Effect of thickness on the performance of PDs .......59
4.2.1 Optoelectronic characterization of PDs based on the ligand exchange method .........................................59
4.2.2 The other parameters of PDs based on the ligand exchange method ..................................................63
4.3 The influence of surface chemistry for PbS devices ..66
4.4 One-step direct PbS capped halide synthesis .........71
4.4.1 Characterization of direct PbS capped halide synthesis..71
4.4.2 Optoelectronic characterization of PDs based on one-step direct PbS synthesis ....................................75
4.5 The influence of surface chemistry for PbS devices based on direct synthesis ........................................81
Chapter 5 Conclusions ...................................85
References ..............................................86

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