本論文研究分為兩大部份分別是利用溶液法合成改善Ⅳ-Ⅵ族硫化鉛(PbS)半導體量子點材料，以及PbS量子點薄膜蕭特基太陽能電池之元件製程之優化，以提升元件整體之光電轉換效率。
第一部分量子點材料之改善，首先以不同OA-PbO比例合成不同尺寸的PbS量子點(直徑3, 3.5, 4.1, 5.6 nm)，並且利用溫度調控製備最優化之PbS量子點材料，最後利用混和溶劑以及高速離心的方式，合成具有高產率之小尺寸奈米粒子(~ 3.5 nm PbS)。此優化的PbS量子點材料，因量子侷限效應的影響之下，具有第一激子能量(~ 1.44 eV)，應用於ITO / PEDOT: PSS / PbS / Al 結構之蕭特基太陽能光伏元件上，可以同時擁有較高的開路電壓(~ 0.43 eV)以及短路電流密度(~ 12.5 mA/cm2)，因而能提高整體光電轉換效率達2.02 ％。
此外透過AFM以及SEM分析發現結合PEDOT: PSS電洞傳輸層於元件中，具有降低基板的粗糙度以及提升元件界面之接合，因此提升元件製程良率。其次，透過調控到最適當的薄膜厚度，使元件展現最佳短路電流密度，同時具有較高的吸光能力以及降低電子電洞對的再復合。接者，我們利用FTIR、SEM、TEM分析，發現藉由1, 2-乙二硫醇(EDT)處理之PbS量子點薄膜，其表面的油酸(OA)長碳鏈官能基有效被取代成短碳鏈，使得量子點之間的距離能有效縮短，進而改善光伏元件之載子傳輸能力以及提高光電元件之轉換效率。最後，我們透過導電度、XPS分析探討熱退火對於量子點薄膜元件電性上的影響。我們發現最佳熱退火條件能使PbS量子點表面長碳鏈官能基脫附，造成量子點之間的距離下降以增加薄膜的導電度，且具有較少的缺陷(PbSO4)能降低電子電洞對再復合。透過一系列材料本質以及元件結構的改善能具有最佳的光電轉化效率高達2.52％。

This thesis focused on two parts: (1) Improving solution process synthesis of Ⅳ-Ⅵ lead sulfide (PbS) semiconductor quantum dots (QDs). (2) Fabricating Schottky solar cells based on PbS nanocrystals and optimizing the efficiencies of PbS Schottky photovoltaic device.
First, the syntheses of PbS QDs with different sizes were obtained by using different proportion of OA-PbO and controlling temperature. The different diameter of PbS quantum dots were 3, 3.5, 4 and 5.6 nm, respectively. Finally, the high yield of PbS nanocrystals with small size (~ 3.5nm) was also obtained by using the mixed solvent approach with high-speed centrifugation. The PbS quantum dots with small size have the first exciton energy is 1.44eV due to quantum confinement effects. The PbS quantum dots with small size were applied to fabricate PbS NCs Schottky solar photovoltaic device which is based on structure of ITO / PEDOT: PSS / PbS / Al. The device demonstrated high open circuit voltage (~ 0.43eV) and large short circuit current density (~ 12.5mA/cm2). The overall efficiency of PbS Schottky solar cell was improved and reached to 2.02%.

To optimize the efficiency of PbS NCs Schottky Solar cell, the PEDOT: PSS polymer film was used as a hole transported layer between ITO and PbS NCs film. According to analysis of AFM and SEM measurement, the PEDOT: PSS polymer film smoothed the ITO substrate and lower roughness. Therefore, the yield rate of PbS NCs devices was increased. Second, the high short-circuit current density was obtained by tuning appropriate thickness of PbS NCs film which caused high absorption ability and reduced the recombination of electron-hole pair. Because the as-synthesized PbS NCs were usually passivated with ~2.5 nm long alkyl ligands (OA), which may prevent close nanocrystal packing of PbS thin films and thus, impede charge transport. The PbS NC films were treated by ethanedithoiol (EDT) to remove the long chain ligands from NC surfaces and reduce interparticle spaces of NCs, resulting in improve the carrier transport ability of the photovoltaic device. Finally, the electrical property of PbS NCs thin film was affected by thermal annealing process. We found that the surface functional groups of PbS NCs can be desorbed during thermal annealing process, resulting in decreased distance between the quantum dots to increase the conductivity of the film. During thermal annealing process, deep traps (PbSO4) in PbS NCs were found and reduced the recombination of electron-hole pair. Overall results showed that to the quality of NCs and device structures can be improved by controlling various condition. The best photoelectric conversion efficiency was up to 2.52％.

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