利用配體修飾量子點表面之特性分析與光電元件應用

Abstract

本篇論文第一部分探討了基於配體修飾的PbS量子點太陽能電池溶液製程方式和元件結構的優化。首先，我們分別從常見的有機小分子配體、鈣鈦礦配體和鹵素配體中選取較為合適的短配體對量子點進行修飾。通過傅氏轉換紅外光譜(FTIR)和X射線光電子能譜(XPS)結果比較分析不同配體修飾對元件性能的影響，從而選取最合適的短配體——TBAI進行後續的實驗。接著，我們對元件結構進行了優化，根據紫外光電子能譜(UPS)結果，分析用EDT置換長碳鏈油酸後的PbS量子點薄膜(PbS_EDT)與MoO3層作為電洞傳輸層在元件結構中的作用。最後，我們討論了主動層（TBAI置換長碳鏈油酸後的PbS量子點薄膜）厚度對元件效率的影響。最終，我們製作出轉換效率為5.74%的PbS量子點太陽能電池。 在第二部分的實驗中，我們製作了元素無毒且含量豐富的三元材料AgBiS2量子點太陽能電池，並通過原子力顯微鏡(AFM)和XPS的分析比較，討論UV-Ozone對電子傳輸層(ZnO)的處理對元件性能的影響。發現，在一定的UV-Ozone處理時間範圍內，元件的光電轉換效率有明顯的上升。 實驗的第三部分主要是AgBiS2量子點在光電探測器上的應用。量子點材料與石墨烯的結合，彌補了單純石墨烯元件的缺點，例如差的光學吸收截面和低的載流子壽命；同時也避免了量子點載流子遷移率低的不足。混合型光電探測器在弱光探測領域具有高的光電導增益和響應率，響應率可達3.33×106 A/W，探測率可達3.48×1014 Jones。

In the first part of this thesis, PbS-based quantum dots (QDs) solar cells were optimized through selecting suitable ligands and structure designing. First, the surface of quantum dots was modified by several short ligands, including small organic ligands, perovskite ligands and halogen ligands. The results of X-ray photoemission spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) consistently indicated that Tetramethylammonium iodide (TBAI) can efficiently exchange oleic acid which is used to stabilize the PbS QDs. Next, we optimized the device structure by introduction of two QDs layers with modification of 1, 2-Ethanedithiol (EDT) and the MoO3 layer as the hole transport layer, and the power conversion efficiency of the optimized solar cells in this study can achieve 5.74%. In the second part, we fabricated non-toxic and earth-abundant ternary AgBiS2 quantum dots solar cells, and discussed the effect of the UV-Ozone treatment on the electron transport layer (ZnO) by atomic force microscope (AFM) and XPS measurements. With UV-Ozone treatment, the power conversion efficiency of AgBiS2 quantum dots solar cells significantly boosted from 1.01% to 2.28%. The third part of the experiment is mainly about the application of AgBiS2 quantum dots on photodetectors. The combination of quantum dots and graphene compensated for the shortcomings of simple graphene components, such as poor optical absorption, and also avoided low carrier mobility of the quantum dots. The hybrid photodetector had high responsivity of 3.33×106A/W and detectivity of 3.48×1014 Jones in weak light detection.