利用奈米金屬團簇製備奈米結構於光電元件之應用

Abstract

抗反射層由於能夠減少表面反射增加入光量，在太陽能電池中扮演著重要的角色。但入射太陽能電池的光線並不全是垂直元件表面，抗反射層能否在大入射角度時還保持著同樣優良的抗反射效果便成了重要的議題。在本篇論文中我們利用兩種方式來製作寬波段廣角度的抗反射層，第一種則是利用侵入式奈米金團簇蝕刻粗糙化矽基板製作微米奈米複合結構，藉由光學量測可以得知其擁有非常良好的寬波段廣角度抗反射效果，在垂直照射時平均反射率僅1.64%，在各種角度照射的情形下都擁有比市售太陽能電池抗反射層更好的抗反射特性。除了優秀的抗反射特性之外，利用侵入式奈米金團簇作為觸媒再配合超音波震盪進行蝕刻可以大幅加速蝕刻反應，使我們可以在數秒鐘之內得到特性良好的抗反射層。另一種是利用多層介電質薄膜結合粗糙化矽基板製作自我複製結構，針對不同情況我們設計了具結構的光學薄膜，透過模擬計算可以得知該結構比一般市售太陽能電池的抗反射層擁有更好的抗反射效果，透過實際在市售太陽能電池上外加我們所設計之光學薄膜，太陽能電池所輸出的光電流在任何入射角度情形下皆有所提升。 另外針對新穎的侵入式奈米金團簇，我們對其基本性質作一些探討，例如矽基板上原生氧化層厚度對其分佈密度的影響、後續熱處理對其分佈的影響以及侵入式奈米金團簇能夠提升蕭特基矽光偵測器的偵測力(Detectivity)等。另外我們利用侵入式奈米金屬團簇來蝕刻氮化鎵基板，並觀察到侵入式奈米金屬團簇亦能夠催化蝕刻液對於氮化鎵的蝕刻反應，藉由光致發光(PL)光譜能夠得知這些蝕刻的結構能夠有效地提升氮化鎵的光萃取效率，具有結構的氮化鎵出光量可以達到原先的1.72倍。

The antireflective coatings play an important role in solar cells due to its ability to reduce the reflection of light from the solar cell surface, and thus increase the light harvesting of solar cells. However, the incident angles of incoming light are not always normal to the solar cell surface. Therefore, to remain the great antireflective characteristic at large incident angles for the antireflective coatings become an essential issue. In this study, we fabricate the broadband omnidirectional antireflective structures in two ways. The first method is that we utilize the intruded gold nanoclusters (INC) to prepare micro-nano hybrid structures on a silicon substrate. The hybrid structures display great broadband omnidirectional antireflective characteristic, and the average reflectance is down to 1.64% under normal incidence. Besides, the reflectances of the hybrid structures under various incident angles are lower than that of the antireflective structures on conventional solar cells. Moreover, combining the INC method and the ultrasonic etching process can result in much faster process for preparing antireflective structures, making us obtain excellent antireflective structures within just a few seconds. The other method is to deposit dielectric multilayer films on textured silicon substrate for fabricating the autocloning structures. We design two kinds of autocloning structures, and we conclude from the simulation results that these structures exhibit better antireflective characteristic than that of the antireflective structures on the conventional solar cells. By applying the designed optical thin films onto a commercial solar cell, we found the photocurrent of the solar cell was increased at all incident angles. In the last, we studied the mechanisms of novel INC method, such as the influence of native oxide thicknesses on the distribution of the nanoclusters, the effect of thermal treatment on the distribution of the nanoclusters, and to enhance the detectivity of a schottky photodetector. Besides, we utilized the INC method to prepare textured structure on GaN substrates. And we have proved that the INC-assisted etching of GaN is practical as well. According to the photoluminescence (PL) measurement, we observed that these textured structures can enhance the light extraction efficiency on GaN surface, and the PL intensity can be increased by a factor of 1.72.