具超薄氧化層之記憶體與光伏元件

Abstract

在這本篇論文中，我們研究三個具超薄氧化層綠色電子元件，即兩個有機雙穩態元件與一個金氧半太陽能電池。超薄氧化層除了可以幫助實現有機雙穩態的電阻態切換與了解相對應的切換機制之外，也可以降低金半太陽能電池的逆向飽和電流而提升元件的開路電壓。 首先，我們研究具n-type Si/Alq3/Al結構的有機雙穩態元件特性。該元件的雙穩態特性是主要來自Alq3/Al界面的缺陷態。值得一提的是我們可以藉由調控Alq3薄膜沉積鍍率去調整該元件的電性。為了瞭解這些現象，我們利用高解析電子能譜儀分析Alq3薄膜與Alq3/Al介面的化學組成，以及透過原子力顯微鏡與薄膜低掠角繞射解析Alq3薄膜與Alq3/Al介面的特性。 然後，我們研究另一種結構的有機雙穩態元件(p+-Si/Alq3/nanostructured MoOx/Alq3/Al)特性。該元件的雙穩態特性是來自嵌入於Alq3薄膜內的MoOx似奈米團簇對載子捕抓與釋放之現象。當MoOx似奈米團簇捕抓載子後(高導電態)，所形成的空間電荷會主導元件內載子的傳輸機制。我們也探討該元件的雙穩態滯留時間與寫入-讀取-抹除-讀取之特性。 最後，我們提出一個有效提升開路電壓的疊合式金氧半太陽能電池結構，而該疊合式金氧半太陽能電池是由一個n型金氧半太陽能電池與一個p型金氧半太陽能電池所構成。在AM1.5模擬太陽光照射下，該太陽能電池的開路電壓可達0.71V。該開路電壓高於目前已發表的n型或p型金氧半太陽能電池之開路電壓。在此，我們成功地證明利用疊合式金氧半太陽能電池結構提升太陽能電池的開路電壓之可行性。該疊合式金氧半太陽能電池結構將在未來光伏元件應用於水裂解氫能中扮演重要的角色。

In this dissertation, we study three green devices using ultrathin oxide layers: two organic bistable devices (OBDs) and one metal-insulator-semiconductor (MIS) solar cell. The ultrathin oxide layers not only can help realize the resistance switching of the OBDs and recognize the corresponding mechanisms, but also can reduce the reversed saturation current of metal-semiconductor solar cells and thus can ameliorate the open-circuit voltage (Voc) of the solar cells. First of all, the properties of an OBD using an n-type Si/Alq3/Al structure are investigated. The bistable effect of the OBD is primarily caused by the interface defects at the Alq3/Al interface. It is worthy to mention that the electrical properties of the OBD can be modified and controlled by utilizing the appropriate deposition rate of the Alq3 thin film. To understand these phenomena, we use high resolution X-ray photoelectron spectroscopy to analyze the chemical composition of the Alq3/Al interface and Alq3 thin films, and atomic force microscopy and grazing incident X-ray diffraction to characterize the properties of Alq3 thin films. Furthermore, the electrical properties of an OBD with a p+-Si/Alq3/nanostructured MoOx/Alq3/Al structure are also investigated. The bistable switching of the OBD attributes to the charge trapping/erasing in the MoOx nanoclusterlike layer interposed between the Alq3 thin films. After charges are trapped in the MoOx nanoclusterlike layer (the high conductance state), the carrier transportation of the OBD will be dominated by a space-charge field which results from trapped charges. Both the retention measurement and write-read-erase-read cycles of the OBD are also provided. Finally, a stacking MIS solar cell structure, which integrates an n-type MIS solar cell with a p-type MIS one, is proposed to effectively enlarge Voc. The measured Voc is up to 0.71V under simulated air mass (AM) 1.5 illumination (100 mW/cm2). This Voc is larger than those of the n-type or p-type MIS solar cells published. Here we successfully demonstrate the feasibility of the Voc enhancement of MIS solar cells by using a stacking structure. The stacking MIS solar cell will play an important role in photovoltaic application for hydrogen generation.