Researches
Our researches are focused on:
- Solar Energy
- ReRAM
- 2D Materials
- Batteries
Solar Energy
Solar cells have drawn much attention as one of the most promising candidates for renewable clean energy. Among all solar materials, Cu(In,Ga)Se2 (CIGS) is the most promising material owing to its excellent light trapping ability, broadband light absorption, and environment-friendly manufacturing processes. An alternative to further improve solar efficiency will highly rely on creation of nanostructure in CIGS thin film because of the broadband and omnidirectional light harvesting characteristics, which can particularly enable higher electron-hole pairs (EPHs), shorter carrier diffusion length, and lower reflectance of device surface, thereby achieving the highest device efficiency. In my lab, we are focusing on the development high efficiency thin film CIGS solar cell based on the sputtering metal alloy allowed by post-selenization proceses. Several research achievements have been developed in my lab. In addition, the management of the light harvesting in Cu(In,Ga)Se2 solar cell with different kinds of were also addressed and developed. Those results have been published in Nano Letters, ACS NANO and Nano Energy already.
銅銦鎵硒與銅鋅錫硫薄膜太陽能電池為目前產學界最受矚目之薄膜太陽能電池材料,而致力於開發第三世代太陽能電池,藉由引入奈米結構、表面電漿子等技術以開發更高效率及低成本之太陽能電池。不同於傳統矽晶太陽能電池,目前此類技術應用於銅銦鎵硒其門檻較高,故仍少有文獻發表,本實驗室已開發引入奈米結構、表面電漿子等技術以開發更高效率及低成本之銅銦鎵硒太陽能電池。例如成功開發大面積(4")製備銅銦鎵硒奈米結構製程技術,利用Ar+離子濺射的原理,快速、低成本且無須模板輔助方式製造大面積、均勻的銅銦鎵硒奈米錐陣列結構(Nanotip Arrays),並將此奈米錐陣列結構做成太陽能元件,並成功提升典型薄膜光電轉換效率,為全世界第一篇利用高能量離子束開發銅銦鎵硒奈米結構製程技術應用於太陽能電池的研究,此外由於離子研磨技術屬半導體業普遍使用之技術,故此成果亦可替將來的CIGS產業,帶來一低成本和高產出的作法;亦引進奈米天線增益技術於銅銦鎵硒吸收層中,由於奈米尺度下規則型貌之奈米粒子可有效散射入射光,使得入射光於元件內之有效光徑增長,進而達到薄吸收層仍維持元件效率表現的目的。以上技術創造之研究成果已發表於ACS Nano等國際知名期刊。此外在CIGS製程技術開發方面,本實驗室亦長期與國家奈米元件實驗室合作,利用電漿硒化技術可以有效裂解、活化硒原子團,增加反應活性,提升薄膜緻密度、平坦度、結晶性及良好元素比例,還有增加CIGS晶粒尺寸、減少硒空缺、使Ga原子均勻分布等優點。開發出電漿輔助製程方式製備大面積合金後硒化CIGS太陽能電池,此平台所製作之CIGS太陽能電池在550 ˚C PESVS可以得到最高轉換效率13.2 %和平均效率11 %,相關成果同共發表於Nano Energy及ACS Applied Materials & Interfaces國際知名期刊。
銅銦鎵硒與銅鋅錫硫薄膜太陽能電池為目前產學界最受矚目之薄膜太陽能電池材料,而致力於開發第三世代太陽能電池,藉由引入奈米結構、表面電漿子等技術以開發更高效率及低成本之太陽能電池。不同於傳統矽晶太陽能電池,目前此類技術應用於銅銦鎵硒其門檻較高,故仍少有文獻發表,本實驗室已開發引入奈米結構、表面電漿子等技術以開發更高效率及低成本之銅銦鎵硒太陽能電池。例如成功開發大面積(4")製備銅銦鎵硒奈米結構製程技術,利用Ar+離子濺射的原理,快速、低成本且無須模板輔助方式製造大面積、均勻的銅銦鎵硒奈米錐陣列結構(Nanotip Arrays),並將此奈米錐陣列結構做成太陽能元件,並成功提升典型薄膜光電轉換效率,為全世界第一篇利用高能量離子束開發銅銦鎵硒奈米結構製程技術應用於太陽能電池的研究,此外由於離子研磨技術屬半導體業普遍使用之技術,故此成果亦可替將來的CIGS產業,帶來一低成本和高產出的作法;亦引進奈米天線增益技術於銅銦鎵硒吸收層中,由於奈米尺度下規則型貌之奈米粒子可有效散射入射光,使得入射光於元件內之有效光徑增長,進而達到薄吸收層仍維持元件效率表現的目的。以上技術創造之研究成果已發表於ACS Nano等國際知名期刊。此外在CIGS製程技術開發方面,本實驗室亦長期與國家奈米元件實驗室合作,利用電漿硒化技術可以有效裂解、活化硒原子團,增加反應活性,提升薄膜緻密度、平坦度、結晶性及良好元素比例,還有增加CIGS晶粒尺寸、減少硒空缺、使Ga原子均勻分布等優點。開發出電漿輔助製程方式製備大面積合金後硒化CIGS太陽能電池,此平台所製作之CIGS太陽能電池在550 ˚C PESVS可以得到最高轉換效率13.2 %和平均效率11 %,相關成果同共發表於Nano Energy及ACS Applied Materials & Interfaces國際知名期刊。
RRAM
Recently, resistive random access memory (ReRAM) has intensively attracted much attention because of its advantages such as non-volatility, high speed, high-density, and low power consumption, which can replace traditional DRAMs used as drivers in next-generation memory. From the material point of view, many metal oxide materials have exhibited switching characteristics at resistive states, such as perovskite-type oxides (e.g., PCMO), ferroelectric oxides (e.g., PTO), and binary transition metal oxides (TMOs). The best switching behaviors of ReRAM devices were observed on the TMOs, such as NiO and TiO2. Among them, ZnO is one of TMOs, exhibiting an excellent resistive behavior. It is a useful material for several applications because of its wide optical direct bandgap of ~3.37 eV and high excitation energy of ~60 meV. Nevertheless, optimized conduction in ReRAM applications for ZnO-based ReRAM is not well investigated yet. We have focused on the development of ZnO-based ReRAM with low power consumption and explore low dimensional metal oxide nanowires for ReRAM application in my lab.
電阻式隨機存取記憶體(RRAM),為最具發展潛力的下一世代新型記憶體,其操作時間短、寫入次數多、耐久性高等絕佳之操作特性,已吸引了產、學界的關注。在電阻式記憶體元件之MIM結構中,透過過渡金屬氧化物(TMO)中原子鍵結缺陷的氧化還原反應,可引發顯著的阻值切換,配合兩極記憶單元、三維堆疊與多位準架構,可實現兆位元級的超高密度非揮發性記憶體技術,但在實際的商業運用上仍有許多關鍵問題需要被解決,利用氧化物中原子鍵結缺陷的氧化還原反應,然而在實際的商業運用上仍有許多關鍵問題需要被解決,而最根本的問題探究方法就是觀察材料結構本身在操作時伴隨或引發的相關變化,最重要的就是缺陷的產生,了解其材料本身作為電阻式記憶體之重要部份,在操作時所發生的行為將可進一步探究其相關機制,以作為電阻式記憶體在材料選擇及設計上的參考,並期許能因此發掘當前可能之問題癥結點。
電阻式隨機存取記憶體(RRAM),為最具發展潛力的下一世代新型記憶體,其操作時間短、寫入次數多、耐久性高等絕佳之操作特性,已吸引了產、學界的關注。在電阻式記憶體元件之MIM結構中,透過過渡金屬氧化物(TMO)中原子鍵結缺陷的氧化還原反應,可引發顯著的阻值切換,配合兩極記憶單元、三維堆疊與多位準架構,可實現兆位元級的超高密度非揮發性記憶體技術,但在實際的商業運用上仍有許多關鍵問題需要被解決,利用氧化物中原子鍵結缺陷的氧化還原反應,然而在實際的商業運用上仍有許多關鍵問題需要被解決,而最根本的問題探究方法就是觀察材料結構本身在操作時伴隨或引發的相關變化,最重要的就是缺陷的產生,了解其材料本身作為電阻式記憶體之重要部份,在操作時所發生的行為將可進一步探究其相關機制,以作為電阻式記憶體在材料選擇及設計上的參考,並期許能因此發掘當前可能之問題癥結點。
Transition Metal Dichalcogenides (TMDCs)
Introduction
We have developed wafer scale of metal-Se2 based TMDCs materials by plasma-assisted chemical vapor reaction (PA-CVR) via the selenization process at the temperature as low as 250 oC and its applications on gas sensor and water splitting. We will further develop different comprehensive research strategies on developing plasma-assisted selenization, sulphurization, telluridization and phosphorization processes on different metal oxides or metals for the synthesis of two dimensional transition metal dichalcogenide materials (2D-TMDs) in a wide range of current and emergent technological applications. We will also develop plasma-assisted chemical vapor deposition (PA-CVD) to grow TMDCs at a low temperature. We will focus on the study starting from development and understanding growth mechanism of material synthesis based on plasma-assisted selenization, sulphurization, telluridization and phosphorization growth to the fundamental properties of these materials by different material characterizations and seeking possible applications based on its unique optical and electrical properties. The applications of these 2D-TMDs will be explored and investigated, including (1) water splitting, HER/OER and CO2 reduction, (2) gas sensor and photodetector, (3) flexible and low temperature electronic devices, (3) anode material in secondary ion battery, (4) diffusion barrier and the transparent electrode by the hybrid TMD/Metal layer. Our novel process can open up a new window for the formation of versatile TMDCs for integration with existing technologies that require lower process temperatures and maintain a manageable thermal budget and being a leading group at this area in the world.
二維材料有優異的電傳輸性質與高撓曲性,使其深具潛力,並應用於下世代的軟性電子與戴式元件。其中石墨烯已被廣泛研究,然而石墨烯之本質上缺乏能隙的情況下,無法製作邏輯電晶體元件,侷限其積體電路之發展。而一種新的半導體二維材料其結構與石墨相似,同屬於橫向有很強的鍵結力而垂直方向僅以微弱的力吸引的層狀材料引起許多科學 家投入研究。這些單層的半導體二維材料如過渡金屬二硫化物擁有直接能隙和壓電特性, 使得過渡金屬二硫化物在各個應用領域,如:產氫、感測和電子元件等,然而,半導體二維材料還缺乏大面積及低溫穩定的合成技術。化學氣相沉積法雖可以獲得高品質的半導體二維材料,但是費時,耗能,高溫及需要另外的轉移步驟,使得半導體二維材料因而侷限其發展。
本實驗室過去幾來建立新穎電漿輔助硒化製程,用於金屬或是金屬氧化物之低溫合成大面積過渡金屬二硫化物硒化物,以建立硫化、碲化、 磷化等新穎電漿化學氣相反應,以低溫合成不同之半導體二維材料大面積合成技術。同時也引入電漿製程氣相沈積法,嘗試低溫成長高品質二維材料,更進行不同半導體二維材料的基礎研究,從材料結構到光學到電子特性等。更進一步進行深入的研究,開發前瞻性、創新性之各式各樣半導體二維材料,亦嘗試實用於光感測器、應變、及氣體感測器、場效電晶體等元件以及水分解產氫、二氧化碳吸附等,另外導入半導體二維材料/金屬層以增加透光度等應用於可撓式透明導電電極,此計劃也藉著斜向沉積法蒸鍍系統嘗試製備具有奈米結構的半導體二維材料,如:奈米線、螺旋狀等結構,研究縮少尺度下物理性質的變化以及其他應用的可能性。
本實驗室過去幾來建立新穎電漿輔助硒化製程,用於金屬或是金屬氧化物之低溫合成大面積過渡金屬二硫化物硒化物,以建立硫化、碲化、 磷化等新穎電漿化學氣相反應,以低溫合成不同之半導體二維材料大面積合成技術。同時也引入電漿製程氣相沈積法,嘗試低溫成長高品質二維材料,更進行不同半導體二維材料的基礎研究,從材料結構到光學到電子特性等。更進一步進行深入的研究,開發前瞻性、創新性之各式各樣半導體二維材料,亦嘗試實用於光感測器、應變、及氣體感測器、場效電晶體等元件以及水分解產氫、二氧化碳吸附等,另外導入半導體二維材料/金屬層以增加透光度等應用於可撓式透明導電電極,此計劃也藉著斜向沉積法蒸鍍系統嘗試製備具有奈米結構的半導體二維材料,如:奈米線、螺旋狀等結構,研究縮少尺度下物理性質的變化以及其他應用的可能性。
Batteries
Introduction
As the most popular energy storage technologies, rechargeable Li-ion, Na-ion, Mg-ion and Al-ion batteries have been widely used in all portable electronic devices. Novel electrode materials for Li-ion, Na-ion, Mg-ion and Al-ion batteries are crucial for suppress the greenhouse gases and enriched the use of renewable energy sources. The TMDs are layered structures similar to graphene offers great potential candidate for use as alternative cathode/anode systems since they are abundant, environmental friendliness, and excellent large-current charge/discharge capability. Notably, TMDs materials which could host/deliver Li/Na/Mg/Al-ions based on the intercalation followed by a redox mechanism. The artificially designed electrodes could create a new way to achieve close to theoretical specific capacity and also to enhance their performance under strenuous charge/discharge rates. In this regard, our NNL lab aims to provide an idea of artificially structural design, construction of 3D-TMDs based composites and the correlation between structure and electrochemical performance, which are matters of grave concern for green energy applications.
Figure source : NATURE MATERIALS | VOL 16 | JANUARY 2017
Figure source : NATURE MATERIALS | VOL 16 | JANUARY 2017
作為最受歡迎的儲能技術,可充電的鋰離子,鈉離子,鎂離子和鋁離子電池已被廣泛用於所有便攜式電子設備中。用於鋰離子電池,鈉離子電池,鎂離子電池和鋁離子電池的新型電極材料對於抑制溫室氣體和豐富可再生能源的使用至關重要。 TMD是類似於石墨烯的分層結構,因為它們含量豐富且對環境無汙染,並具有優異的大電流充/放電能力,所以是作為替代陰極/陽極系統的良好選擇。值得注意的是,TMDs材料可以提供鋰/鈉/鎂/鋁離子進行插層或合金化反應的結構。人為設計的電極可以創造出接近理論比容量的新方法,並且在劇烈的充/放電速率下提高其性能。在這方面,我們的NNL實驗室旨在提供人造結構設計、基於3D-TMDs的複合材料的建構以及結構與電化學性能之間相關性的想法,這也是關於綠能應用上一個嚴重的問題。