先進可穿載式光電元件之研究與應用

Design, fabrication, characterization, and application of advanced wearable optoelectronic devices

胡瀚文(Han-Wen Hu)

指導教授 ： 陳永芳

國立臺灣大學/理學院/物理學研究所/博士(2019年)

https://doi.org/10.6342/NTU201701770

摘要

近年來，因應科技快速的發展，電子及光電產業都致力於研發具備更多新特性的元件，此論文中，我們設計、製程以及展示了可用於電子皮膚中，可撓與多功能的新穎光電元件，我們相信這些新穎的設計能帶給下世代穿載式元件的研究發展很大的作用。本論文包含三個主題，其摘要如下:
1. 利用壓電效應和可撓式量子點發光二極體之互動式變色電子皮膚
啟發於變色龍、青蛙、頭足類動物等自然界動物，改變皮膚顏色的能力可以用於偽裝、警示、視覺通訊，而引起了大家強烈的興趣。電子皮膚能藉由量化外在的刺激模仿生物皮膚，到今日，對能模仿可變色之電子皮膚的研究以感測器和顯示器陣列的整合來完成，而需要繁複的製程，本研究中，我們首次展示了單一元件作為能隨施加壓力變化顏色的互動式電子皮膚，製程的方法有效節省成本和空間，因此對發展下世代具備視覺回饋的電子皮膚有非常大的幫助。
2. 皺褶結構二維材料作為可拉伸且低閾值隨機雷射的多功能平台
具有可拉伸、可彎曲、以及寬頻譜的隨機雷射系統在下一代技術中具有許多潛在的可應用性，例如可見光通訊，超高亮度固態照明，生物醫學研究，螢光等等。然而，可拉伸雷射元件所需的共振腔製成一直是個困難，因為一般用來產生同調性輸出的共振腔都不具延展性。二維材料有高延展性的優勢，在行成皺褶結構下可以在結構的峰谷間侷限光子。此研究中，我們分別利用有皺褶的石墨烯碎片、單層石墨烯和多層氮化硼，設計了具有超低閾值的可拉伸和可穿戴隨機雷射元件。並使用鈣鈦礦奈米晶體（PNC）來說明我們的原理，發現雷射閾值為〜10 µJ/cm2，比現有報導的隨機雷射最低值低了大約兩倍。除了PNC之外，我們還證明了可以使用不同的主動材料（例如半導體量子點）來調整輸出的雷射波長。 因此，此研究對未來高效能的可穿戴光電元件的發展非常有幫助。
3. 利用全反射之超低閥值無共振腔雷射元件
在波傳遞碰到物質邊界時，全反射是個最重要的現象，能廣泛應用從光通訊到螢光顯微鏡，也常在傳統雷射的共振腔中被利用。近年來，在無序介質中無共振腔雷射的物理現象，像是光的安德森侷限到散斑成像，得到了很大的關注，然而，有別於傳統雷射，全反射並未被研究於隨機分布介質中引起的雷射中，因此，我們用空氣泡作為散射中心來展示出一個超低閥值的無共振腔雷射系統，光在空氣泡表面的全反射能大幅減少能量的損失而增強光的放大效應，我們的方法提供了很好的方案來調控光的能量流動，以達到超低閥值的無共振腔雷射系統，對高效能光電元件的發展提供很好的方向。

關鍵字

電子皮膚 ； 互動式元件 ； 隨機雷射 ； 二維材料 ； 全反射

並列摘要

Over the last several decades, electronic and optoelectronic industries are going through a major paradigm shift for the development of devices with new characteristics to meet the desire of rapid growth of science and technologies. In this thesis, we have designed and demonstrated new flexible and multi-functional optoelectronic devices for electronic skins, which shows the great potentials for the development of next-generation wearable electronics. Our results are classified as three main topics and summarized as follows:
1. Interactive color-changing electronic-skin based on flexible and piezoelectrically tunable quantum dots light emitting diodes
Inspired by animals in nature, such as chameleons, frogs, and cephalopods, the remarkable capability of changing one’s skin color has drawn considerable interests due to its wide applications in camouflage, warning methods, and visual communications. Today, research on electronic skins (e-skins), imitate biological skin by quantifying external stimuli, to mimic this unique color-changing function has been achieved based on the integration of a matrix of displays and sensors; however, integrated systems possess bulky and complicated fabrication processes. Here, we make the first attempt to demonstrate a single user-interactive e-skin device with color-changing response upon applied external strain, while using a cost-effective and space-saving method, which promises to open new possibilities for the development of next-generation e-skins with the visual response.
2. Wrinkled Two-dimensional Materials: A Versatile Platform for Low-threshold Stretchable Random Lasers
A stretchable, flexible, and bendable random laser system capable of lasing in a wide range of spectrum has many potential applications in next-generation technologies, such as visible-spectrum communication, super-bright solid-state lighting, biomedical studies, fluorescence, etc. However, producing an appropriate cavity for such a wide spectral range remains a challenge owing to the rigidity of the resonator for the generation of coherent loops. Two-dimensional materials with wrinkled structures exhibit superior advantages of high stretchability and a suitable matrix for photon trapping in between the hill and valley geometries compared to their flat counterparts. In this study, we utilize the intriguing functionality of wrinkled reduced graphene oxide, single-layer graphene, and few-layer hexagonal boron nitride, respectively, to design highly stretchable and wearable random laser devices with the ultra-low threshold. Using methyl-ammonium lead bromide perovskite nanocrystals (PNC) to illustrate our working principle, the lasing threshold is found to be ~ 10 µJ/cm2, about two times less than the lowest value ever reported. In addition to PNC, we demonstrated that the output lasing wavelength can be tuned using different active materials such as semiconductor quantum dots. Thus, our study is very useful for the future development of high-performance wearable optoelectronic devices.
3. Ultra-low Threshold Cavity-free Laser induced by Total Internal Reflection
Total internal reflection is one of the most important phenomena when a propagated wave strikes a medium boundary, which possesses a wide range of applications spanning from optical communication to fluorescence microscope. It has also been widely used to demonstrate conventional laser actions with resonant cavities. Recently, cavity-free laser actions have attracted a great attention due to several exciting physical phenomena in disordered media, ranging from Anderson localization of light to speckle free imaging. However, unlike conventional laser systems, total internal reflection has never been implemented in the study of laser action derived from randomly distributed media. Herein, we demonstrate an ultra-low threshold cavity-free laser system using air bubbles as scattering centers, in which the total internal reflection from the surface of air bubbles can greatly reduce the leakage of the scattered beam energy and then enhance the light amplification within a coherent closed loop. Our approach provides an excellent alternative for the manipulation of optical energy flow to achieve ultra-low threshold cavity-free laser systems, which should be very useful for the development of high-performance optoelectronic devices.

並列關鍵字

Electronic-skin ； User-interactive Device ； Random Laser ； Two-Dimensional Materials ； Total Internal Reflection

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