石墨烯與奈米材料複合紫外-可見光光感測器特性之研究

傳統的雙波段，多波段或是多色光偵測器，由堆疊兩種或多種吸光材料並透過帶間與帶間躍遷之機制來進行光偵測及訊號的產生，然而其製程繁雜，光響應表現亦不顯著。在此研究中我們將化學氣相沉積法製成之石墨烯置於氧化鋅奈米粒子(ZnO nanoparticles)與聚(3-己烷基噻吩)(P3HT)之間，熱平衡狀態下此兩種材料間形成P-N 異質接面之能帶彎曲，極薄的石墨稀則存在於接面的內建電場中。元件在照光下於個別材料中產生電子電洞對，由於兩個材料之於石墨烯之能帶彎曲不同，不同的載子受到電場驅動進而對石墨稀進行不同的摻雜。我們成功地利用這樣特殊的異質結構，並且結合了石墨烯的絕佳導電性與半導體量子點的高度光吸收進而達成了高光感度，及在波長小於400 nm和大於400 nm 之光的照射下，分別有著上升光電流與下降光電流的特殊結果。這使得我們的元件不只可以偵測紫外光與可見光的存在，亦可以區分其波長在可見光(> 400 nm)區間或是紫外光區間(< 400 nm)，再者由於材料的可彎曲特性，亦使元件可以在彎曲的情況下保持其效果，並在未來能進一步地被應用於穿戴裝置中。

關鍵字

二維材料；石墨烯；高響應率；氧化鋅；光偵測器；聚(3-己烷基噻吩) ；異質接面；可彎曲元件

並列摘要

Traditional dual-band, multi-band or multi-color photodetectors are fabricated by stacking two or more light-absorbing materials, which utilize the mechanism of inter-band/inter-band transition for light detection and signal generation, however, the process of fabrication is complex, and the photoresponse is low. In this study, we proposed a new device composed of a graphene layer synthesized by chemical vapor deposition (CVD) process between ZnO nanoparticles (ZnO NPs) and the poly (3-hexylthiophene) P3HT layer. By using such a three-layered heterojunction combined with the excellent conductivity of graphene and high absorption of semiconductor quantum dots and P3HT, we successfully achieved a photodetector with high sensitivity and dual photoresponses. In addition, this unique structure enables the detector not only to detect a wide spectral range spanning from ultraviolet to visible, but also exhibits dual photoresponses, the visible (> 400 nm) in which a positive photocurrent is obtained, while in the ultraviolet (< 400 nm) a negative photocurrent is measured. The underlying mechanism responsible for these intriguing behaviors has been developed based upon the band alignment of the heterostructure. Besides, due to the flexibility of all the constituents, the device possesses flexible characteristics, which is very useful for the development of the future integrated wearable systems.

並列關鍵字

two-dimensional material ； graphene ； high photoresponse ； zincoxide ； photodetector ； poly (3-hexylthiophene) ； heterojunction ； flexible device

參考文獻

Chapter 1 Introduction

2. Mueller, T.; Xia, F.; Avouris, P., Graphene photodetectors for high-speed optical communications. Nature Photonics 2010, 4 (5), 297-301.

3. Park, J.; Ahn, Y. H.; Ruiz-Vargas, C., Imaging of Photocurrent Generation and Collection in Single-Layer Graphene. Nano Letters 2009, 9 (5), 1742-1746.

4. Xia, F.; Mueller, T.; Golizadeh-Mojarad, R.; Freitag, M.; Lin, Y.-m.; Tsang, J.; Perebeinos, V.; Avouris, P., Photocurrent Imaging and Efficient Photon Detection in a Graphene Transistor. Nano Letters 2009, 9 (3), 1039-1044.

7. Haider, G.; Roy, P.; Chiang, C.-W.; Tan, W.-C.; Liou, Y.-R.; Chang, H.-T.; Liang, C.-T.; Shih, W.-H.; Chen, Y.-F., Electrical-Polarization-Induced Ultrahigh Responsivity Photodetectors Based on Graphene and Graphene Quantum Dots. Advanced Functional Materials 2016, 26 (4), 620-628.

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石墨烯與奈米材料複合紫外-可見光光感測器特性之研究

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