以電化學沉積法製備氧化鋅奈米結構表面於自潔表面與光伏特元件之應用

Synthesis of Zinc Oxide Nanostructures by Electrodeposition for Application of Self-cleaning Surfaces and Photovoltaic Devices

楊叔瑛(Shu-Ying Yang)

指導教授 ： 謝建德

元智大學/工程學院/化學工程與材料科學學系/碩士(2007年)

https://doi.org/10.6838/YZU.2007.00035

摘要

本研究第一部分使用陰極電化學沉積法在已製備好氧化鋅成核層之銦錫氧化物(ITO)基板上生長不同高度且垂直排列的氧化鋅奈米棒陣列，而此實驗所使用的電鍍液為硝酸鋅溶液，操作溫度於60 °C與80 °C。此方法製備之ZnO奈米棒為纖鋅礦晶體結構且不同電沉積時間可以很好地控制其高度，若經氟化塗層後可得到具超疏水特性的氧化鋅奈米棒，其接觸角之最大值可達166.9°。超疏水現象是由於空氣層被受限於奈米棒陣列中，使得水滴坐落在氧化鋅奈米棒的表面上，此稱為Cassie狀態。由本研究發現，其水接觸角隨氧化鋅奈米棒的高度，從99.8到746 nm而有所不同，以本研究推導出的model可很好的預測氧化鋅表面的超疏水特性，能夠確定氧化鋅棒的沾溼比例，此結果將揭示氧化鋅奈米棒陣列之高度變化將如何影響其超疏水行為。
以陰極電化學沉積法，電沉積溫度在60–80°C之間於ITO玻璃上所製備之一維氧化鋅奈米晶體具有不同的形態與晶體結構。本研究第二部份設定五個實驗參數，包括：成核層之密度、電沉積電壓、成長溫度、沉積時間、退火溫度，不同實驗參數都會影響氧化鋅奈米柱陣列在ITO基材上的成長。我們由XRD、FE-SEM、HR-TEM、XPS來分析氧化鋅奈米柱結構的變化。隨著電沉積電壓、成長溫度、沉積時間、退火溫度之遞增，氧化鋅奈米柱以c軸為優先成長方向就越明顯，且仍為纖鋅礦結晶結構，而(002)晶面之間距約為2.6 Å。研究中以Arrhenius-typ的分析，電沉積溫度60–80°C之不同活化能27.5 kJ/mol (沉積時間5分鐘) < 41.8 kJ/mol (沉積時間10分鐘) < 46.1 kJ/mol (沉積時間20分鐘)來解釋氧化鋅多階段增長機制。實驗參數提供了於導電基材上低溫製成理想形態之氧化鋅奈米柱，最後，將其應用於高分子太陽能電池中，並建立一個組裝高分子太陽能電池之操作平台，以利未來做更深入的研究。

關鍵字

纖鋅礦晶體結構 ； 超疏水 ； 氧化鋅 ； 電化學沉積 ； 奈米棒 ； 接觸角 ； 高分子太陽能電池

並列摘要

Vertically aligned ZnO nanorod arrays with different heights were grown on a ZnO seeded indium tin oxide substrate by cathodic electrochemical deposition from zinc nitrate at two temperatures of 60°C and 80°C. As-grown ZnO nanorods exhibit wurzite crystal structure and their heights can be well controlled by different deposition times. The fluorination coating tends to induce a superhydrophobicity of ZnO nanorods, i.e., the maximal value of contact angle: 166.9°. The super water repellency can be attributed to the fact that an air layer is confined to the nanorod arrays, and thus leads to water droplets sitting on the ZnO surfaces, referred to as the Cassie state. Interestingly, their water contact angles are found to vary with the heights of ZnO nanorods, ranging from 99.8 to 746 nm. The superhydrophobicity of ZnO surfaces can be well predicted by a proposed model that is capable of determining the wetted fraction of ZnO pillars. This satisfactory result would shed light on how the variation in rod height would induce the superhydrophobic behavior of ZnO nanorod arrays.
One-dimensional ZnO nanocrystals with various textures and crystalline structures have been fabricated on indium tin oxide (ITO) substrates by using cathodic electrodeposition at 60–80°C. Five sets of parameter settings, including seed layer density, applied potential, growth temperature, deposition period, and annealing temperature, are found to vary the growth of ZnO nanorod arrays on ITO substrates. The structural transformation of as-grown ZnO nanorods is characterized by X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electro microscopy, and X-ray photon spectroscopy. The preferential textured growth (i.e., c-axis) of electrodeposited ZnO nanorods from aqueous electrolyte shows an increase with increasing deposition potential, growth temperature, deposition period, and annealing temperature. The resulting ZnO nanorods display wurzite crystal structure and the crystalline rods grow preferentially in (002) direction according to a small integral intensity ratio of (101)/(002). The spacing between adjacent lattice fringes is approximately 2.6 Å, which is close to the interspacing of d002 plane. The analysis of Arrhenius-type plots evidences a multiple-stage growth mechanism according to different apparent activation energies that have an order: 27.5 kJ/mol (period: 5 min) < 41.8 kJ/mol (period: 10 min) < 46.1 kJ/mol (period: 20 min) within 60–80°C. The study on the parameters affecting the ZnO texture offers a great benefit to grow the desired morphology of ZnO nanorods on conducting substrates at low temperature. Accordingly, such for unigue ZnO nanorods, prepared by low-temperature electrochemical deposition, display a promising potential in a variety of applications such as polymeric solar cells. A platform for examining the performance of solar cell will be set up in the future.

並列關鍵字

Wurzite crystal structure ； Superhydrophobicity ； Zinc oxide ； Electrochemical deposition ； Nanorod ； Contact angle ； polymeric solar cell

參考文獻

4. D.E. Carlson. C.R. Wronski, Appl. Phys. Lett.71 (1976).

5. K. Sriprapa, P. Sichanugrist, Photovoltaic Energy Conversion, 3 (2003) 2799.

6. H. Spanggaard, F.C. Krebs, Sol. Energy Mater. Sol. Cells 83 (2004) 125.

9. W. Ma, C. Yang, X. Gong, K. Lee, A. J. Heeger, Adv. Func. Mater. 15 (2005) 1617.

12. Z.L. Wang, J. Phys.: Condens. Mater. 16 (2004) R829.