有序奈米銀線結構自組裝設計並應用於應變感測器與太陽能電池

Abstract

由於排列和圖案化的奈米銀線具有多元豐富的應用，近年來關於其製程研究越來越受到重視。銀線薄膜具有高導電性、可撓性、高散射強度、和奈米金屬線的高比表面積等眾多優異的材料特性，適合應用於光學與感測元件。當銀線組裝整合於非傳統基板時則可擴展出更多的應用，像是有可拉伸基板的應變感測器。 本篇論文中有兩部分主題分別是「於聚二甲基矽氧烷基板上圖案化與排列奈米銀線並應用於應變感測器」與「奈米銀線陣列之排列與轉印並應用於太陽能電池」。關於應變感測器的部分，已有許多文獻探討製做奈米銀線圖案的方法並應用於應變感測器，然而大部分其元件結構複雜，製程繁多、高成本且耗時。為此我們開發了新製程「室溫表面處理結合模板圖案法」在矽膠基板上製做電極圖案，同時利用應力釋放法將圖案內的銀線進行排列。製程設計簡易快速、低成本，且解決高分子基板在傳統製程中容易受機械力和溫度影響之限制。我們利用光罩與氧電漿處理製做寬250微米(最小可至100微米)的蛇形銀線電極，緊接著利用應力釋放法排列出具方向性的銀線陣列。應變感測器的彎曲測試結果顯示，電流變化量幾乎隨著應變做線性變化且應變係數為6.4。 關於銀線陣列在太陽能電池應用方面，我們的目標為沉積奈米銀線陣列於太陽能電池表面以提升光電轉換效率。我們已利用介電泳力法在指叉狀電極上排列出理想的奈米銀線陣列，然而當直接於有金字塔抗反射層結構的太陽能板上排列銀線時則影響排列效果。我們整合了排列與轉印之技術以解決基板的限制，製程成本低且快速，並且可應用於大面積的奈米線陣列轉印，甚至可以彈性地發展其他非傳統基板的奈米線整合元件。

In the past decade, the development of fabrication processes for aligning and pattering of silver nanowires (AgNWs) has accelerated dramatically, owing to their unique structures and various potential applications. Silver nanowires have many excellent features that bring forth the potentiality for sensing and optics applications, such as low resistivity, flexible properties, high scattering efficiency and high surface area ratio of metal nanowires. When materials are assembled to an unconventional substrate, they could be extended to much more applications, such as strain sensor with stretchable substrates. There are two parts in this study, “Patterning and Arranging Silver Nanowires on Polydimethylsiloxane (PDMS) for Strain Sensor” and “Alignment and Transfer Printing of Silver Nanowires Arrays for Solar Cell Application”. As far as strain sensor is concerned, various methods to pattern and print AgNWs on PDMS for strain sensor have been demonstrated in previous work, however, the complicated structures and sophisticated fabrication processes presented were expensive and time consuming. Therefore, a novel strategy “room-temperature surface treatment stencil patterning method” to print AgNWs electrode patterns on PDMS substrate is presented in this study with AgNWs aligned in the patterns by strain-release assembly method in the meanwhile, whose design is simple, low cost, fast, and overcomes mechanical and thermal restrictions of traditional microfabrication technologies. In detail, AgNWs serpentine electrodes with 250 µm wide (be able to 100 µm) are fabricated by utilizing shadow mask and oxygen plasma treatment, followed by aligning AgNWs in the same direction via strain release assembly methods. The bending test results of the strain sensor show that the fractional change in electrical current is close to linear with the strains, and the gauge factor is 6.4. As for AgNWs arrays for solar cell applications, our goal is to deposit AgNWs arrays on solar cell for enhancing photovoltaic conversion efficiency. The resulting alignment is ideal when AgNWs arrays are aligned on interdigitated electrodes by dielectrophoresis force in previous experiments, but not for aligning AgNWs arrays directly on silicon solar cell with pyramidal structure texture. In order to solve the limitations, integrating the alignment with transfer printing technique is adopted, and the fabrication approach is low-cost, fast, and scalable to large area NW arrays, which offers flexible applications for developing NW-based devices with unconventional substrates.