光捕捉高分子穿透式奈米碳管網路系統

Light-harvesting Polymers on Percolated Carbon Nanotubes

黃麟智(Lin-Chih Huang)

指導教授 ： 楊長謀

國立清華大學/工學院/材料科學工程學系/碩士(2008年)

摘要

Carbon nanotubes (CNTs) are promising electronic materials, which possess excellent electrical conductivity and great aspect ratios. The CNTs embedded in conjugated polymer host can provide unimpeded paths for electron transport. In this polymer/CNT nanocomposite, excitons were generated on conjugated polymers under illumination and were dissociated at the interfaces of polymer/CNT due to photo-induced electron transfer (PET), where electrons were transported by CNTs and holes were transported through conjugated polymers. In order to explore optoelectronic properties between nanotubes and conjugated polymers in a nanoscale regime, a novel photoelectric material that poly (2-methoxy-5-(2’-ethylhexyloxy)-1, 4-phenylene vinylene) (MEH-PPV) chains grafted with multi-walled carbon nanotubes (MWCNTs) was synthesized via a surface grafting method. The (MEH-PPV)-grafted MWCNTs upon illumination exhibited photo-excited phenomenon and generated significant photocurrents. A Schottky model was used to interpret the observed effect due to variation of the band gap of MEH-PPV and generation of photocurrents. The effect of coating thickness of MEH-PPV was revealed that thicker MEH-PPV enhances larger photocurrent and decreases the occurrence of short circuit. Properties of the organic film solar cell (OSC), where the (MEH-PPV)-grafted MWCNTs was used as the photoactive layer, were also investigated in this research. The preliminary results, where open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF) and power conversion efficiency (η) were 0.355 V, 1.72 mAcm-2, 0.295 and 0.18% respectively, indicate the coating polymer inhibits short circuit and (conjugated polymer)-grafted MWCNTs are promising materials for photovoltaic organic cells.

關鍵字

奈米碳管 ； 太陽能電池 ； 光電高分子

並列摘要

奈米碳管係一種極具潛能的電子材料，其擁有非常優異的導電能力、極大的寬徑比以及與共軛高分子間所產生光誘發電子轉移現象。當將奈米碳管置入共軛高分子材料中，奈米碳管可以提供一個極長且不受阻礙的電子通道進行電子傳遞。在共軛高分子/奈米碳管此種複合材料中，共軛高分子經受光激發後，會產生激子，並於共軛高分子與奈米碳管的界面進行光誘發電子轉移，將激子分離成電子與電洞，其中，電子由奈米碳管傳遞，電洞由共軛高分子傳遞。此種機制可構成有機光伏元件，故奈米碳管應用於共軛高分子基材中，可以提供更多的激子產生體積以及更高的載子傳遞效率。為了研究在奈米尺度下，奈米碳管以及共軛高分子間的光電性質，我們利用表面接支方式合成一新型光電材料－MEH-PPV接枝多壁奈米碳管。經過照光後，MEH-PPV接枝多壁奈米碳管展現出光激發現象以及產生明顯的光電流。本研究中，利用一蕭基接面去解釋MEH-PPV的能間隙對效應、產生光電流的機制以及光誘發電子轉移之現象；MEH-PPV覆蓋厚度效應也同時被探討，其中，在本研究所觀察的範圍內，愈厚的MEH-PPV覆蓋層可以產生愈大的光電流並減少元件短路的發生。最後，將MEH-PPV接枝多壁奈米碳管做為主動層材料，製備一有機太陽能電池，並量測其效率，其量測結果： Voc 為0.355伏特，Jsc為1.72毫安培(每平方公分)，fill factor為0.295，能量轉換效率為0.18%。此初步結果證實藉由表面接枝共軛高分子於多壁奈米碳管表面確實有助於抑制短路的發生，且此一接枝共軛高分子於碳管為一極具潛力的有機太陽能電池材料。

並列關鍵字

Carbon nanotube ； Soar cell ； Light-harvesting polymer

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