高分子及二氧化鈦奈米晶體混成材料中載子遷移率之特性研究

本研究主要是藉由量測P3HT及二氧化鈦奈米晶體混成材料中的電學性質來觀察載子在其中的傳輸機制。首先，我們藉由改變二氧化鈦的晶體大小及混掺濃度來改變混成系統中材料的排列特性，並用渡越時間方法(Time of Flight)分別量測電洞及電子的載子傳輸率，實驗結果顯示不僅載子遷移率有很大的提升，載子也從散佈性的傳輸行為(dispersive transport)轉變為非散佈性的傳導(non-dispersive transport)。其次，我們也使用化學方法對二氧化鈦奈米柱的表面進行改質，並使用渡越時間法觀察不同表面型態對於載子傳導的影響。除此之外，我們也利用新架設的CELIV（Charge Extraction Linear Increasing Voltage）來探討P3HT及二氧化鈦奈米晶體混成材料中的雙載子遷移率(Bi-polar mobility)，實驗結果顯示出與渡越時間法有相當的關聯及一致性。

關鍵字

3-己烷基噻吩；二氧化鈦；載子遷移率；異質接面結構

並列摘要

Hybrid organic-inorganic materials have emerged as a novel class of optoelectronic media for photovoltaic applications. The conversion efficiency can reach up to 5% so far based on P3HT-PCBM bulk heterojunction structure. Even though the bulkheterojunction structure has greatly increased donor/acceptor interfaces and thus facilitates charge separation, both polymer matrix and nanocrystal are forced to form isolated island-like structure which is not favorable for carrier transport. Since carrier transport in amorphous system is mainly through hopping between polymer chain segment and nanocrystals, a continuous conducting path must be required to ensure efficient hopping transport. In this research, we study both hole and electron transport properties in organic-inorganic hybrid system consisting of P3HT and TiO2 nanocrystals. In the first part, the conventional time-of-flight technique is applied to study carrier transport property of both P3HT-TiO2 nanorods and nanoparticles hybrid systems. With the blending of different concentration TiO2 nanocrystals, not only the transient curves become less dispersive but the mobility also shows nearly an order of magnitude increase at most for both TiO2 nanorods and nanoparticles hybrid systems. Moreover, percolation limit is also observed with the increasing of TiO2 concentration coincides with the formation of conducting paths. To further improve the charge transfer efficiency and sunlight harvesting yield, we modify our TiO2 nanocrystals with N3, Cu-Pc, ACA (Anthracene – 9 – carboxylic acid) and also find about an order of magnitude increase in carrier mobility. In the second part of our research, we setup charge extraction linear increasing voltage (CELIV) technique to measure carrier mobility contributed from intrinsic carriers. Experiments show similar results for both the increase of carrier mobility and the saturation of mobility at high blending concentration.

並列關鍵字

P3HT ； TiO2 ； carrier mobility ； bulkheterojunction structure

參考文獻

[34] Muhammad Sahimi, “Application to Percolation Theory”, 1994

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高分子及二氧化鈦奈米晶體混成材料中載子遷移率之特性研究

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