Preparation of π-Conjugated Polymer Ultrathin Films and their Application to Organic Nanodevices

π-共轭聚合物由于具有多功能的电子和光子性质、结构灵活性和易加工性，在电致发光器件、场效应晶体管和分子电子器件等方面的应用受到了广泛的关注。这些聚合物膜通常通过流延、浸渍、旋涂和喷墨方法形成。然而，难以在分子水平和分子取向上控制膜厚度。在制备有机纳米器件时，需要控制薄膜的厚度。LB技术具有在分子水平上制备具有分子取向和有序性的薄膜的吸引人的特点。然而，π-共轭聚合物由于芳香族主链间强的π-π相互作用，在水表面形成单分子膜的能力较弱，为了克服这一问题，我们尝试制备π-共轭聚合物和两亲聚合物的混合LB膜。我们发现，poly（N-d ...更多信息 十二烷基丙烯酰胺（pDDA）具有在水表面形成稳定的单分子膜并形成优异的LB膜的能力。研究了pDDA与聚3-己基噻吩（PHT）或聚[2-[2 '，5'-双[2“-乙基己氧基]苯基]-1，4-亚苯基乙烯基]（BEHP-PPV）的混合物在水表面的单层行为，并利用叉指阵列（IDA）电极测量了其混合LB膜的电导率。我们发现π-共轭聚合物与pDDA具有良好的互溶性，并且通过LB技术，混合物可以在水表面形成稳定的单分子膜，并在基底上形成LB膜。以pDDA和π共轭聚合物为原料，采用LB法制备了π共轭聚合物导电膜。掺杂后的混合PHT LB膜的电导率为3S/cm，比未掺杂的高出3个数量级。研究了PHT混合LB膜在有机电致发光器件中的空穴注入性能。需要ITO阳极的功函数与空穴注入材料的HOMO能级之间的能量势的匹配，而空穴注入层的厚度不需要作为理想的空穴注入层。由于从ITO阳极到PHT膜的空穴注入能垒降低，使用PHT LB膜的EL器件的起始电压随着层数的增加而降低。在单层PHT LB膜电致发光器件中，量子效率得到了提高。我们证明了混合PHT LB膜可以作为EL器件的空穴注入层。少

π-Conjugated polymers have received much attention for the application to electroluminescent devices, field-effect transistors and molecular electric devices because of their versatile electronic and photonic properties, structural flexibility and easy processability. These polymer films are generally formed by casting, dipping, spin-coating and ink-jet method. However, it is difficult to control film thickness at a molecular level and molecular orientation. It is necessary to control the thickness of ultrathin films for preparation of organic nano-devices. The Langmuir-Blodgett (LB) technique has attractive features to fabricate ultrathin films at a molecular level with molecular orientation and ordering. However, π-conjugated polymers have less ability to form monolayer on a water surface due to strong π-π interaction between aromatic main chains.To overcome the problem, we try to fabricate mixed LB films of π-conjugated polymer and an amphiphilic polymer. We have found that poly(N-d … More odecylacrylamide) (pDDA) has an ability to form a stable monolayer on the water surface and to fabricate an excellent LB film. In this study, the monolayer behavior of the mixtures of pDDA and poly(3-hexylthiophene) (PHT) or poly[2-[2',5'-bis[2''-ethylhexyloxyl]phenyl]-1,4-phenylene vinylenel (BEHP-PPV) on the water surface was investigated and conductivity of their mixed LB films was evaluated by conductivity measurement using interdigitated array (IDA) electrodes. We have found that π-conjugated polymers are well miscible with pDDA and the mixtures can form a stable monolayer on a water surface and LB film on substrates by the LB technique. The π-conjugated polymer ultrathin conducting film was fabricated by LB method using the mixture of pDDA and π-conjugated polymers. The conductivity of the mixed PHT LB film becomes 3 S/cm with doping, which is about three orders of magnitude higher than that of the undoping. It is expected to fabricate molecular electronic devices using the mixed LB films.Performance of the mixed PHT LB films on hole-injection for organic electroluminescent (EL) devices was also investigated. The matching of the energy potential between the work function of the ITO anode and HOMO energy level of the hole-injection materials is needed whereas the thickness of the hole-injection layer would not be needed as an ideal hole-injection layer. Onset voltage of EL devices using PHT LB films decreased with increasing number of layers due to reduction of energy barrier of hole injection from indium-tin-oxide (ITO) anode to PHT films. Quantum efficiency was improved at the monolayer PHT LB film EL devices. We demonstrated that the mixed PHT LB films could function as a hole-injection layer for EL devices. Less