In-situ investigation of organic devices by using infrared spectroscopy and photoelectron analysis

在这项研究中，我们用光谱和电测量相结合的方法对有机器件进行了研究。前者采用多反射几何中的红外反射吸收光谱（MIR-IRAS）和光电产率光谱（PYS），后者采用位移电流测量（DCM）。我们已经将DCM技术应用于各种有机器件，如有机晶体管、有机电致发光器件和有机双稳态器件。然后我们发现，该技术可以为我们提供有关载流子在有机器件中的行为的有用信息，如载流子注入、积累、陷阱数量和累积电荷的空间分布。对于有机晶体管，我们发现在可见光照射下，有机半导体中的杂质掺杂得到增强，并提出了一种新的掺杂方法“光致掺杂”。对并五苯和多噻吩薄膜的MIR-IRAS测量揭示了光诱导掺杂的机制是通过光诱导电荷转移加速宿主有机半导体和客体杂质掺杂之间的电荷转移。我们研制了一种可以在真空和大气条件下测量光电子产率谱的仪器。由于氮净化紫外单色光源的内部，广泛的光子能量（4-9eV）可用于覆盖大多数有机材料。我们还证明了PYS技术可以用于分析有机/金属界面的电子结构。在我们的建议下，最近，一家日本公司开发了一种用于测量OLED材料电离势的商用仪器。

In this study, we have investigated organic devices by combing spectroscopic methods and electric measurement. As the former, infrared reflection absorption spectroscopy in the multiple reflection geometry (MIR-IRAS) and photoelelctron yield spectroscopy (PYS) were applied, and as the latter, displacement current measurement (DCM) was used.We have applied DCM technique to various organic devices such as organic transistor, organic electroluminescent devices, and organic bistable devices. Then we found that this technique can give us useful information about the behavior of carrier in organic devices such as carrier injection, accumulation, amount of traps, and spatial distribution of accumulated charge. Concerning organic transisotr, we found that impurity doping to organic semiconductor is enhanced by visible light illumination and proposed a new doping method of "photoinduced doping". MIR-IRAS measurement of pentacene and polythiophene film revealed that the mechanism of the photoinduced doping is the acceleration of charge transfer between host organic semiconductor and guest impurity dopant through photoinduced charge transfer.We developed an apparatus with which photoelectron yield spectroscopy can be measured both in vacuum and atmospheric conditions. Due to purging the inside of a UV monochromatic light source by nitrogen, a wide range of photon energy (4-9eV) is available to cover most organic materials. We also demonstrated that PYS technique can be used to analyze electronic structures of organic/metal interface. Under our advice, very recently, a commercial apparatus for measuring ionization potential of OLED materials have been developed by a Japanese company.