Studies On The Luminescence Properties Of Organic Semiconductor LPPP And Related Problems

Recently, organic semiconductor light emitting has attracted a great deal of attention due to future applications in large area light emitting devices and displays. The applications of organic semiconductor as active layers in light-emitting devices offer several prominent advantages such as high efficiency, high brightness and low cost. Another advantage is that the emitting wavelength can be chemically tailored due to the band gap. The microcavity effect provides the possibility to control the spectral properties of emission and is of considerable interest in the realization of flat panel display devices, which require the emission of blue, green, and red light. In this paper, ladder-type poly(p-phyenylene)(LPPP) thin films were used as the light emitter and hole transporter, while dye pyomethene doped Alq was electron transporter. LPPP thin films were prepared by spin coating from a solution of LPPP in toluene and Alq was formed by vapor deposition. Different configuration devices with LPPP single-layer, LPPP micocavity and LPPP/Alq heterojunction were fabricated. Samples were studied either by EL or PL. With ladder-type ribbon structure, LPPP has thermal and chemical stability. With strong fluorescence LPPP showed a broad PL and EL emission with a maximum at 560nm and was regarded as a white light emitter with a strong blue component, thus allowing tunability over the full visible region. The enhanced light-emitting devices were fabricated. Microcavity effects were observed both in EL and PL. The experimental results showed that color tuning could be achieved simply by adjusting the thickness of LPPP layer. The efficiency was also improved. But there are still several problems concerning the stability and reproducibility of device fabrication. The heavily born doped p-type diamond films synthesized by hot filament chemical vapor deposition with B(CH3)3 as boron source substituted the metal electrode aluminum. With superior properties such as high thermal conductivity, high hole mobility, excellent chemical, thermal and radioactive stability, p-type diamond electrode can also greatly improve the stability of the devices, which complement the current electrode.The effect of boron concentration on the electronic properties of diamond films was investigated by Raman spectroscopy, X-ray photoelectron spectroscopy andscanning electron microscopy. Based on the grain boundary conducting, a model for the calculation of resistivity, mobility and activation energy is presented. Close agreement between experiments and calculation is reached. It was concluded that the model correctly described the doped diamond films conducting, providing a certain extent quantitative analysis.