Research on novel organic nano-optical materials operating in invisible wavelength regions

本研究的目的是开发工作在不可见波长区域（如紫外和红外）的有机发光二极管（oled）。研究了有机多薄层和多量子阱（MQW）结构的光学性质。MQW结构由两种有机低分子量材料DCM和TPD组成。我们发现DCM/TPD MQWs中，由于量子尺寸效应，光致发光（PL）光谱中的峰发生波长缩短。在电致发光（EL）光谱中也观察到这种量子尺寸效应。在包络函数近似的情况下，通过数值计算确定了DCM/TPD MQWs中电子的子带能量。由此，我们成功地估计了DCM量子阱中电子的有效质量约为0.5m_0。我们利用在紫外区吸收系数最大的高分子材料PCA制备了聚合物led （PLEDs）。PCA的PL光谱显示出395、510和650 nm三个产峰波长。这表明，如果能在395 nm的辐射部位实现高效载流子注入，就可以制备紫外led。由PCA单层组成的PLED在650 nm处有发光。然而，通过引入空穴传输层，PLED显示出510 nm的光发射。这些结果表明，有机MQW结构可以人为地控制oled的发射波长。此外，我们还发现由掺tpd的PCA有源层组成的led可以有效地控制led的发射波长。

The purpose of this research is to develop organic light-emitting diodes (OLEDs) operating in invisible wavelength regions such as ultraviolet and infrared. We investigated optical properties of organic multiple-thin layers and multiple-quantum well (MQW) structures. The MQW structures consist of two organic low-weight-molecule materials, DCM and TPD. We found that the peak-generating wavelength in photoluminescence (PL) spectra exhibits to be shortened due to quantum size effect in DCM/TPD MQWs. This quantum size effect was also observed in electroluminescence (EL) spectra. The subband energies of electrons in DCM/TPD MQWs are determined by numerical calculation in the context of envelope function approximations. From this, we successfully estimated the effective mass of electrons in DCM QWs as to be about 0.5m_0.We fabricated polymer LEDs (PLEDs) by using a polymer material, PCA, which has the maximum absorption coefficient in the ultraviolet region. A PL spectrum of PCA reveals three peak-generating wavelengths, 395, 510 and 650 nm. This indicates that ultraviolet PLEDs can be fabricated if high-effective carrier injection into the radiative site of 395-nm is realized. The PLED consisting of a PCA single layer exhibits a light emission at 650 nm. However, by introducing a hole-transport layer, the PLED exhibits a light emission at 510 nm.These results indicate that emission wavelengths of OLEDs can be artificially controlled by using organic MQW structures. In addition, we also found PLEDs consisting of a TPD-doped PCA active layer are useful to control the emission wavelength of PLEDs.