Study of Photorefractive Dynamics in Poly(triarylamine)-based Polymer Composites

The Photorefractive (PR) effect is defined as spatial modulation of the index of refraction due to charge redistribution in a nonlinear optical material. Holographic displays using the PR effect have received a great deal of attention because they can provide 3D images without special eyeglasses. For practical use of the PR materials, high external diffraction efficiency and fast response are indispensable. This thesis consists of six chapters. The PR dynamics in poly(triarylamine) (PTAA) based polymer composite was discussed from chapter 3 to chapter 5. In this study, PTAA was chosen as a PR photoconductive polymer, expected to lead fast response due to its high hole mobility.In chapter 3, the diffraction efficiency as a function of applied field demonstrated appropriate applied field region of 45-60 V μm-1. Wavelength dependency of the PR performance was examined. The shorter wavelength illumination induced higher diffraction efficiency and faster response time due to appropriate charge generation. In chapter 4, the PR dynamics of PTAA-based composite with small amount of a second electron acceptor was investigated. The second electron trap agents reduced photocurrent and suppressed the dielectric breakdown. The addition of bathophenanthroline (BPhen) provided high PR performance with response time of 397 μs, external diffraction efficiency of 5.9% and sensitivity of 1145 cm2 J-1. The effect of photoconductivity on the PR response time is discussed.In chapter 5, the composition ratio of PTAA-based composite was optimized to obtain the enhanced PR performance. The resulting composite achieved higher external diffraction efficiency of 23.9% and higher sensitivity of 1851 cm2 J-1. The key point of the optimization of the composite is the control of the absorption coefficient, related to the external diffraction efficiency. The extremely high sensitivity, as an indicator of the performance of real-time 3D holographic displays containing the elements of the response time and the external diffraction efficiency, indicated the PTAA-based PR composite as the most promising candidate of the holographic displays.