The Application and Optical Properties of Organic Material Combined with ZnO Thin Film

• Main Authors: Ming-Shiun Lin, 林明勳
• Other Authors: 林清富
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/ak4xa9

碩士 === 國立臺灣大學 === 光電工程學研究所 === 101 === In our study, we report the application and optical properties of organic material combined with ZnO nanostructure thin film. First of all, we introduce how to obtain the ZnO thin films prepared by sol-gel method and hydrothermally prepared ZnO micro/nanorods. Then we demonstrate a low-temperature process to synthesize ZnO nanorods/polymethylmethacrylate (PMMA) heterostructures with remarkable high defect emission via an all-solution process. Through controlling the appropriate UV/ozone exposure time to induce surface modification on the PMMA, a scanning electron microscope (SEM) shows that high defect emission ZnO nanorods were successfully grown on the surface of the PMMA. A Fourier transform infrared spectra (FTIR) and water contact angle measurement verify that the UV/ozone treatment greatly enhanced the hydrophilicity of the PMMA surface. Room temperature photoluminescence spectra (PL) reveals a very weak band gap emission and extremely intense defect emission. The evaluation based on the peak ratio of defect emission to band edge emission (IDpeak/IBpeak) reveals that the peak of defect emission intensity was 400 times stronger than band edge ultraviolet emission (IDpeak/IBpeak = 400). The temperature-dependent photoluminescence spectra data was well-fit to Arrhenius law and obtained activation energy 77.6 meV. Relatively low activation energy verify that an abundant recombination center existed in our sample. Experimental data show that the interface defect states between PMMA and ZnO are mainly responsible for such a high IDpeak/IBpeak ratio. Subsequently, in order to enhance the blue emission ,we utilized blue organic material-PF(polyfluorene),surfactant and combine ZnO nanoparticles to synthesize PF:ZnO nanoparticles system. From results of FTIR, the function of surfactant is to provide OH groups to make ZnO nanoparticles dissolved in PF instead of influencing The photoluminescence spectra of PF:ZnO nanoparticles can be clearly revealed by two clear emission. One is blue emission wavelength center at 428 nm; the other is yellow-green emission with long tail wavelength center at 532 nm. The blue emission band is attributed to PF. The yellow emission is originated from the interface defect states between PF and ZnO nanoparticles. Subsequently, in order to optimize the weight of doping ZnO nanoparticles in PF:ZnO nanoparticles system, we doped a series of different ZnO nanoparticles in PF:ZnO nanoparticles system. We found that the highest PL EQE(External Quantum Efficiency) 76.06% occurs at the amount of doping ZnO nanoparticles 0.05 g in PF:ZnO nanoparticles system ,which is comparable with commercial YAG:Ce phosphor (EQE is 75%). The range of color temperature is around 3862K~7674K, the white light of PF:ZnO nanoparticles is usually cold-white. The lifetime test of PF:ZnO nanoparticles 0.05g the has exceeded 11 weeks in package with no observable degradation under continuous strong UV LED (370 nm ) exposure. The total of white light integrated PL intensity decrease about 10%. The process we use by an all-solution procedure lowers the total cost of phosphor. The material system we present has high potential to serve as a UV-excited phosphor for white-light applications.