| Summary: | 碩士 === 國立臺灣大學 === 光電工程學研究所 === 97 === In recent years, light emitting device (LED) and organic light emitting device (OLED) are widely studied. Due to the convenience in fabrication, these device are usually made as layered structure, which represents that the lateral size is much larger than the thickness in the emission layer. Generally, there are two kinds of analytical method most popularly used in the simulation of light propagation in these devices. The first one is the finite-difference time-domain method, which allows more flexibility for the simulation structure. However, it consumes vast CPU resource and executing time, and usually be used in the cases when the simulation structure has complicate substructures, i.e. like grating. The second one is the transfer matrix method. In contrast, transfer matrix method requires lesser computation. However, traditional transfer matrix method can only be used in the simulation of layered structure, and suffers difficulty for special simulation structures.
In this thesis, we use the classical electromagnetic theory to analyze and model the optical properties of layered structure. In general, the source of layered structure can be expressed as a periodic resonating dipole source, which can be expanded as plane wave radiating to all directions. Using the transfer matrix method matching the boundary conditions at each junction, the analytical solutions of the electric fields in each layer can be obtained. In addition, we will combine the rigorous couple-wave analysis and traditional transfer matrix method to model the structures with grating. In other word, traditional transfer matrix method only uses the Fresnel''s equations to match the boundary condition of zero order mode. Using rigorous couple-wave analysis or other grating modeling methods, we can furthermore match the boundary conditions of higher modes. As a result, transfer matrix method can calculate the electric field of the high order modes. Furthermore, we can use the obtained electric fields to calculate the extraction efficiency and the far-field pattern of the device. From the simulation results, we found that the extraction efficiency will not always increase when the grating is including in the structure, and the grating period will strongly effect the extraction efficiency and the far-field pattern. A well designed grating can enhance the extraction efficiency and optimize the far-field pattern.
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