| Summary: | 碩士 === 國立成功大學 === 機械工程學系碩博士班 === 95 === In the past, the luminescence efficiency of light emitted devices (LEDs) doesn’t work as expected. By using superlattices can be enhanced the luminescence efficiency of LEDs. The principle thing while producing the superlattices film of active layer of LEDs was molecular beam epitaxy. The disadvantages include high manufacturing cost and targets have to be kept modifying. Furthermore, by using self-assembly technology to produce superlattices thin film it can lower the production costs effectively. This is the way through controlling the potential energy between particles to obtain the superlattices thin film. However, by controlling the defect property of superlattice thin film it can be expected to improve around 25%. This study intends to construct an intact theory and computer simulation method in an attempt to probe into the subject of enhancing the luminescence efficiency based on the development of a self-assembly nanoparticles superlattices film formation theory and a luminescence efficiency estimative model.
First, this research uses microcosmic way to confer the potential while nanoparticles are under the fluid. Then, we use the Langevin equation from Brownian dynamics approach to construct the simulation system to analyze crystal aggregation characteristics of superlattices film via defect factor reduction. Moreover, the simulations were executed through experimental design method. Then, the theoretical model was developed by significant factors. At the same time, by using the luminescence efficiency estimation model, the luminescence efficiency was estimated via calculating the light coupling effect on the superlattice thin film. The results obtained by using the present model were found agree well with experimental data in literature. After that, we can computerize the model using the systematized approach to execute the simulation and to estimate the luminescence efficiency. Finally, we can apply the design procedure which was designed meet the research goal of active layer properties of LEDs to prove the practicability of this research.
The model parameters include the surface charge, Hamaker number, dipole moment and particle concentration. It is found via an experimental design method that system parameters and their interaction are significantly affecting the defect property of superlattice thin film. The average estimation error of the luminescence efficiency is decreased from 27.54% to 7.42% in the same material system, and the average estimation error of the luminescence efficiency is decreased from 34.16% to 5.36% in different systems. Also, through the proposed model of superlattices film luminescence efficiency, plan for improving luminescence efficiency can be obtained as soon as possible under the condition of several different limitary combination of parameters. Through practical examples of the superlattices film, active layer on the electroluminescence devices show that the proposed approach can find the best range of composition and parameter accurately for enhancing luminescence efficiency. It improves the luminescence efficiency from 12.33% to 21.4% at the range setting of system parameters.
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