Research On Computer Simulation And Visualization Of Growth Mechanism Of High-Efficiency Solar Cell

Energy and enviromment are two principal problems people confront in the 21st century. The world energy which used to be mainly petrochemical energy will gradually convert into renewable resources - solar energy. Solar energy is inexhausted and pollution-free. At present, high-efficiency multijunction tandem solar cells (GaAs basic series multijunction solar cells) are the most competitive in the new generation solar cells in the world, and are high-performance and long-life space main electrical sources which aerospace craft urgently requires. Among the development methods of GaAs tandem solar cells, metal organic chemical vapor deposition (MOCVD) is optimum. Nowadays all the studies at home and abroad have been paid attention to technical characteristics of GaInP/GaAs/Ge tandem solar cells from the experimental aspect, consequently optimizing processing and structural parameters, but the dynamic mechanism of GaInP film growth has little attention from the point of view of computer simulation.However, computer simulation has usually more advantageous at aspects of model building and computing analysis, being short of intuitive and interactive characteristics. Virtual reality (VR) visualization technology has made up the disadvantages of computer simulation, and can help designer and technician find the problems of design, consequently providing theoretical basis for improving design. Therefore, the organic combination of computer simulation and VR visualization technology can create a more humanized integrated simulation system, providing guidance basis for the optimization of structural design and processing parameters.With the background of high-efficiency mulitjunction solar cell made by MOCVD equipment, this thesis uses the study method of combining computer simulation with visualization, studying growth dynamic mechanism of GaInP epitaxial material from the macroscopic level and microscopic level respectively. The thesis's main study contents and results are as follows:1. Method of Computational Fluid Dynamics (CFD) was applied to numerical simulation of gas's thermal and flow fields of MOCVD reactor which grows high-efficiency three-junction GaInP/GaAs/Ge tandem solar cells. Through CFD numerical simulation of gas's thermal and flow fields in reactor for different processing parameters, the results are acquired that, on a certain conditions, the distributions of thermal and flow fields over the substrate are relatively uniform at the total gas flux of 5L /min and system pressure of 0.1atm. Meanwhile, the substrate length must be not more than the distance between two ends of exhaust gas, thus providing rational suggestion for optimization design in size of the substrate in the reactor. 2. VR visualization technology was applied to the visualization of gas's thermal and flow fields of MOCVD reactor. The visualization results truly and intuitively display distributing situation of gas's temperature field and velocity field in MOCVD reactor. Researches can visually see the distributions of temperature and velocity fields inside reactor through wall, thus adjusting the processing parameters such as the heater's temperature and the whole flow of gas's inlet in time so as to acquire uniform thermal and flow fields over Ge substrate.3. Orthogonal experimental method was applied to numerical simulation experiment for processing parameters of GaInP thin film cell grown by MOCVD. With range analysis and variance analysis on experiments, the importance order of processing parameters affecting thickness of the flat-temperature zone is found, and the best level combinations of parameters are confirmed. Meanwhile, non-linear regression analysis is used to build mathematical models of processing parameters based on thickness of the flat-temperature zone. By means of the experimental verification, the universality of processing parameters'effect on thickness of the flat-temperature zone is verified, and experiential formula is offered for thickness of the flat-temperature zone of thermal and flow fields of MOCVD. All those provide theoretical basis for reasonably confirming processing parameters of MOCVD.4. With the object of growing high-efficiency multijunction tandem solar cells by MOCVD technology, this paper proposed a model and algorithm of multielement compound GaInP thin film growth based on method of Kinetic Monte Carlo (KMC). KMC simulation was carried out for GaInP thin film growth process.5. The result of KMC simulation was combined with VR visualization technology. The visualization emulation of the process of GaInP thin film growth in MOCVD reactor was realized. The results of simulation and visualization truly and intuitively display process of GaInP thin film growth in MOCVD reactor, and they reveal the rule of influence of simulation time, substrate temperature and deposition rate on GaInP thin film morphology. The simulation results well coincide with experimental results, providing the optimizations of processing parameters of GaInP thin film grown by MOCVD with theoretical basis.6. Based on Visual Studio.net2003 and Open Inventor, a prototype system of simulation of growth mechanism of high-efficiency solar cell was implemented in the environments of Microsoft Windows. All modules in the system design are realized in the prototype system.By the study of this paper, the processing parameters of high-quality GaInP thin film material are acquired under a certain conditions. The study is of important meaning for improving the efficiency and quality of solar cell.