Research Of Roll-to-roll Coating Equipment For Flexible Organic Photovoltaic Devices

Roll-to-roll manufacture of large-area and high-efficiency flexible thin-film photovoltaic devices is one of the research directions of the photovoltaic industry in recent years.Organic photovoltaic cells(OPV)appears frequently in the studies of the production of thin-film photovoltaic device due to that its raw materials are numerous and can be made into liquid.In these studies roll-to-roll coating and printing process has been tried many times,but the results are not satisfactory.The main difficulty is that the coating quality decline,the photoelectric conversion efficiency is greatly reduced and the service life is not long enough when the area of the photovoltaic device is increased.This is caused by many factors,one of the reasons is the lack of roll-to-roll coating and printing equipment for photovoltaic devices.Although the roll-to-roll process has a long history,the traditional roll-to-roll equipment can not be used directly to the production of large area photovoltaic devices because of the different processes,because the quality of the coating can not be guaranteed.Therefore,the technological requirements and process flow of OPV are studied in this paper.And a simple roll-to-roll coating equipment for OPV active layer is designed.The main contents are as follows:(1)Firstly,slot-die coating technology is chosen to make the coating according to the technological requirements of the OPV active layer.Then the mathematical model of the coating process is set up,and the design guidelines of the slot-die coating nozzle are studied.Further more,the general composition of the roll-to-roll coating process is studied and the overall scheme of the equipment is determined(2)Secondly,the operation parameters of the equipment are determined according to the technological requirements.Based on that,the structure of the slot-die coating nozzle,coating platform,unwinding and rewinding mechanism and hot air drying oven are designed,and the design of the whole equipment is carried out.Then through the computational fluid dynamics(CFD)technology,the simulation analysis of the flow field of the coating nozzle and the air duct of the oven is carried out,the size of the coating to ensure the coating uniformity in the width direction is determined,and the uniformity of the air velocity and temperature at the outlet of the drying oven is proved to be able to meet the requirements.In addition,the relationship between the coating interval,the coating speed and the minimum wet film thickness is studied.It is found that the small coating thickness could be gain only when the coating speed is high.(3)Thirdly,the tension model of the roll-to-roll equipment is set up,and the influence of manufacturing and installation error of the roller on tension and speed is analyzed.According to the tension model,PID controller and linear quadratic regulatory(LQR)are designed for tension and speed closed loop control respectively,and the performance of the controller is analyzed by matlab simulation.It is found that when the PID controller is used in the speed control,and the LQR is used in the tension control,the system gains best response.(4)Finally,the electrical scheme of the system is determined according to the characteristics of the control equipments,the selection of the devices and the detailed design of the electrical circuit are carried out,the PLC program and the human-computer interface are coded according to the control process.Then,a simple roll-to-roll test platform is built,the functions of the PLC program and the human-computer interface are verified.