Numerical Experiment Using Direct Simulation Monte Carlo for Improving Material Deposition Uniformity During OLED Manufacturing

Numerical experiments to improve the deposition uniformity in organic light-emitting diode (OLED) manufacturing process using direct simulation Monte Carlo (DSMC) technique running on general-purpose graphical processing unit (GPGPU) architecture were conducted in this study. Two ways to improve the deposition uniformity are proposed: one is to select a combination of different nozzle cap diameters, thereby controlling the amount and distribution of evaporated organic material, and the other is to investigate the effect of installing two inner plates on the change in the deposition uniformity associated with the transport of organic material within the crucible. For this purpose, some rules must be followed, namely, different diameters of nozzle caps, e.g., 8, 9 and 10 mm, must be used, and eight nozzles at both edges of the nozzle array must have a diameter of 10 mm. DSMC simulations were performed for all cases with new sets of nozzle array by replacing the initially installed 10 mm diameter caps with 8 or 9 mm diameters caps sequentially. From DSMC calculations of the corresponding deposition uniformity values, it was found that 8 mm diameter caps are more effective than 9 mm diameter caps in producing a good quality of deposition on the glass panel, and the final combination of nozzle caps that satisfies the target uniformity value of less than 2% is finally obtained. On removing the inner plate located immediately below the nozzle array, the deposition uniformity became considerably worse, clearly indicating that the control of the evaporated material transport influences the whole quality of the deposition thickness on the glass panel. It is thus verified that the amount of ejected material through nozzles that are located at the center of nozzle array, and the type of inner plate located below the nozzle, must be precisely determined for manufacturing high-quality OLED glass panels. This study specifically presents the process and possibility of a scientific simulation of DSMC dealing with the behavior of rarefied gases to achieve the optimized goal of a high quality of deposition uniformity in the practical manufacturing process.