Inkjet printing is already regarded as a transformative technique for producing organic light-emitting diodes (OLED) due to its low cost, high material utilization, and short procedure. However, the application of printed OLED has been severely limited by the appearance fault of cured microdroplets. The process of microdroplets evaporation is complicated and hard to monitor experimentally since it spans the nano and micro scales. In this work, a hybrid 3D lattice Boltzmann (LB) model coupled with the Langevin equation model is used to study the evaporation and solidification mechanism of microdroplets in the pit. During the microdroplets evaporation process, the nanoparticles (NPs) are primarily affected by the internal field of microdroplets and the falling liquid level. The internal field will bring the NPs inside the microdroplets to the edge of pit, while the falling liquid level causes the NPs to fall vertically. Based on this law, we propose a modified set of boundary conditions to control the evaporation rate. The slower the evaporation rate, the more NPs gather around the edge. The maximum particle uniformity of 68.27 % is achieved with an evaporation coefficient of 0.85. Ultimately, we successfully achieved a uniform and flat morphology of the cured microdroplets by making the microdroplets evaporate at varying speeds. The mechanism of the evaporation and the solidification of microdroplets in pits are revealed, which is of great significance to the application of printed OLED technology.

中文翻译：

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像素坑中微滴蒸发的纳米颗粒动力学和沉积

喷墨印刷因其成本低、材料利用率高、流程短而被认为是生产有机发光二极管（OLED）的革命性技术。然而，印刷OLED的应用因固化微滴的外观缺陷而受到严重限制。微滴蒸发过程复杂且难以通过实验监测，因为它跨越纳米和微米尺度。在这项工作中，采用混合3D晶格玻尔兹曼（LB）模型与朗之万方程模型耦合来研究凹坑中微滴的蒸发和凝固机制。在微滴蒸发过程中，纳米粒子（NPs）主要受到微滴内部场和液面下降的影响。内部场会将微滴内的纳米颗粒带到凹坑的边缘，而下降的液面导致纳米颗粒垂直下落。基于该定律，我们提出了一组修改后的边界条件来控制蒸发速率。蒸发速率越慢，边缘聚集的纳米粒子就越多。蒸发系数为 0.85，颗粒均匀度最大为 68.27%。最终，我们通过使微滴以不同的速度蒸发，成功地实现了固化微滴的均匀且平坦的形态。揭示凹坑中微滴的蒸发和固化机理，对于印刷OLED技术的应用具有重要意义。