Enhancing uniformity in large-area slot die coating of low-viscosity perovskite ink

Large-scale slot die coating technology is crucial for producing perovskite films in perovskite solar cells. Producing high-quality perovskite films requires a stable coating window to ensure that the thickness of the films is uniform and free of defects. This research delves into the production of high-quality perovskite films via slot die coating. It employs a combined approach of theoretical analysis and numerical simulation to define coating limits. Furthermore, it examines the influence of the geometric structure within the internal flow field and the transformation of fluid flow patterns in the external flow field on the overall film quality. We demonstrate that the removal of the edge geometry to the transverse fluid channel in the coating head significantly improves the stability of the internal flow field and enhances the consistency of fluid discharge. Additionally, uniform and stable coating of a perovskite solution can be achieved when the speed of the coating substrate in the downstream coating gap exceeds 0.7 times the maximum velocity of the Poiseuille component of the flow, and the coating flow pattern in the downstream coating gap remains consistent with Couette flow.