Numerical Simulation on Preparing Uniform and Stable Perovskite Wet Film in Slot-Die Coating Process

Slot-die coatingis regarded as a reliable and potentialtechnologyfor preparing large-area perovskite solar cells with high efficiencyand low cost. Therein, the formation of continuous and uniform wetfilm is of significance to obtain a high-quality solid perovskitefilm. In this work, the rheological properties of the perovskite precursorfluid are analyzed. Then, the ANSYS Fluent is introduced to establishan integrated model of internal and external flow fields during thecoating process. The model is applicable to all perovskite precursorsolutions with near-Newtonian fluids. Based on the theoretical simulationof finite element analysis, the preparation of 0.8 M-FA( x )Cs(1-x )PbI(3), one of the typical large-area perovskite precursor solutions, isexplored. Accordingly, this work indicates that the coupling processparameters like the fluid supply velocity (V (in)) and coating velocity (V) determine theuniformity that the solution flows out of the slit and is coated ontothe substrates, and the coating windows for a uniform and stable perovskitewet film is obtained. For the upper boundary range of the coatingwindows, the maximum value of V and V (in) follows V = 0.003 + 1.46V (in) (V (in) <= 0.1 m/s),while for its lower boundary range, the minimum value of V and V (in) is V = 0.002+ 0.67V (in) (V (in) <= 0.1 m/s). When V (in) is higherthan 0.1 m/s, the film will break due to the excessive V. Finally, the real experiment verifies the accuracy of the numericalsimulation. Hopefully, this work is of reference value for the developmentof the slot-die coating forming process on the perovskite precursorsolution approximating Newtonian fluid.