Theoretical design of critical spin speed and the process window for spin-coated self-assembled monolayers

Abstract

Although spin-coating is widely used for the preparation of SAM films, achieving uniform deposition of the SAM layer remains a pressing challenge due to molecular aggregation and uneven film thickness. This study conducts an in-depth investigation into the uniform deposition process of self-assembled monolayer (SAM) films in organic–inorganic hybrid perovskite solar cells. By combining spin-coating techniques with molecular self-assembly behavior, a physical model was established to analyze the effects of process parameters such as spin speed, solution viscosity, and molecular anchoring rate on the uniformity of SAM films. The results demonstrate that a reasonable spin-coating process can effectively suppress molecular aggregation. By deriving the critical spin speed range, a theoretical framework for optimizing the spin-coating process was proposed, providing practical guidance for improving experimental procedures. Comparison of simulation results with existing literature data validated the model's accuracy and further highlighted the significant roles of centrifugal force and evaporation effects during film formation in the spin-coating process. Based on this model, this study offers new insights for interface engineering optimization in organic–inorganic hybrid solar cells and provides theoretical support for the design and optimization of other functional film systems prepared via spin-coating.