it is really strange for me: spin coatings of MAI on PbI2 takes less than 1 minute according to some papers but dip coating of PbI2 film with MAI needs near 1 hour to have a complete perovskite formation according to some other articles. how is it possible?
One reason is that in spin coating, dynamic forces and agitation improves the mixing process of perovskite precursors and conversion rate...In other words, spinning affects and promotes the kinetics of crystallization.
Well, my understanding is when you mix PbI2 and MAI in DMF - the solvent also takes part in coordination with PbI2 and forms a PbI2-MAI-DMF complex. What you see while spin coating is the solvent is removed which leads to formation and crystallization of perovskite phase. However in the second case, there is only crystalline PbI2 and MAI has to intercalate in this layered PbI2. While the reaction kinetics are also very fast in dip coating, the permeation of MAI becomes more difficult as the perovskite phase growth occurs through surface.
These 2 processes have different kinetics and further also have different physical processes occurring. Hence the difference in crystallization rate. I hope this answers your question.
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