In the case of the paper, it is said that when the ratio of DMSO to DMF increases, the thickness decreases significantly, and experimentally I feels that way.

Can you explain why? And if the concentration of DMSO needs to be high due to the solubility problem of the precusor, is there a way to increase the thickness of the perovskite film after spin-coating other than increasing the concentration of the precusor?

(The hot casting method is not very reproducible, so it's hard to use)

DOI: 10.1039/c8ta09859j(Low-temperature-processed inorganic perovskite solar cells via solvent engineering with enhanced mass transport)