For the measurements, films of about 500 nm have been prepared on quartz substrate through spin-coating method (see Experimental Section). For the (CnH2n+1NH3)2PbI4 series, the starting value of the contact angle is roughly around 60°, without relevant differences as a function of n. For n=6 and 10, the angle value rapidly drops within the first seconds of the measurements and after about 20 seconds the measurement is not reliable anymore. On the opposite, for n=16, after an initial slight reduction of the angle, the value remains constant around 50°. This result confirms the evidence of a high hydrophobicity for the (C16H33NH3)2PbI4 composition as reported recently in ref. 13 where the perovskite has been used in photocatalytic applications. For the (CnH2n+1NH3)2PbBr4 series the starting values of the contact angles are higher with respect to the iodide analogues (cfr.