Role of Chain Length on (CnH2n+1NH3)2PbX4 (n=6, 8, 10, 12, 14, 16; X=Br and I) 2D Metal Halide Perovskites Physical Properties and Hydrophobicity

We report here the preparation and characterization of two families of RP 2D perovskites including linear monoammonium cations, namely (CnH2n+1NH3)2PbBr4 and (CnH2n+1NH3)2PbI4 with n=4, 6, 8, 10, 12, 14 and 16. Structural and optical properties shows some similarities between the two series of samples with, however, distinct features related to the presence of phase transitions occurring when different ligands are present. Optical properties confirm a general blue-shift for the (CnH2n+1NH3)2PbBr4 system with respect to the CnH2n+1NH3)2PbI4 family with the PL data showing two distinct variation paths for their excitonic emission behavior, one directly related to the chain length and another one depending on the ammonium coordination to the halogen atoms. Water stability of (CnH2n+1NH3)2PbBr4 and (CnH2n+1NH3)2PbI4 has been assessed and the results show an improved hydrophobicity by increasing the number of carbon atoms of the alkyl chain as well as by moving from iodide to bromide perovskites.