Relation between composition ratio and energy gap of n-Nonylamine/PbI₂ composite materials

By n-nonylamine (NA) intercalation into PbI₂, NA/PbI₂ composite materials were synthesized with the molar ratio, n, of NA for PbI₂ of 0∼4. The energy gap was found to change from 2.43eV to 3.20eV by NA intercalation from the transmittance spectra. In particular, it increased rapidly at n = 0∼1. It was also found from the X-ray diffraction measurement that NA's in the van der Waals gaps formed 2-layers for n ≥ 1, and lay tilted at angles of 53.8° or 30.1° to the c-axis direction. The increase in the energy gap is thus supposed to be caused by the increase of the volume ratio of the 2-layers for the 0-layer.