X-ray diffraction, vibrational and photoluminescence studies of the self-organized quantum well crystal H3N(CH2)6NH3PbBr4

We have prepared new semiconductor H3N(CH2)6NH3PbBr4 crystals which are self-assembled organic-inorganic hybrid materials. The grown crystals have been studied by X-ray diffraction, infrared absorption and Raman spectroscopy scattering. We found that the title compound, abbreviated 2C6PbBr4, crystallizes in a two-dimensional (2D) structure with a P21/a space group. In the inorganic semiconductor sub-lattice, the corner sharing PbBr6 octahedra form infinite 2D chains. The organic C6H18N2+ ions form the insulator barriers between the inorganic semiconductor layers. Such a packing leads to a self-assembled multiple quantum well structure. Raman and infrared spectra of the title compound were recorded in the 50-500 and 400-4000 cm−1 frequency regions, respectively. The assignment of the observed Raman lines was performed by comparison with the homologous compounds. Transmission measurements on thin films of 2C6PbBr4, obtained by the spin coating method, revealed a strong absorption peak at 380 nm. Luminescence measurements showed an emission line at 402 nm associated with radiative recombinations of excitons confined within the PbBr6 layers. The electron-hole binding energy is estimated at 180 meV.