Blue Emission from Charge-Transfer Excitons in Hybrid Organic-Inorganic Quantum Wires: (ABT) [PbCl₃]

Organic-inorganic hybrid (OIH) materials have the potential of providing synergetic properties and promising novel optical properties. This work focuses on the charge-transfer (CT) excitons which play a critical role in a new OIH material, with formula (C₇H₇N₂S) [PbCl₃] abbreviated as ABTPbCl₃. Its crystal structure is built up from edge-sharing [PbCl₆] octahedra, forming one-dimensional infinite double chains surrounded by 2-aminobenzothiazole (ABT) organic molecules. The density of states calculations demonstrate that ABTPbCl₃ has a type-II band alignment, where the valence band and conduction band of the inorganic wires lie upon those of the organic component, respectively. Under UV excitation, the photoluminescence spectrum of ABTPbCl₃ shows a band emission centered at 483 nm. Based on the band alignment, we attribute this bluish emission to CT excitons, which have a lifetime of 5.64 ns. The carrier dynamics is investigated by measuring the luminescence spectra as a function of temperature. At temperature below 210 K, the recombination of carriers is dominated by delocalized excitons, while the mixture of delocalized excitons, electrons, and holes is dominating at higher temperature.