Near ultraviolet emission from antimony-based organic-inorganic hybrid halides and their negative temperature coefficient thermistor behavior.

The electrical and optical properties of two zero-dimensional (0D) organic Sb(iii)-based compounds with different coordination configurations, namely (C6H9N2)2[Sb2Cl8] and (C6H9N2)2[SbBr4]Br, were characterized. The negative temperature coefficient (NTC) thermistor parameters of both compounds were characterized based on the important temperature sensitivity coefficient B and resistivity ρ. The B 50/110 value of compound (1) in the temperature range of 50-110 °C was calculated to be 6873 K, whereas the B 90/130 value of compound (2) was calculated to be 15 663 K from 90 to 130 °C, suggesting that both samples are suitable for thermistor applications. The ability to detect small temperature changes is enhanced by a higher sensitivity coefficient B, meaning that compound (2) can be used for high-precision temperature measurement between 90 and 130 °C. The optical properties were characterized by photoluminescence (PL) and photoluminescence excitation (PLE) at room temperature. The results show that the luminescence in (C6H9N2)2[Sb2Cl8] originates from the organic cation, and the [Sb2Cl8]2-dimer exhibits no luminescence under various excitation conditions. Upon 324 nm UV irradiation, this hybrid material shows a strong near ultraviolet (NUV) emission band at 405 nm and a blue shoulder band at 462 nm. The first band is associated with the π-π* transition within the organic molecule, whereas the band at 462 nm is assigned to the organic Frenkel exciton confined in the (C6H9N2)+ cation. For (C6H9N2)2[SbBr4]Br, both theoretical and experimental investigations suggest that the emission involves a resonant energy transfer mechanism in which the organic cation (C6H9N2)+acts as a donor and the inorganic anion [SbBr4]-acts as an acceptor. Accordingly, the broad and intense NUV emission band at 375 nm results from radiative recombination occurring within the organic cation, whereas the bands at 450 and 468 nm are assigned to Wannier and Frenkel excitons, respectively. Our photoluminescence results are supported by WIEN2K calculations of both compounds.