Zero-dimensional (0D) hybrid organic-inorganic metal halides with luminescent properties have drawn attention for optical applications like solid-state lighting, X-ray detection, etc. Importantly, it’s been demonstrated that structural isolation of the 0D metal-halide units is crucial for achieving high luminescent efficiencies. Here, we worked on the highly emissive A₂SbCl₅series based on the characteristic SbCl₅ square pyramid. We varied A site cations with different long chains and correlated how their performances change with increasing carbon chain length. In this presentation, we report three novel hybrid compounds [BDTA]₂SbCl₅(BDTA⁺= benzyldimethyltetradecylammonium), [BDHA]₂SbCl₅(BDHA⁺=benzyldimethylhexadecylammonium) and [BDSA]₂SbCl₅(BDSA⁺=benzyldimethylstearylammonium). These compounds are based on quaternary ammonium cations that structurally identical save for having a terminal 14-, 16-, and 18-carbon chain, enabling in-depth analysis of the impact of this chain length on the optical properties_.
All three compounds were synthesized via slow-cooling crystallization in DMF with several drops of HCl. Single crystal X-ray diffraction at low and room temperature reveals that [BDTA]₂SbCl₅and [BDHA]₂SbCl₅are isostructural, crystallizing in a monoclinic crystal system P2₁/c comprising isolated [SbCl₅]^2- square pyramids spaced out by A-cations. Intriguingly, both compounds exhibit bending of the long chain in 50% of the A-site cations, and in [BDTA]₂SbCl₅, this bent portion of the chain exhibits disorder at room temperature which might also have a significant impact on the optical properties. All three compounds exhibit a strong bright orange triplet emission, e.g. [BDTA]₂SbCl₅emits at 620nm for a low energy excitation at 360nm. In addition, it also exhibits singlet emission at around 470nm for high energy excitation at 310nm. This compound [BDTA]₂SbCl₅has a large Stokes shift of 1.44eV and a photoluminescent quantum yield (PLQY) above 90%, making them promising candidates for applications in lighting and scintillation. This presentation will describe the struggle of growing single crystals with long carbon chain materials, present a novel structure type based on these mixed bent and straight chains, and finally relate these structural details to the excellent optical features of these candidate phosphor materials.

Haimanti Majumder

The University of Texas at Dallas

Appearances