Dual-Band Luminescent Lead-Free Antimony Chloride Halides with Near-Unity Photoluminescence Quantum Efficiency

Low-dimensional organic–inorganic
metal halide hybrids (OIMHs)
with an ultrabroad-band emission are promising as downconversion phosphors
for solid-state lighting. However, toxicity of Pb and low photoluminescence
quantum efficiency (PLQE) hamper their application. Herein, two zero-dimensional
(0D) lead-free organic antimony (Sb) chloride (Cl) hybrids with dual-band
emissions and PLQEs: (TTA)2SbCl5 (TTA = tetraethylammonium)
and (TEBA)2SbCl5 (TEBA = benzyltriethylammonium)
are reported. Both compounds show a single broad-band orange emission
with a near-unity PLQE upon low-energy photons (e.g., 360 nm) excitation.
The dual-band emission with an additional blue emission band upon
high-energy photons (e.g., 300 nm) excitation enable (TTA)2SbCl5 to be a single-component phosphor for white light
emission with a PLQE of 68%, correlated color temperature (CCT) of
2360 K and color rendering index (CRI) of 84. Based on photoluminescence
spectra measurements and density functional theory calculations, the
dual-band emission is assigned to the radiative recombination from
both singlet and triplet self-trapped excitons in inorganic [SbCl5]2– pyramids. In addition, both luminescent
compounds exhibit excellent stability against humidity and thermal
attacks. Using (TEBA)2SbCl5 as a yellow downconversion
material, highly stable white-light-emitting diodes with a Commission
Internationale de l’Eclairage (CIE) of (0.36, 0.33), CCT of
4282 K, and CRI of 82 were demonstrated. These results validate that
the title 0D lead-free OIMHs with a dual-band emission and a near-unity
PLQE are promising luminescent materials for solid-state lighting.