Multimode Luminescence Tailoring in PMA₄Na(In,Sb)Cl₈ Organic–inorganic Hybrid Metal Halide via Rigid Benzene Ring Induced Local Lattice Distortion

Abstract Low dimensional organic‐inorganic hybrid metal halide materials have attracted extensive attention due to their superior optoelectronic properties. However, low photoluminescence quantum yields (PLQYs) caused by parity‐forbidden transition hinder their further application in optoelectronic devices. Herein, a novel yellow‐emitting PMA 4 Na(In,Sb)Cl 8 (C 7 H 10 N + , PMA + ) low‐dimensional OIMHs single crystal with a PLQY as high as 88 % was successfully designed and synthesized, originating from the fact that the doping of Sb 3+ effectively relaxes the parity‐forbidden transition by strong spin‐orbit (SO) coupling and Jahn‐Teller (JT) interaction. The as‐prepared crystal shows an efficient dual emission peaking 495 and 560 nm at low temperature, which are ascribed to different levels of 3 P 1 → 1 S 0 transitions of Sb 3+ in [SbCl 6 ] 3− octahedral caused by JT deformation. Moreover, wide‐range luminescence tailoring from cyan to orange can be achieved through adjusting excitation energy and temperature because of flexible [SbCl 6 ] 3− octahedral in the PNIC lattice. Based on a relative stiff lattice environment, the 560 nm yellow emission under 350 nm light excitation exhibits abnormal anti‐thermal quenching from 8 to 400 K owing to the suppression of non‐radiative transition. The multimode luminescence regulation enriches PMA 4 Na(In,Sb)Cl 8 great potential in the field of optoelectronics such as temperature sensing, low temperature anti‐counterfeiting and WLED applications.