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

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 PMA₄Na(In,Sb)Cl₈ (C₇H₁₀N⁺, 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 Sb³⁺ 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 ³P₁→¹S₀ transitions of Sb³⁺ in [SbCl₆]^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 [SbCl₆]^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 PMA₄Na(In,Sb)Cl₈ great potential in the field of optoelectronics such as temperature sensing, low temperature anti-counterfeiting and WLED applications.