Structural dynamics and multifunctionality of zero-dimensional Sb-based halides: Unveiling anomalous thermal quenching and pressure-driven luminescence control

Zero-dimensional lead-free metal halides have emerged as promising alternatives for optoelectronic applications, yet their thermal quenching behavior and limited spectral tunability remain challenging. Herein, a zero-dimensional (0D) antimony-based halide is reported, (C₁₂H₂₈N)₂SbCl₅, exhibiting anomalous negative thermal quenching (NTQ) and pressure-driven multicolor cycling. The crystal demonstrates near-unity photoluminescence (PL) quantum yield at room temperature and exceptional thermal stability to 518 K. Remarkably, an NTQ effect (80–250 K) arises from thermally activated defect to self-trapped exciton (STE) energy transfer, countering nonradiative losses. Under high pressure, in situ photoluminescence reveals reversible emission color cycling and a 200 % intensity enhancement at 3.2 GPa, attributed to [SbCl₅]^2- pyramidal distortion, bandgap narrowing, and selective STE state modulating. Density functional theory calculations confirm that lattice compression shorten Sb-Cl bonds, reduces electron-phonon coupling, and stabilizes metastable STEs. Practical applications are demonstrated in high-resolution latent fingerprint imaging under UV light and as stable plant-growth LEDs, where the emission spectrum optimally matches chlorophyll absorption. This work provides fundamental insights into defect-mediated STE dynamics and establishes a dual-stimuli-responsive platform for tunable luminescence in optoelectronics and imaging technologies.