Dual-Mode Optical Thermometry and Plant-Growth Lighting Enabled by Sb³⁺-Doped Organic-Metal Halide Thin Films

The integration of optical environmental sensing with plant photophysiological regulation into a single-material platform remains a key challenge for smart agriculture. Here, we report a flexible luminescent composite film based on Sb³⁺-doped (C₁₈H₁₅S)₂InCl₅ in a polydimethylsiloxane matrix, which combines optical thermometry and tailored plant-growth lighting. Multidimensional analyses using Raman spectroscopy and steady-state/time-resolved photoluminescence (PL) elucidate the key role of electron-phonon coupling in energy-level modulation and radiative transitions. The emission shows strong excitation-wavelength dependence. Under 360 nm excitation, the film exhibits a pronounced thermochromic shift from red (80 K) to yellow (480 K), enabling temperature readout through emission-peak shifts with a maximum relative sensitivity (S_r) of 0.72% K⁻¹ and supporting visual temperature monitoring for cold-chain logistics. Under 320 nm excitation, simultaneously activated singlet and triplet dual emissions generate a self-calibrated ratiometric optical thermometer with a maximum S_r of 3.92% K⁻¹. Benefiting from its high PL quantum yield and broadband emission matching chlorophyll absorption, orange-red and white LEDs are fabricated. Plant-cultivation tests on gotu kola, garlic sprouts, and Chinese-cabbage seedlings show enhanced growth and chlorophyll accumulation under these tailored light sources. The material presents a flexible optical material that integrates temperature sensing, self-calibrated thermometry, and plant-growth photoregulation, providing a materials strategy for smart agriculture.