High External Quantum Efficiency and Dual-Band Emission of (C₇H₁₈N)₃Sb₂Cl₉ for Sensitivity Temperature Sensing

Organic-inorganic hybrid halides have gained attention for their ease of processing and remarkable optoelectronic properties. However, the relationship between the structure and optical properties requires further exploration. In this study, the butyltrimethylammonium cation (C₇H₁₈N⁺) was chosen, and seven compounds were synthesized: (C₇H₁₈N)₃Sb₂X₉ (X = Cl, Br), (C₇H₁₈N)₃Bi₂X₉ (X = Cl, Br, I), and (C₇H₁₈N)(C₂H₈N)MBr₅ (M = Sb, Bi). Crystals with a single organic cation exhibit a zero-dimensional structure, while the introduction of dimethylamine ions increases the crystal dimensionality from zero-dimensional (C₇H₁₈N)₃Sb₂Br₉ to one-dimensional (C₇H₁₈N)(C₂H₈N)SbBr₅. Under 372 nm excitation, (C₇H₁₈N)₃Sb₂Cl₉ showed broad orange-red single-band emission with a high photoluminescence quantum yield of 88.4% and an external quantum efficiency of up to 56.9%. A white light-emitting diode based on (C₇H₁₈N)₃Sb₂Cl₉ achieved a high color rendering index of 96.3. Moreover, dual-band emission was observed in (C₇H₁₈N)₃Sb₂Cl₉ under 308 nm excitation, which exhibits an absolute temperature sensitivity of 1.96 × 10^-3 K^-1 (320 K), and a flexible film was prepared by incorporating polydimethylsiloxane. This shows the promise of hybrid metal halides as photoluminescent materials and their possibilities for temperature sensing.