Structure distortion-driven optical properties and temperature thermometry in one-dimensional hybrid lead halides.

One-dimensional organic-inorganic hybrid lead halides, (C7H18N)PbX3 and (C13H26N)PbX3 (X = Br, I), were synthesized via a solution method to investigate the correlation between structural distortion and optical properties. All compounds consist of face-sharing PbX6 octahedral chains, where both halide species and organic cations modulate the distortion degree. The iodide compounds exhibit non-centrosymmetric structures and strong second harmonic generation (SHG) responses comparable to KDP, with enhanced SHG intensity correlated to increased octahedral distortion. Temperature-dependent photoluminescence reveals typical self-trapped exciton emission. Notably, (C13H26N)PbI3 shows high thermometric sensitivity (9.1% K-1 at 200 K) with an activation energy of 0.132 eV. This work establishes a clear structure-property relationship linking distortion, excitonic emission, and nonlinear optical response in low-dimensional hybrid halides.