Lattice Distortion Promoting Wavelength‐Tunable Emissions in Cu(I)‐Based Halides for Thermography and Anti‐Counterfeiting

Low dimensional hybrid metal halides as a chemically tunable platform achieve multi-functional optical applications with versatile luminescence mechanisms. Herein, we design and prepare Cu(I)-based hybrid halide (DMAP)Cu₃I₄ (DMAP = 4-Dimethylaminopyridine), with ambient temperature-induced photoluminescence evolution from red to near-infrared emissions. The in situ variable-temperature crystallographic study reveals lattice distortion with more disordered [Cu_3nI_4n]^n- units appear at high temperature, further indicating that the observed wavelength-tunable emission is attributed to transitions from Cu cluster center to halogen-to-metal charge transfer. Thus, (DMAP)Cu₃I₄ shows a compelling thermometric precision (high sensitivities of 0.0001-0.6 K^-1) at a wide temperature range of 80-300 K. In particular, the remote thermography is established with a high spatial resolution of -20 lp mm^-1 by processable thin films. These findings enhance the potential for molecular-level illumination in Cu(I)-based halides and contribute to the exploration of their optoelectronic properties.