Room-Temperature Synthesized Cd-Doped Cs3Cu2I5: Stable and Excitation-Wavelength Dependent Dual-Color Emission for Advanced Anti-Counterfeiting

Graphical Cd-doped Cs 3 Cu 2 I 5 was synthesized by room-temperature grinding. [CuI 4 ] and [CdI 4 ] tetrahedrons act as photoluminescent centers separately, resulting in the emission colour manipulated by not only Cd feeding amount but also excitation wavelength. The as-prepared Cd-doped Cs 3 Cu 2 I 5 was made into anti-counterfeiting ink and printed on paper. The pattern shows different colours when the excitation wavelength increases from 310 nm to 330 nm. With the development of intellectual properties, concern about advanced anti-counterfeiting is accumulating, which conventional single-modal luminescence can no longer satisfy. As one of rapidly developing 0D materials, copper-based perovskite shows great potential to realize multiple luminescent centers for complex emissions. In this work, Cd was doped into Cs 3 Cu 2 I 5 and showed resultant emission at 560 nm which surprisingly showed a red-shifted excitation peak from that of intrinsic self-trapped emission, resulting in excitation-wavelength dependent emission. When the excitation wavelength increased from 290 nm to 330 nm, the emission of Cd-doped Cs 3 Cu 2 I 5 changed from deep blue to cold white and finally yellow. Afterwards, Cd-doped Cs 3 Cu 2 I 5 was mixed with polystyrene to prepare anti-counterfeiting ink for silk-screen printing. Meanwhile, Cd-doped Cs 3 Cu 2 I 5 maintains outstanding stability after doping, no matter under ambient, continuous UV radiation or high-temperature environment. The intensity can be almost totally recovered after heating-and-cooling cycles. This study lays groundwork for future research into multiple luminescent center manipulation in 0D materials.