Thermochromic photoluminescent 3D printed polymeric devices based on copper-iodide clusters

In this work, optically active devices are fabricated by Digital Light Processing (DLP) 3D printing technology employing copper-iodide photoluminescent clusters as smart dyes in the photocurable formulation. These compounds are easy to synthesize, low cost and possess large stoke shift, thermochromic and rigidochromic properties, which make them particularly appealing for the development of optical devices. By dispersing such compounds in photocurable formulations, the same properties are transferred to polymeric materials, enabling the production of a large range of devices. Absorbing in the UV range and emitting in the visible range, those clusters show twofold advantages: on the one hand, competing with the photoinitiator for the light absorption, they allow a better control of the photopolymerization process, enabling the fabrication of precise structures; on the other hand, these possess aesthetic properties, being transparent and then emitting light when irradiated. At last, functional structures, such as 3D printed polymeric waveguides (PWGs) and downshifting devices, are fabricated and investigated but even other uses can be envisaged, such as cryogenic optical thermometers.