How subtle molecular changes can strongly impact luminescence properties of copper iodide complexes

Copper halides present a wide range of luminescence properties which are relevant for developing sustainable light-emitting materials. A copper iodide complex displaying an unexpected phase transition characterized by a great change of its photoluminescence properties is reported here. Results from different optical and structural characterizations indicate that this contrasted effect involves local defects in the crystalline structure at which the molecular structure is modified. Even minor, these intramolecular changes impact the energetic layout of the complex leading to modifications of the photophysical properties. This study highlights the structural flexibility of the copper halide compounds and the rich panel of stimuli-responsive properties that can result.