Abstract The development of low‐cost and earth‐abundant phosphors for substituting expensive noble metals and toxic lead materials is currently of major importance for sustainable solid‐state lighting technologies. Hybrid copper halide materials are currently receiving considerable attention due to their unique and diverse structural and photophysical properties combined to their low cost and toxicity. This article reports the rational design of copper iodide compounds for developing single‐component white light emitters. By a ligand engineering strategy, the energy layout of the molecular clusters can be adjusted and the variation in the relative intensity of two emission bands can be obtained, enabling white light to be emitted. Temperature dependence of this dual‐emission feature also allows high contrast luminescence thermochromism. Thanks to their good solubility properties, the studied copper iodide clusters have been successfully incorporated within organic polymer leading to polymer materials with processability suitable for application development. Therefore, the potential applicability of these composite materials has been demonstrated in various fields as luminescence ratiometric thermometry, single‐component emitters for phosphor‐converted white‐light emitting diodes, and as ink for anticounterfeiting properties. This study highlights the power of the ligand design strategy to develop high potential multifunctional materials based on light‐emitting copper materials.