Typically, numerous WHLEDs feature excellent color rendering index (CRI >80), color correlated temperature (CCT > 5500K for a cold white, and < 5500K for a warm white), and x/y Commission Internationale de l’Eclairage (CIE) coordinates around 0.33/0.33. Yet, their stability strongly depends on the phosphor. Another important parameter is the photoluminescence quantum yield (PLQY).
In the context of solution statement and strategy, CuMOF-LED proposes to develop a new family of white hybrid OPs based on the combination of bluish green emissive copper complexes embedded into yellowish orange emissive and sustainable metal organic framework (MOFs). MOFs are a class of porous crystalline materials and are here useful for two reasons: i) their porosity is used for copper-based materials encapsulation, providing more stabilization, ii) and they provide a color contribution, necessary for achieving the white emission. This final system is called host-guest hybrid material and leads to white hybrid LED (WHLED), in which hosts are the MOFs and guests are the copper complex This concept is important for our society since it would reduce drastically the ecological impact of LED fabrication, as stated by EU action line.
The MOFs are based on an organic moiety, called ligand, and a metallic node. The latter is, for sustainable and cost purposes, zinc, zirconium, aluminum, or magnesium. The syntheses, purifications, characterizations and photophysical properties of hosts (MOFs) and guests (Cu(I)) complexes and organic emitters were timely achieved. However, the implementation of host-guest systems based on Cu(I) was not successful, despite numerous trials. This was related to i) the guest is too big to enter the hosts’ pore size; and/or ii) the guests are too instable and get oxidized/degraded before entering the hosts’ pore size. Therefore, Cu(I) complexes were replaced by organic dyes, since they are smaller and more stable in solution. In this regard, white emissive hybrid materials, and consequently WHLEDs, were successfully achieved. In a sociological point view, this project goes beyond the state-of-the-art in a sustainable approach.
