OLED consists of a thin layer of anode – typically indium-tin oxide, ITO, -upon the plastic or glass substrate, and a number of organic layers, the main of them being the Light Emitting Layer, covered by a thin film of metal cathode. The whole thickness of this heterostructure is only about 100-200 nm!sThe advantages
What is the problem
As OLEDs meet the mass market, the price of the device becomes of crucial importance. Nevertheless, though in principal OLED technology offers very cheap production, currently OLED devices are very expensive. One of the reasons is extremely high cost of the emitting materials.
Instead of using expensive iridium compounds, we offer to use cheap lanthanide complexes.
EVOLED LCC has found the new approach to create emissive layer based on lanthanide aromatic carboxylates. Our method has no analogues on the market. By using a unique expertise of our scholars, we have found a way to deposit highly emissive and stable lanthanide aromatic carboxylates thin films and made the impossible possible.
We optimized this chemical approach to deposit thin films of desired composition with appropriate characteristics as pure as within a host material.
The purposeful selection of ligands L has allowed us to deposit thin films of lanthanide derivatives of mono and di-carbonic acids with controlled thickness of 40-200 nm and roughness <4% of thickness.
Lanthanide aromatic carboxylates typically form coordination polymers due to very large lanthanide coordination numbers together with low denticity of the carboxylate ligands. It makes them insoluble and non-volatile – unlike their mixed-ligand complexes, in which coordination sphere is saturated thanks to additional ligands.
As soon as we find an additional ligand that can not only attach to the lanthanide aromatic carboxylate, but be also easily removed at heating, we can use a MLCFD method:
— deposit a thin film of a mixed-ligand complex from a solution
— and heat it up to the additional ligand elimination, but not too high in order not to destroy the aromatic carboxylate itself.
We have found such mixed-ligand complexes, suitable to obtain thin films emitting in both green and red with high quantum yields. You can find the detailed information in our papers and patents.