To carry out their activities, Research Teams of the Frédéric Joliot Institute for Life Sciences have developed high-profile technological platforms in many areas : biomedical imaging, structural biology, metabolomics, High-Throughput screening, level 3 microbiological safety laboratory...
All the news of the Institute of life sciences Frédéric Joliot
Scientific result | Chemistry | Technologies
A team from SCBM, in collaboration with IRAMIS, LETI, ENS Paris-Saclay, the Universities of Rennes and San José (USA), has developed new electroluminescent molecules with properties that improve the energy consumption and light production of organic light-emitting diodes (OLEDs). This is the first study correlating the structure and properties of this type of materials, with a promising future in display technologies.
In our OLED (Organic Light-Emitting Diode) screens, the quality of the light produced is greatly diminished by the anti-reflection filters that equip them (Scheme). Indeed, these filters prevent the reflection of external light (sunlight, street lighting) on the OLED slab, but if the device does not emit circularly polarized light (see paragraph below), 50% of the light intensity produced by the diode is lost.
In 2016, work conducted by SCBM researchers (Feuillastre et al, JACS, 2016) led to the development of purely organic electroluminescent materials (without rare metals) which, through their design and structure, exploit three properties that improve their "energy consumed" versus "quality of light produced" performance : i) the emission of Thermally Activated Delayed Fluorescence (TADF), which theoretically makes it possible to transform all electrical energy into light ; ii) the increase of light emission by aggregation or how designed luminophores still gain in efficiency when their concentration is increased and they are arranged in solid material, contrary to classical luminophores which see their efficiency drop at this stage (Figure 1) ; iii) the emission of circularly polarized luminescence (CPL)*, which passes through the anti-reflection filters placed on the screens without attenuating the light produced by the OLED slab, a very rare phenomenon in the organic world.
While classical CPL-emitting fluorophores are intrinsically chiral (high synthesis cost), the concept of "chiral perturbation" makes it possible to confer chiroptic properties to an active chromophore by attaching to it a commercially available chiral unit** that already has the desired spatial geometry (Figure 2). In the present study, researchers have synthesized a series of novel luminophores to perform the first systematic analysis of the structure/properties relationships for this type of organic materials and to understand the parameters influencing the efficiency of the chiral perturbation and thus the obtention of the best properties for these materials. Some of the obtained molecules were then integrated into the first circularly polarized light emitting OLEDs, architecturally designed to fit into high-resolution portable displays.
Optimizing the phenomenon of chiral perturbation was essential so that the teams could continue to work on improving the quality of the light produced and obtain a true OLED material that is revolutionary and exploitable for the industry.
Frédéric L, Desmarchelier A, Plais R, Lavnevich L, Muller G, Villafuerte C, Clavier G, Quesnel E, Racine B, Meunier-Della-Gatta S, Dognon JP, Thuéry P, Crassous J, Favereau L, Pieters G. Maximizing Chiral Perturbation on Thermally Activated Delayed Fluorescence Emitters and Elaboration of the First Top‐Emission Circularly Polarized OLED. Advanced Functional Materials, August 2020, in press
CEA is a French government-funded technological research organisation in four main areas: low-carbon energies, defense and security, information technologies and health technologies. A prominent player in the European Research Area, it is involved in setting up collaborative projects with many partners around the world.