Periodic Reporting for period 1 - HEL4CHIROLED (Helical systems for chiral organic light emitting diodes)
Période du rapport: 2020-01-01 au 2021-12-31
Chirality is the property of left-handed and right-handed objects in the 3D space. In Nature, chirality is known to play a major role in biological systems such as in proteins and polysaccharides. In chemistry and materials science, chiral molecular and supramolecular architectures may also provide added values related to their inherent 3D structure and their chirality-related electronic and optical properties.
The principal research goal of HEL4CHIROLED is the preparation of chiral Organic Light-Emitting Diodes (OLEDs) and other related opto-electronic devices based on new small helical molecules, helical π-conjugated oligomers and helical lanthanide complexes.
In this project, we explore new approaches to increase the performances of opto-electronic devices:
– Using the emission of circularly polarized light (CPL) to improve the performance of displays based OLEDs, and to allow additional functionalities in stereoscopic displays.
– Manipulating the spin of electrons by using a chiral molecule, to improve spin effects (Chiral Induced Spin Selectivity, CISS).
The principal research goal of HEL4CHIROLED is the preparation of chiral Organic Light-Emitting Diodes (OLEDs) and other related opto-electronic devices based on new small helical molecules, helical π-conjugated oligomers and helical lanthanide complexes.
In this project, we explore new approaches to increase the performances of opto-electronic devices:
– Using the emission of circularly polarized light (CPL) to improve the performance of displays based OLEDs, and to allow additional functionalities in stereoscopic displays.
– Manipulating the spin of electrons by using a chiral molecule, to improve spin effects (Chiral Induced Spin Selectivity, CISS).
Within the first period, several types of helical molecular scaffolds and chiral lanthanide complexes have been constructed by incorporation of a diversity of chemical functionalities. Their strong chirality enabled to improve absorption and emission of left-handed and right-handed circular light (circular dichroic response and circularly polarized luminescence), in wavelength domains ranging from blue to near-infrared.
- For example, enantiopure helicene-porphyrin conjugates have been prepared. Compared to classical helicene derivatives, they exhibited very intense circular dichroic response and circularly polarized fluorescence in the (far-)red region. This work opens a new field of helically chiral materials for optoelectronic applications.
- Complexes with lanthanides (Ln), notably Ytterbium, Thulium and Erbium complexes were able to induce extraordinary chiroptical properties and give access to discrete energy domains within the NIR region, ranging from 900 to 1600 nm. Indeed, exceptionally high discrimination between left and right circularly polarized light, almost up to the theoretical maximum value, was observed in both absorption and emission for some complexes.
- Some helical supramolecular polymeric systems revealed efficient chirality-induced spin polarization (CISS effect) as evidenced by magnetic conducting atomic force microscopy (mc-AFM). Interestingly, the direction of spin polarization was controlled by the chirality of the environment and the degree of spin polarization was directly correlated to the net helicity. These insights clarify the understanding of the CISS effect being a result of chiral superstructures rather than chiral small molecules. These conclusions open new pathways for the construction of novel organic spintronic devices.
- A biological imaging technique, consisting of a circularly polarized luminescence laser scanning confocal microscopy (CPL-LSCM) capable of simultaneous chiroptical contrast based live-cell imaging of endogenous and engineered CPL-active cellular probes, has been elaborated.
- For example, enantiopure helicene-porphyrin conjugates have been prepared. Compared to classical helicene derivatives, they exhibited very intense circular dichroic response and circularly polarized fluorescence in the (far-)red region. This work opens a new field of helically chiral materials for optoelectronic applications.
- Complexes with lanthanides (Ln), notably Ytterbium, Thulium and Erbium complexes were able to induce extraordinary chiroptical properties and give access to discrete energy domains within the NIR region, ranging from 900 to 1600 nm. Indeed, exceptionally high discrimination between left and right circularly polarized light, almost up to the theoretical maximum value, was observed in both absorption and emission for some complexes.
- Some helical supramolecular polymeric systems revealed efficient chirality-induced spin polarization (CISS effect) as evidenced by magnetic conducting atomic force microscopy (mc-AFM). Interestingly, the direction of spin polarization was controlled by the chirality of the environment and the degree of spin polarization was directly correlated to the net helicity. These insights clarify the understanding of the CISS effect being a result of chiral superstructures rather than chiral small molecules. These conclusions open new pathways for the construction of novel organic spintronic devices.
- A biological imaging technique, consisting of a circularly polarized luminescence laser scanning confocal microscopy (CPL-LSCM) capable of simultaneous chiroptical contrast based live-cell imaging of endogenous and engineered CPL-active cellular probes, has been elaborated.
In the second period, we will apply the knowledge acquired and results obtained on circularly polarized luminescence (CPL) and chirality-induced spin selectivity (CISS effect) to the preparation of chiral Organic Light-Emitting Diodes (OLEDs), Organic Photovoltaics (OPVs), Spin-related devices and Chiral Imaging techniques.
- The generation of novel chiral/helical scaffolds, with improved chiroptical properties compared to the state-of-the-art, will enable to incorporate them into optoelectronic devices. For example, circularly polarized OLEDs (CP-OLEDs) will be fabricated; improved efficiencies, notably in inverted geometries of devices as compared with the more conventional architectures, are expected to be obtained.
- OLEDs will also be fabricated from chiral radicals (species with unpaired electrons). They are expected to display efficient electroluminescence thanks to the inherent properties of the radical species.
- In OPVs, the impact of helical chirality onto charge transport properties will be explored.
- Helicene-based supramolecular polymers or other related chiral systems displaying highly efficient spin-filtering will be incorporated into spin-LEDs. If successful, these results will have a significant impact on the development of spin-based devices.
- CPL-LSCM microscopy technique will be a new imaging tool aiding the development of chiral bio-probes to be taken to the next level. In material sciences, CPL-LSCM could be used for characterising 3D display technologies (e.g. emissive chiral polymers) and verification of CPL-active security inks. Ultimately, it opens a new window into the world of chiral molecular interactions by shedding light onto the previously unexploited chiral biochemical processes that fundamentally underpin life. Such potentialities will be explored.
- The generation of novel chiral/helical scaffolds, with improved chiroptical properties compared to the state-of-the-art, will enable to incorporate them into optoelectronic devices. For example, circularly polarized OLEDs (CP-OLEDs) will be fabricated; improved efficiencies, notably in inverted geometries of devices as compared with the more conventional architectures, are expected to be obtained.
- OLEDs will also be fabricated from chiral radicals (species with unpaired electrons). They are expected to display efficient electroluminescence thanks to the inherent properties of the radical species.
- In OPVs, the impact of helical chirality onto charge transport properties will be explored.
- Helicene-based supramolecular polymers or other related chiral systems displaying highly efficient spin-filtering will be incorporated into spin-LEDs. If successful, these results will have a significant impact on the development of spin-based devices.
- CPL-LSCM microscopy technique will be a new imaging tool aiding the development of chiral bio-probes to be taken to the next level. In material sciences, CPL-LSCM could be used for characterising 3D display technologies (e.g. emissive chiral polymers) and verification of CPL-active security inks. Ultimately, it opens a new window into the world of chiral molecular interactions by shedding light onto the previously unexploited chiral biochemical processes that fundamentally underpin life. Such potentialities will be explored.