Photoexcitation dynamics and energy engineering in supramolecular doping of organic conjugated molecules

Triphenylamine Spirofunctionalized Light-Emitting Conjugated Polymer with an Ultradeep-Blue Narrowband Emission for Large-Area Printed Display

Emerging printed large-area polymer light-emitting diodes (PLEDs) are essential for manufacturing flat-panel displays and solid lighting devices. However, it is challenging to obtain large-area and stable ultradeep-blue PLEDs because of the lack of light-emitting conjugated polymers (LCPs) with robust deep-blue emissions, excellent morphological stabilities, and high charging abilities. Here, a novel unsymmetrically substituted polydiarylfluorene (POPSAF) is obtained with stable narrowband emission for large-area printed displays via triphenylamine (TPA) spirofunctionalization of LCPs. POPSAF films show narrowband and stable ultradeep-blue emission with a full width at half maximum (FWHM) of 36 nm, associated with their intrachain excitonic behavior without obvious polaron formation. Compared to controlled poly[4-(octyloxy)-9,9-diphenylfluoren-2,7-diyl]-co-[5-(octyloxy)-9,9-diphenylfluoren-2,7-diyl] (PODPF), excellent charge transport is observed in the POPSAF films because of the intrinsic hole transport ability of the TPA units. Large-area PLEDs are fabricated via blade-coating with an emission area of 9 cm2, which exhibit uniform ultradeep-blue emission with an FWHM of 36 nm and corresponding Commission internationale de l'éclairage (CIE) coordinates of (0.155, 0.072). These findings are attributed to the synergistic effects of robust emission, stable morphology, and printing capacity. Finally, preliminary printed passive matrix (PM) PLED displays with 20 × 20 pixels monochromes are fabricated, confirmed the effectiveness of spirofunctionalization in optoelectronics.

Ultraviolet Organic Laser from Rhombus Microcrystal: Benefits of Single-Molecule Emission from Twisted Structure

Light-emitting molecular crystals with efficient emission behavior are crucial for fabricating low-threshold ultraviolet organic lasers. Herein, we demonstrated a rhombus microcrystal from a fluorene-based conjugated molecule (CL-1) with robust emission behavior for an ultraviolet organic laser. Due to the synergistic effect of twisted intramolecular conformation and weak π-interaction, the CL-1 single crystal showed an extremely high photoluminescence quantum yield (PLQY) of ∼82%, due to their single-molecule excitonic behavior. Considering the diverse noncovalent interactions, CL-1 molecules easily self-assembled into the rhombus microcrystals. Finally, a low-threshold ultraviolet organic laser was fabricated with a sharp emission at 379 nm, attributed to the 0-1 vibration band of a single CL-1 molecule, also further confirming the single twisted-molecule emission in crystal states. Precisely controlling the intramolecular twisted structure and intermolecular interaction of organic conjugated molecules is a precondition to obtain robust ultraviolet emission for optoelectronic applications.