Donor–Acceptor Star-Shaped Conjugated Macroelectrolytes: Synthesis, Light-Harvesting Properties, and Self-Assembly-Induced Förster Resonance Energy Transfer

Impact of π-Conjugation Length on the Excited-State Dynamics of Star-Shaped Carbazole-π-Triazine Organic Chromophores

Correlating star-shaped donor-bridge-acceptor (DBA) molecular structures with intramolecular charge transfer (ICT) and intersystem crossing (ISC) is essential to their application in photocatalysis, photovoltaics, and organic light-emitting diodes (OLEDs). In this work, we report a systematic photophysical study on a series of star-shaped triazine-phenylene-carbazole DBA molecules with 0, 1, and 2 bridging phenylene units (pTCT-0P, pTCT-1P, pTCT-2P). Using a combination of steady-state and time-resolved spectroscopy with time-dependent density functional theory (TDDFT), we find that the bridge length can strongly impact the structural conformation, ICT, and ISC. Global target analysis of the time-resolved spectroscopy reveals that pTCT-0P has the most favorable ISC rate of 1.96 × 10^-4 ps^-1, which is competitive with a singlet relaxation rate of 1.92 × 10^-4 ps^-1. TDDFT aligns with spectroscopic results within an order of magnitude, predicting an ISC rate of 2.1 × 10^-5 ps^-1 and revealing that the donor/acceptor orthogonalization concomitantly suppresses singlet exciton recombination and lowers the singlet-triplet energy gap. The new fundamental insights gained from this work will help design the next generation of star-shaped DBA-type molecules for photocatalytic and photoelectronic applications.

Fabrication of theranostic amphiphilic conjugated bottlebrush copolymers with alternating heterografts for cell imaging and anticancer drug delivery

We reported the first example of polyfluorene (PF)-backboned bottlebrush (bb) copolymers with alternating POEGMA/PCL hetero brushes for cancer theranostics.

Towards Monodisperse Star-Shaped Ladder-Type Conjugated Systems: Design, Synthesis, Stabilized Blue Electroluminescence, and Amplified Spontaneous Emission

A novel series of monodisperse star-shaped ladder-type oligo(p-phenylene)s, named as TrL-n (n=1-3), have been explored. Their thermal and electrochemical properties, fluorescence transients, photoluminescence quantum yields, density functional theory calculations, electroluminescence (EL) and amplified spontaneous emission (ASE) properties have been systematically investigated to unravel the molecular design on optoelectronic properties. The resulting materials showed excellent structural perfection, free of chemical defects, and exhibited great thermal stability (T_d : 404-418 °C and T_g : 147-184 °C) and amorphous glassy morphologies. Compared with their corresponding linear counterparts FL-m (m=1-3), TrL-n showed only little bathochromic shifts (5-12 nm) for the absorption maxima λ_max in both solution and films. The star-shaped ladder-type compounds exhibited enhanced optical stability and suppressed low-energy emission. Their EL spectra exhibited excellent stability with increasing the driving voltage from 6 to 12 V. Moreover, superior low ASE thresholds were recorded for TrL-n compared with FL-m. Rather low ASE threshold (29 nJ per pulse or 1.60 μJ cm^-2 ) was recorded for TrL-3, demonstrating their promising potential as excellent gain media. This study provides a novel design concept to develop monodisperse star-shaped ladder-type materials with excellent structural perfection, which are vital for shedding light on exploring robust organic emitters for optoelectronic applications.