New molecular dyads containing perylenediimide (PTCDI) as an electron acceptor and carbazolyl derivative as an electron donor have been successfully synthesized. Cyclic voltammetry and absorption spectroscopy show that both electroactive units preserve their intrinsic nature, whereas photophysical investigations display a efficient fluorescence quenching. The molecular dyads such as 4 and 5 exhibited unique electronic energy levels to facilitate the photoinduced electron transfer process.
Diketopyrrolopyrrole (DPP)-based conjugated polymer (P(DPP-BDT)) containing benzodithiophene (BDT) was successfully synthesized via Stille coupling reaction. The synthesized polymer shows good solubility in common organic solvents and good self-film-forming properties. The electrical properties of the polymer were evaluated in organic thin film transistors (OTFTs). The TFT made of pristine P(DPP-BDT) film exhibits good carrier mobility of 0.38∼0.40 cm2 V−1 s−1 (Ion/off = 106, Vth = −9 V), which is close to the mobility of TFT made of the thermally annealed film.
A light-emitting molecular triad (BPCP-2CPC) with dual functionality was successfully synthesized and applied to solution-processed non-doped organic light-emitting diodes. The BPCP-2CPC triad contains 9-phenyl-9H-carbazole units as a host moiety tethered to a green-emitting core (BPCP) through a cyclohexane unit and exhibits thermally activated delayed fluorescence (TADF) and aggregation-induced emission (AIE) characteristics simultaneously. The BPCP-2CPC-based non-doped TADF-OLED devices showed a high external quantum efficiency (EQE) of 13.4%.
All‐polymer photovoltaics (all‐PPVs) that operate under both indoor and outdoor lighting conditions require active layers with appropriately adjusted optical‐absorption ranges. However, the optical absorption of a conventional donor–acceptor binary blend is restricted to the combined absorption bands of its components. Herein, a new conjugated block copolymer (CBC) acceptor, b ‐PYT, is designed by integrating polymer acceptor blocks of wide and narrow bandgaps in a single structure. Such combination results in the wide absorption range (550–850 nm) of b ‐PYT that matches the emission of both artificial and solar light. The b ‐PYT CBC acceptor is more crystalline than the corresponding random terpolymer, r ‐PYT, owing to improved interactions between its macromolecular acceptor units. Despite exhibiting slightly inferior outdoor performance compared to that of devices using the homopolymer BTTP‐T, the PM6: b ‐PYT‐based devices deliver superior power conversion efficiency (PCE) under indoor light‐emitting diode (LED) light owing to better matched absorption and emission spectra of b ‐PYT and a cold white LED, respectively. Additionally, it is worth highlighting that PM6: b ‐PYT‐based all‐PPVs can maintain approximately 87% of the initial PCE even after 600 min of thermal aging at 150 °C, which demonstrates the superior thermal stability compared with those of all‐PPVs that use traditional binary active layers.
Two novel polymeric host materials, P(NmCP) and P(mCP), were synthesized, and high-performing sky-blue and green thermally activated delayed fluorescence organic light-emitting diodes were achieved.
Coherent phonon oscillations in the UV-Vis transient absorption and circular dichroism response of two chiral polyfluorene-based copolymer thin films are investigated. A slow oscillation in the hundred picosecond regime indicates the propagation of a longitudinal acoustic phonon with a frequency in the gigahertz range through cholesteric films of PFPh and PFBT, which allow for the optical determination of the longitudinal sound velocity in these polymers, with values of (2550 ± 140) and (2490 ± 150) m s−1, respectively. The oscillation is induced by a strain wave, resulting in a pressure-induced periodic shift of the electronic absorption bands, as extracted from a Fourier analysis of the transient spectra. The acoustic phonon oscillation is also clearly detected in the transient circular dichroism (TrCD) response of PFPh, indicating a transient pressure-induced shift of the CD spectrum and possibly also phonon-induced chirality changes via pitch length modulation of the cholesteric helical polymer stack.
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