New electroluminescent carbazole-containing conjugated polymer: Synthesis, photophysics, and electroluminescence

Donor-Acceptor Copolymers with 9-(2-Ethylhexyl)carbazole or Dibenzothiophene-5,5-dioxide Donor Units and 5,6-Difluorobenzo[c][1,2,5]thiadiazole Acceptor Units for Photonics

Semiconducting polymers, particularly of the third generation, including donor-acceptor (D-A) copolymers, are extensively studied due to their huge potential for photonic and electronic applications. Here, we report on two new D-A copolymers, CP1 and CP2, composed of different electron-donor (D) units: 9-(2-ethylhexyl)carbazole or dibenzothiophene-5,5-dioxide, respectively, and of 4,7-bis(4'-(2-octyldodecyl)thiophen-2'-yl)-5,6-difluorobenzo[c][1,2,5]thiadiazole building block with central 5,6-difluorobenzo[c][1,2,5]thiadiazole electron-acceptor (A) units, which were synthesized by Suzuki coupling in the high-boiling solvent xylene and characterized. The copolymers exhibited very good thermal and oxidation stability. A copolymer CP1 with different molecular weights was prepared in order to facilitate a comparison of CP1 with CP2 of comparable molecular weight and to reveal the relationship between molecular weight and properties. The photophysical, electrochemical, and electroluminescence properties were examined. Intense red photoluminescence (PL) with higher PL efficiencies for CP1 than for CP2 was observed in both solutions and films. Red shifts in the PL thin film spectra compared with the PL solution spectra indicated aggregate formation in the solid state. X-ray diffraction measurements revealed differences in the arrangement of molecules in thin films depending on the molecular weight of the copolymers. Light-emitting devices with efficient red emission and low onset voltages were prepared and characterized.

Carbazole-Fluorene Copolymers with Various Substituents at the Carbazole Nitrogen: Structure-Properties Relationship

Carbazole derivatives, carbazole-containing polymers and iridium complexes are of interest due to many possible applications in photonics, electronics and biology, particularly as active or hole-transporting layers in organic as well as perovskite devices due to their interesting properties. Here, a series of carbazole-fluorene conjugated copolymers with various substituents at the N-carbazole position (2-methoxycarbonylethyl, 2-carboxyethyl, 2-ethylhexyl, and nonan-2,4-dionatoiridium(III)bis(2-phenylpyridine-N,C^2')-9-yl) was prepared by Suzuki coupling. Their photophysical, electrochemical and electroluminescence (EL) properties were studied. Effects of molecular weight and substituents attached to carbazole unit on their properties are reported. The carbazole-fluorene copolymers in dilute solutions exhibited intense photoluminescence (PL) emission in the blue spectral region with high PL quantum yields (78-87%) except for the copolymer with the iridium complex (23%). Similar PL spectra were observed in dilute solutions. More pronounced differences were found in thin film PL and EL properties due to excimer/aggregate formation. Light-emitting devices (LEDs) made of copolymers with 2-ethylhexyl as N-carbazole substituent exhibited efficient EL emission with the best performance and the lowest EL onset voltages (3-4 V), while the LEDs made of copolymers with other substituents were not as efficient, but showed anomalous behavior and memory effects in current-voltage characteristics promising also for bio-inspired electronics.

Poly(carbazole-co-1,4-dimethoxybenzene): Synthesis, Electrochemiluminescence Performance, and Application in Detection of Fe3+

In this study, four polycarbazole derivatives (PCMB-Ds) with different alkyl side chains were designed and synthesized via Wittig–Horner reaction. A novel solid-phase electrochemiluminescence (ECL) system was prepared by immobilizing PCMB-D on an indium tin oxide (ITO) electrode with polyvinylidene fluoride (PVDF) in the presence of tripropylamine (TPrA). It could be found that the increase in alkyl side chain length had little effect on the ECL signal of PCMB-D, while the increase in the degree of polymerization (DP) greatly enhanced the ECL signal. Furthermore, the P-3/ITO ECL sensor based on the polyoctylcarbazole derivative (P-3) with the best ECL performance was successfully constructed and detected Fe³⁺ under the optimal experimental conditions. The ECL signal steadily diminished with the increased concentration of Fe³⁺ because of the competition and complexation between Fe³⁺ and P-3 under the condition of pH 7.4. This P-3/ITO platform could realize a highly sensitive and selective detection of Fe³⁺ with a wide detection range (from 6 × 10⁻⁸ mol/L to 1 × 10⁻⁵ mol/L) and low detection limit of 2 × 10⁻⁸ mol/L, which could allow the detection of Fe³⁺ in multiple scenarios, and would have a great application prospect.