A porphyrin pentamer as a bright emitter for NIR OLEDs

The luminescence and electroluminescence of an ethyne-linked zinc(ii) porphyrin pentamer have been investigated, by testing blends in two different conjugated polymer matrices, at a range of concentrations. The best results were obtained for blends with the conjugated polymer PIDT-2TPD, at a porphyrin loading of 1 wt%. This host matrix was selected because the excellent overlap between its emission spectrum and the low-energy region of the absorption spectrum of the porphyrin oligomer leads to efficient energy transfer. Thin films of this blend exhibit intense fluorescence in the near-infrared (NIR), with a peak emission wavelength of 886 nm and a photoluminescent quantum yield (PLQY) of 27% in the solid state. Light-emitting diodes (LEDs) fabricated with this blend as the emissive layer achieve average external quantum efficiencies (EQE) of 2.0% with peak emission at 830 nm and a turn-on voltage of 1.6 V. This performance is remarkable for a singlet NIR-emitter; 93% of the photons are emitted in the NIR (λ > 700 nm), indicating that conjugated porphyrin oligomers are promising emitters for non-toxic NIR OLEDs

A porphyrin pentamer as a bright emitter for NIR OLEDs

The Luminescence and electroluminescence of an ethyne-Linked zinc(II) porphyrin pentamer have been investigated, by testing blends in two different conjugated polymer matrices, at a range of concentrations. The best results were obtained for blends with the conjugated polymer PIDT-2TPD, at a porphyrin loading of 1 wt%. This host matrix was selected because the excellent overlap between its emission spectrum and the low-energy region of the absorption spectrum of the porphyrin oligomer leads to efficient energy transfer. Thin films of this blend exhibit intense fluorescence in the near-infrared (NIR), with a peak emission wavelength of 886 nm and a photoluminescent quantum yield (PLQY) of 27% in the solid state. Light-emitting diodes (LEDs) fabricated with this blend as the emissive layer achieve average external quantum efficiencies (EQE) of 2.0% with peak emission at 830 nm and a turn-on voltage of 1.6 V. This performance is remarkable for a singlet NIR-emitter; 93% of the photons are emitted in the NIR (lambda > 700 nm), indicating that conjugated porphyrin oligomers are promising emitters for non-toxic NIR OLEDs

Towards efficient near-infrared fluorescent organic light-emitting diodes

The energy gap law (EG-law) and aggregation quenching are the main limitations to overcome in the design of nearinfrared (NIR) organic emitters. Here, we achieve unprecedented results by synergistically addressing both of these limitations. First, we propose porphyrin oligomers with increasing length to attenuate the effects of the EG -law by suppressing the non-radiative rate growth, and to increase the radiative rate via enhancement of the oscillator strength. Second, we design side chains to suppress aggregation quenching. We find that the logarithmic rate of variation in the non-radiative rate vs. EG is suppressed by an order of magnitude with respect to previous studies, and we complement this breakthrough by demonstrating organic light-emitting diodes with an average external quantum efficiency of ~1.1%, which is very promising for a heavy-metal-free 850 nm emitter. We also present a novel quantitative model of the internal quantum efficiency for active layers supporting triplet-to-singlet conversion. These results provide a general strategy for designing high-luminance NIR emitters

Highly Luminescent Encapsulated Narrow Bandgap Polymers Based on Diketopyrrolopyrrole.

We present the synthesis and characterization of a series of encapsulated diketopyrrolopyrrole red-emitting conjugated polymers. The novel materials display extremely high fluorescence quantum yields in both solution (>70%) and thin film (>20%). Both the absorption and emission spectra show clearer, more defined features compared to their naked counterparts demonstrating the suppression of inter and intramolecular aggregation. We find that the encapsulation results in decreased energetic disorder and a dramatic increase in backbone colinearity as evidenced by scanning tunnelling microscopy. This study paves the way for diketopyrrolopyrrole to be used in emissive solid state applications and demonstrates a novel method to reduce structural disorder in conjugated polymers

The effect of hypoxemic resuscitation of hemorrhagic shock on hemodynamic stabilization and inflammatory response: A pilot study in a rat experimental model

Background: Resuscitation of hemorrhagic shock is associated with tissue injury. The effect of hypoxemia during resuscitation was investigated. Methods: Shock was induced by withdrawing blood to mean arterial pressure (MAP) 40 mm Hg and maintained for 60 minutes in 25 Wistar rats. Animals were randomly divided to receive either normoxemic (controls, FiO(2) = 21%, n = 14) or hypoxemic (HypRes, FiO(2) = 12%, n = 11) resuscitation by re-infusing their shed blood. Outcome was assessed through hemodynamic and inflammatory parameters. Another nine rats served to correlate different FiO(2) to the corresponding PaO2. Results: At 60 minutes of resuscitation HypRes had higher MAP than control animals (p = 0.008). The respective median (range) malondialdehyde and TNF-alpha levels was 1.7 (1-2.1) versus 3.1 (2.4-4.3) fimol/L, (p = 0.02) and 0 versus 5.8 (0-5.8) pg/mL, (p = 0.025). Glutathione, endotoxin, interferon-gamma, and nitric oxide values were similar between groups. FiO(2) of 12% induced only a mild hypoxemia (PaO2 similar to 80 mm Hg). Conclusions: Even mild hypoxemia during resuscitation of shock leads to effective hemodynamic stabilization. Key Words: Hemorrhagic shock, Glutathione, Endotoxin, Tumor necrosis factor-alpha, Interferon-gamma, Nitric oxide, Malondialdehyde, Hypoxemic resuscitation

Highly Luminescent Encapsulated Narrow Bandgap Polymers Based on Diketopyrrolopyrrole

We present the synthesis and characterization of a series of encapsulated diketopyrrolopyrrole red-emitting conjugated polymers. The novel materials display extremely high fluorescence quantum yields in both solution (>70%) and thin film (>20%). Both the absorption and emission spectra show clearer, more defined features compared to their naked counterparts demonstrating the suppression of inter and intramolecular aggregation. We find that the encapsulation results in decreased energetic disorder and a dramatic increase in backbone colinearity as evidenced by scanning tunnelling microscopy. This study paves the way for diketopyrrolopyrrole to be used in emissive solid state applications and demonstrates a novel method to reduce structural disorder in conjugated polymers

Highly Luminescent Encapsulated Narrow Bandgap Polymers Based on Diketopyrrolopyrrole

We present the synthesis and characterization of a series of encapsulated diketopyrrolopyrrole red-emitting conjugated polymers. The novel materials display extremely high fluorescence quantum yields in both solution (>70%) and thin film (>20%). Both the absorption and emission spectra show clearer, more defined features compared to their naked counterparts demonstrating the suppression of inter and intramolecular aggregation. We find that the encapsulation results in decreased energetic disorder and a dramatic increase in backbone colinearity as evidenced by scanning tunnelling microscopy. This study paves the way for diketopyrrolopyrrole to be used in emissive solid state applications and demonstrates a novel method to reduce structural disorder in conjugated polymers