Assessing the suitability of recovering shrub biowaste involved in wildland fires in the South of Europe through torrefaction mobile units.

Several types of shrubs and oak inducing high wildland fire risk in the South of Europe were evaluated for their potential valorization through torrefaction. Biomasses were firstly characterized in terms of macromolecular and elemental composition. Lab-scale TGA-GC/MS torrefaction experiments allowed the in-depth study of the solid mass transformation and the production profile of 23 volatile species (200 to 300 °C at 3 °C·min-1 and 300 °C for 30 min). The proportion of the torrefied products (solid, CO, CO2, water and volatile species) was evaluated through mass balance in a lab-scale furnace under typical torrefaction conditions (300 °C, 40 min). The results show a similar characterization and behavior in torrefaction for oak and shrublands, and slightly different characteristics for fern. However, fern may grow separately from shrublands and is considered to present a low fire risk. This suggests that the in-situ direct valorization of these biomasses through torrefaction mobile units seems promising. However, other properties, such as density, flowability and grindability need to be studied to confirm the feasibility of the process. Regarding torrefaction products, a higher carbon content and an interesting increase in heating value were measured for the torrefied solid, which makes it suitable for energetic valorization, among other uses. The composition of permanent gases was evaluated and found in agreement with previous studies. Finally, the volatile species released were studied in function of the torrefaction temperature, in view of their possible valorization as green chemicals.

Electron-Rich 4-Substituted Spirobifluorenes: Toward a New Family of High Triplet Energy Host Materials for High-Efficiency Green and Sky Blue Phosphorescent OLEDs.

We report herein a detailed structure-properties relationship study of the first examples of electron-rich 4-substituted spirobifluorenes for organic electronic applications, namely, 4-phenyl-N-carbazole-spirobifluorene (4-PhCz-SBF) and 4-(3,4,5-trimethoxyphenyl)-spirobifluorene (4-Ph(OMe)3-SBF). The incorporation of the electron-rich moieties in the ortho position of the biphenyl linkage (position C4) induces unique properties, very different from those previously described in the literature for this family of semiconductors. Both dyes can be readily synthesized, possess high triplet energies and excellent thermal stability, and their HOMO energy levels are highly increased compared to those of other 4-substituted SBFs. We also provide in this work the first rationalization of the peculiar fluorescence of 4-substituted SBFs. Finally, the present dyes have been successfully incorporated as host in green and blue phosphorescent organic light-emitting diodes with high performance either for the green (EQE of 20.2%) or the blue color (EQE of 9.6%). These performances are, to the best of our knowledge, among the highest reported to date for 4-substituted SBF derivatives.

9H-Quinolino[3,2,1-k]phenothiazine: A New Electron-Rich Fragment for Organic Electronics.

A new electron-rich fragment, namely the quinolinophenothiazine (QPTZ) is reported. The QPTZ fragment incorporated in spiroconfigured materials leads to higher performance in blue Phosphorescent OLEDs than structurally related phenylacridine and indoloacridine based materials (increasing the HOMO energy level, modulating the spin-orbit coupling, etc.) and leads to highly efficient blue phosphorescent organic light emitting diodes, indicating the strong potential of this new molecular fragment in organic electronics.

Modulation of the Physicochemical Properties of Donor-Spiro-Acceptor Derivatives through Donor Unit Planarisation: Phenylacridine versus Indoloacridine-New Hosts for Green and Blue Phosphorescent Organic Light-Emitting Diodes (PhOLEDs).

This work reports a detailed structure-property relationship study of a series of efficient host materials based on the donor-spiro-acceptor (D-spiro-A) design for green and sky-blue phosphorescent organic light-emitting diodes (PhOLEDs). The electronic and physical effects of the indoloacridine (IA) fragment connected through a spiro bridge to different acceptor units, namely, fluorene, dioxothioxanthene or diazafluorene moiety, have been investigated in depth. The resulting host materials have been easily synthesised through short, efficient, low-cost, and highly adaptable synthetic routes by using common intermediates. The dyes possess a very high triplet energy (ET ) and tuneable HOMO/LUMO levels, depending on the strength of the donor/acceptor combination. The peculiar electrochemical and optical properties of the IA moiety have been investigated though a fine comparison with their phenylacridine counterparts to study the influence of planarisation. Finally, these molecules have been incorporated as hosts in green and sky-blue PhOLEDs. For the derivative SIA-TXO2 as a host, external quantum efficiencies as high as 23 and 14 % have been obtained for green and sky-blue PhOLEDs, respectively.

Spirobifluorene-2,7-dicarbazole-4'-phosphine Oxide as Host for High-Performance Single-Layer Green Phosphorescent OLED Devices.

A new host material based on the 2,7,4'-substituted spirobifluorene platform has been designed and used in single-layer phosphorescent OLED with very high efficiency (EQE = 13.2%) and low turn-on voltage (2.4 V). This performance is among the best reported for green single-layer PhOLEDs and may open new avenues in the design of host materials for single-layer devices.

ortho-, meta-, and para-dihydroindenofluorene derivatives as host materials for phosphorescent OLEDs.

This work reports the first structure-properties relationship study of ortho [2,1-c]-, meta [1,2-a]-, and para [1,2-b]dihydroindenofluorenes, highlighting the influence of bridge rigidification on the electronic properties. This study has made it possible to devise an extended π-conjugated molecule with both a high triplet state energy level and excellent thermal and morphological stability. As a proof of concept, dihydroindenofluorenes were used as the host in sky-blue phosphorescent organic light-emitting diodes (PhOLEDs) with high performance.