Search

π-Stacked dendrimers consisting of cofacially aligned donors and acceptors are developed by introducing three dendritic teracridan donors with orthogonal configuration and three triazine acceptors in periphery of hexaphenylbenzene skeleton. The dendritic structure and orthogonal configuration of teracridan not only make their outer acridan segments approaching to acceptor in close distance, but also fix donor and acceptor in face-to-face alignment, leading to through-space charge transfer emission with thermally activated delayed fluorescence (TADF) effect. By regulating charge transfer strength via substituent effect of acceptor, emission color of the dendrimers can be tuned from blue to yellow/red region. Solution-processed two-color white organic light-emitting diodes (OLEDs) based on blue and yellow π-stacked donor-acceptor dendrimers exhibit the maximum external quantum efficiency of 20.6 % and maximum power efficiency of 58.9 lm W-1 , representing the state-of-the-art efficiency for all-TADF white OLEDs by solution process.

Polymer light-emitting diodes (PLEDs) based on thermally activated delayed fluorescence (TADF) emitters show great potential in developing high-efficiency solution-processed light-emitting devices ...

Through-space charge transfer polynorbornenes with fixed and controllable spatial alignment of donor and acceptor in edge-to-face/face-to-face stacking patterns are developed for achieving high-efficiency blue thermally activated delayed fluorescence (TADF). The alignment is realized by using the cis, exo-configuration of norbornene to confine donor and acceptor in close proximity, and utilizing orthogonal and dendritic structures of donors to provide either perpendicular or parallel stacking motif relative to acceptors. Compared to edge-to-face counterparts, polynorbornenes with face-to-face aligned donor and acceptor exhibit much larger oscillator strength and higher photoluminescence quantum yield. The resulting polymers exhibit deep blue (422 nm) to sky blue (482 nm) emission and TADF effect with reverse intersystem crossing rates of 0.4-5.9×106 s-1 , giving the maximum external quantum efficiency of 18.8 % for non-doped blue organic light-emitting diodes by solution process.

Single white light-emitting polymers (SWPs) represent a high-fidelity system for generating white light emission from polymers without phase separation compared to polymer blend systems. However, their device performance so far has been limited because of the unwanted hole scattering caused by an energy-level mismatch between emitters and hosts, and the large injection barrier at the polymer/anode interface. Here, we report novel poly(arylene phosphine oxide)-based all-phosphorescent SWPs by using the combination of a high-HOMO-level blue phosphor and high-HOMO-level poly(arylene phosphine oxide) host to achieve a low turn-on voltage of 2.8 V, high external quantum efficiency of 18.0% and remarkable power efficiency of 52.1 lm W−1, which makes them the most efficient SWPs so far. This record power efficiency is realized by using the high-HOMO-level blue phosphor to eliminate the hole scattering effect and by using the high-HOMO-level polymer host to reduce the hole injection barrier. This result represents an important progress in SWPs to achieve efficiency surpassing that of the polymer blends currently used for solution-processed white organic light-emitting diodes (WOLEDs) and even comparable with that of the small molecules used for vacuum-deposited WOLEDs.

The buildup of uncaptured fly ash particles from wet flue gas desulfurization (WFGD) system in post-combustion CO 2 capture processes is an important issue in existing coal-fired power plants. A self-designed lab-scale packed column filled with θ-ring packing was used to investigate the influence of fly ash particles on the volumetric overall mass-transfer coefficient K G a v using K 2 CO 3 absorbent. The affecting laws of fly ash particles on the K G a v were discussed under different operating conditions such as the solution temperature, the liquid-gas ratio L/G and the concentration of fly ash particles. The results showed that the effect of two types of fly ash particles on the outlet CO 2 concentration mainly occurred at the early period of the experimental process, while the effect extent of the Inner Mongolia ash was larger than Nanjing ash. The solution temperature and the liquid-gas ratio had a significant role in promoting the K G a v , but the presence of fly ash particles in K 2 CO 3 solution markedly reduced the K G a v . The influence of fly ash particles on the K G a v was independent of its chemical compositions, but was related to the operating parameters. With the solution temperature increasing, the influence of fly ash particles on the K G a v was weakened but, conversely, was increased with the liquid-gas ratio increasing. Change range of the K G a v was smaller and finally reached a stable state as the fly ash particles concentration increases. The analysis results indicated that the influence of the ash particles was realized via changing the initial distribution of the absorption solution.

The molecular composition, stable carbon and hydrogen isotopes, and light hydrocarbons of the Lower Paleozoic natural gas in the Daniudi gas field in the Ordos Basin were investigated to study the geochemical characteristics. The Lower Paleozoic gas in the Daniudi gas field displays methane contents of 87.41–93.34%, dryness coefficients (C1/C1–5) ranging from 0.886 to 0.978, δ13C1 and δ13C2 values ranging from −40.3 to −36.4‰, with an average of −38.3‰, and from −33.6 to −24.2‰, with an average of −28.4‰, respectively, and δD1 values ranging from −197 to −160‰. The alkane gas generally displays positive carbon and hydrogen isotopic series, and the C7 and C5–7 light hydrocarbons of the Lower Paleozoic gas are dominated by methylcyclohexane and iso-alkanes, respectively. The Lower Paleozoic gas in the Daniudi gas field is mixed from coal-derived and oil-associated gases, similar to that observed in the Jingbian gas field. The oil-associated gas in the Lower Paleozoic gas is secondary oil cracking gas and displays a lower cracking extent than that in the Jingbian gas field. The coal-derived gas in the Lower Paleozoic gas in the Daniudi gas field migrated from the Upper Paleozoic gas through the window area where the iron–aluminum mudstone caprocks in the Upper Carboniferous Benxi Formation were missing. The oil-associated gas in the Lower Paleozoic gas in the Daniudi gas field was probably derived from presalt source rocks in the Lower Ordovician Majiagou Formation rather than the limestone in the Upper Carboniferous Taiyuan Formation. It seems unlikely that the marlstone in the Upper Ordovician Beiguoshan Formation and shale in the Middle Ordovician Pingliang Formation on the western and southwestern margins of the Ordos Basin contributed to the oil-associated gas in the Lower Paleozoic gas in the Daniudi gas field.

Trace elements (TEs) emitted from coal-fired power plants have caused widespread concern. The onsite investigation of TEs emission from a Chinese 660 MW pulverized coal (PC) boiler equipped with selective catalytic reduction (SCR), electric submersible pump (ESP), wet flue gas desulfurization (WFGD), and wet electrostatic precipitator (WESP) was conducted by using U.S. Environmental Protection Agency Method 29. Simultaneous sampling of the coal, bottom ash, ESP ash, flue gas, and by-products from WFGD and WESP processes was performed. Results show that TEs mass balance rates for the entire system, furnace and each air pollution control device (APCD), are in the acceptable range of 70–130%, which confirms the validity and reliability of the field test data. The studied TEs are mainly distributed in bottom and ESP ash with the ratios of 2.11–12.15% and 87.83–97.83%, respectively, while little amounts of them exist in WFGD, WESP, and the stack. Coal combustion by-products such as bottom ash and gypsum have l...

Through-space charge transfer hexaarylbenzene dendrimers containing circularly-arrayed electron donors and acceptors exhibit thermally activated delayed fluorescence and aggregation-induced emission effects, giving EQE of 14.2% for solution-processed OLEDs., Through-space electron interaction plays a critical role in determining the optical and charge transport properties of functional materials featuring π-stacked architectures. However, developing efficient organic luminescent materials with such interactions has been a challenge because of the lack of well-established prototypical molecules. Here we report the design of through-space charge transfer hexaarylbenzenes (TSCT-HABs) containing circularly-arrayed electron donors (acridan/dendritic triacridan) and acceptors (triazine), which exhibit both thermally activated delayed fluorescence (TADF) and aggregation-induced emission (AIE) effects for high-efficiency solution-processed organic light-emitting diodes (OLEDs). Spatial separation of donors and acceptors in the TSCT-HABs induces a small singlet–triplet energy splitting of 0.04–0.08 eV, leading to delayed fluorescence with microsecond-scale lifetimes. Meanwhile, the TSCT-HABs display the AIE effect with emission intensity enhanced by 6–17 fold from solution to the aggregation state owing to their propeller-shaped configuration. Solution-processed OLEDs based on the TSCT-HABs show maximum external quantum efficiency up to 14.2%, making them among the most efficient emitters for solution-processed TADF OLEDs.