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[Display omitted] • "Asymmetric D-A-wA" strategy is demonstrated for high-efficiency red TADF emitters. • Diphenylphosphine oxide as the second acceptor markedly improves TADF properties. • Strong red emission peaked at 645 nm with a high PLQY of 94.7 % is realized. • The maxima of 19360 cd m−2 for luminance and 11.4 % for EQE at 632 nm are achieved. A feasible strategy of asymmetric donor–acceptor-second acceptor (D-A-A) structure is proposed for improving the photoluminecense (PL) and electroluminescence (EL) performance of red thermally activated delayed fluorescence (TADF) emitters. As a concept, four newly TADF emitters are designed and synthesized, D-A-A structure o TPAPO-DTPZ and p TPAPO-DTPZ and D-A-D type o DTPA-DTPZ and p DTPA-DTPZ, by using triphenylamine (TPA), dithieno[2,3- a :3′,2′- c ]phenazine (DTPZ) and diphenylphosphine oxide (DPPO) groups as the donor, acceptor and second acceptor, respectively. It is demonstrated that abound intra- and inter-molecular C H···O hydrogen bonds are forming between TPA donor and DPPO acceptor for the asymmetric compounds, which effectively promote the intra- and inter-molecular charge transfer. Moreover, the steric hindrance of DPPO group availably suppresses the concentration quenching. As a consequence, the asymmetric D-A-A structured o TPAPO-DTPZ and p TPAPO-DTPZ exhibit relatively higher PL quantum yields and lower nonradiation rates, and thus better EL performance. In particular, device based on p TPAPO-DTPZ achieves the maximum luminance of 19360 cd m−2 and external quantum efficiency of 11.4 % at 632 nm, which are 2.3 and 1.5 times the values of p DTPA-DTPZ based device. [ABSTRACT FROM AUTHOR]

[Display omitted] • Near-infrared TADF emission from phenanthroline based molecule is demonstrated. • NIR emission and radiation efficiency are balanced in CNPP-TPA. • Strong NIR emission peaked at 701 nm with PLQY of 96.5% is realized. • A maximum EQE (8.69%) of vacuum-evaporated device peaked at 684 nm is achieved. • A maximum EQE (2.02%) of spin-coated device peaked at 700 nm is achieved. Efficient thermally activated delayed fluorescence (TADF) emitters are of practical significance for realizing high-performance organic light emitting diodes (OLEDs), which remains the great challenge for near-infrared (NIR) emitters because of their narrow bandgap worsened non-radiative transition. Herein, a NIR TADF molecule (CNPP-TPA) is reported, composed of 2,3-dicyanopyrazino phenanthroline (CNPP) as acceptor and triphenylamine as donor. The strong electron-withdrawing effect of CNPP and intramolecular hydrogen bond endow CNPP-TPA with efficient NIR photoluminescence emission peaked at 701 nm with a high photoluminescence quantum yield of 96.5%, owing to rapid singlet radiation and effective reverse intersystem crossing. Vacuum -evaporated and spin-coated organic light-emitting diodes exhibit the NIR emissions respectively peaked at 684 nm and 700 nm, corresponding to Commission International de L'Eclairage (CIE) coordinates of (0.68, 0.31) and (0.69, 0.30), respectively. Significantly, these two devices achieved the state-of-the-art external quantum efficiencies of 8.69% and 2.02%. [ABSTRACT FROM AUTHOR]

Construction of Schottky junctions based DUT-67 and Pd nanosheet with enhanced charge carrier separation efficiency for efficient photoreduction of CO 2. [Display omitted] • DUT-67 decorated with Pd nanosheet was prepared. • 0.3-Pd/DUT-67 had considerable photocatalytic CO 2 reduction to CO efficiency of 48.6 μmol g−1. • Schottky barrier at Pd/DUT-67 interface boosts separation of electron-hole pairs. The separation, transfer and recombination of charge often affect the rate of photocatalytic reduction of CO 2. Schottky junctions can promote the rapid separation of space charge. Therefore, in this paper, Pd nanosheets were grown on the surface of DUT-67 by a hydrothermal method, and a Schottky junction was constructed between DUT-67 and Pd. Under the action of the Schottky junction, the CO yield of 0.3-Pd/DUT-67 reached 12.15 μmol/g/h, which was 17 times higher than that of DUT-67. Efficient charge transfer was demonstrated in photochemical experiments. The large specific surface area and the increased light utilization rate also contributed to the increase in the CO 2 reduction efficiency. In addition, the mechanism of Pd/DUT-67 photocatalytic reduction of CO 2 was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • The UCN@ZIS/SWNTs composite with different V Zn concentrations was constructed for photocatalytic CO 2 reduction. • The UCN was acidified to regulate the surface-active site for CO 2 activation and H 2 O dissociation. • The SWNTs further improves the separation efficiency of photogenerated electron-hole pairs by providing charge transfer channels. • The UCN@rZIS/SWNTs composite displays excellent photocatalytic performance and CH 4 selectivity. Zinc vacancy (V Zn) concentrations were successfully regulated on the hierarchical flower spherical ZnIn 2 S 4 (ZIS) by controlling the hydrothermal temperature. The photo-electrochemical experiments indicated that the carrier separation efficiency of ultrathin-g-C 3 N 4 @ZIS/SWNTs (UCN@ZIS/SWNTs) composite with different V Zn concentrations (poor-V Zn ZIS (pZIS) and rich-V Zn ZIS (rZIS)) had an efficient improvement because of the construction of UCN@ZIS heterojunction and the multiple channels for charge transfer provided by SWNTs. In-situ FTIR results indicate that the presence of V Zn and the enriched surface-active site on UCN contributes to CO 2 activation and H 2 O dissociation. Additionally, the yield of CO and CH 4 over UCN@rZIS/SWNTs composite reached 33.7 µmol g−1 and 39.8 µmol g−1, respectively, and the selectivity of CH 4 reached 54.1 % under the synergistic effect of V Zn , the surface-active site of UCN and charge-transfer channels. This work established an ideal defect model for enhancing CO 2 photocatalytic reduction performance and product selectivity, which may provide a new way to improve photocatalytic efficiency and a better understanding of the photocatalytic reaction mechanisms. [ABSTRACT FROM AUTHOR]

The 3D hierarchical structure of CdS/Ni-MOF inhibits the agglomeration of CdS, improve light harvesting, increase active surface area, reaction sites, promote charge transfer and separation, which greatly improves the efficiency of CO 2 conversion. However, when the CdS is overloaded and its hierarchical structure is destroyed, the heterostructure plays a major role in improving the performance. Based on the above results, we propose the preliminary mechanism of 20%-CdS/Ni-MOF photocatalytic reduction of CO 2. Firstly, under UV–Vis illumination, Ni-MOF and CdS are excited to produce electrons (e−) and holes (h+). Then, because of the tight interface contact, the e- excited by Ni-MOF could be transferred to CdS with more positive CB, and CdS as the active site could reduce CO 2 to CO more effectively. At the same time, the h+ in the VB of Ni-MOF and CdS participate in the oxidation reaction to produce O 2 and H 2 O 2 , which achieving the elimination of holes. Such charge separation and transfer of the electron-hole pairs facilitate enhanced photocatalytic activity. [Display omitted] • The 3D hierarchical heterostructure was synthesized by a simple strategy. • 20%-CdS/Ni-MOF showed excellent performance in the vapor–solid reaction system. • The hierarchical structure and heterostructure of CdS/Ni-MOF play a synergistic role. Fabricating the hierarchical heterostructure is efficient way for enhancing CO 2 conversion of semiconductor photocatalysts. Herein, a simple strategy has been employed to prepare several 3D hierarchical CdS/Ni-MOF heterostructure photocatalysts, and the selective photoreduction of CO 2 to CO under simulated sunlight in the gas–solid phase reactor. Among the prepared photocatalysts, 20%-CdS/Ni-MOF shows the best CO yield, which was 16 times and 7 times that of Ni-MOF and CdS, respectively. By controlling the morphology of the catalyst, we found that the significant improvement in photocatalytic activity can be ascribed to the synergistic effect of heterostructure in CdS/Ni-MOF and its unique hierarchical structure, which can improve the efficiency of charge transmission and provides abundant active sites, etc. Finally, the preliminary photocatalytic mechanism was discussed by in situ FTIR and liquid ultraviolet spectrophotometer. [ABSTRACT FROM AUTHOR]