Aromatic-imide-based thermally activated delayed fluorescence (TADF) materials with a twisted donor-acceptor-donor skeleton were efficiently synthesized and exhibited excellent thermal stability and high photoluminescence quantum yields. The small ΔE value (<0.1 eV) along with the clear temperature-dependent delayed component of their transient photoluminescence (PL) spectra demonstrated their excellent TADF properties. Moreover, the performance of organic light-emitting diodes in which TADF materials AI-Cz and AI-TBCz were used as dopants were outstanding, with external quantum efficiencies up to 23.2 and 21.1 %, respectively.

MTXSFCz with thermally activated delayed fluorescence is synthesized. Orange and red phosphorescent organic light-emitting diodes (PHOLEDs) with low efficiency roll-off exhibit external quantum efficiencies (EQE) up to 11.8% and 15.6%. The efficient upconversion from triplet to singlet of the host reduces the triplet density and thus affords a low efficiency roll-off of PHOLEDs.

Transformation of Na and K in a lignite was investigated during pyrolysis and gasification in a fixed-bed by using a serial dissolution method with H 2 O, CH 3 COONH 4 , and HCl solutions. The evolution of the fractions of four forms in solid and alkali volatilization during pyrolysis and gasification was determined. The results show that a different mode of occurrence between Na and of K in coal existed. Na in coal can be nearly completely dissolved by H 2 O, CH 3 COONH 4 , and HCl solution. However, K in coal exists almost in the stable forms. Both H 2 O soluble and CH 3 COONH 4 soluble Na and K fractions decline during pyrolysis and early gasification stage and increase a little with the process of char gasification. The stable form Na in the char produced during pyrolysis is transferred to other forms during char gasification via the pore opening and a series of chemical reactions. Na 2 SO 4 (K 2 SO 4 ) may play an important role in producing stable forms such as NaThe fraction of HCl soluble K increases during pyrolysis but decreases markedly during the early gasification stage.