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Abstract Fast spin-flipping is the key to exploit the triplet excitons in thermally activated delayed fluorescence based organic light-emitting diodes toward high efficiency, low efficiency roll-off and long operating lifetime. In common donor-acceptor type thermally activated delayed fluorescence molecules, the distribution of dihedral angles in the film state would have significant influence on the photo-physical properties, which are usually neglected by researches. Herein, we find that the excited state lifetimes of thermally activated delayed fluorescence emitters are subjected to conformation distributions in the host-guest system. Acridine-type flexible donors have a broad conformation distribution or bimodal distribution, in which some conformers feature large singlet-triplet energy gap, leading to long excited state lifetime. Utilization of rigid donors with steric hindrance can restrict the conformation distributions in the film to achieve degenerate singlet and triplet states, which is beneficial to efficient reverse intersystem crossing. Based on this principle, three prototype thermally activated delayed fluorescence emitters with confined conformation distributions are developed, achieving high reverse intersystem crossing rate constants greater than 106 s−1, which enable highly efficient solution-processed organic light-emitting diodes with suppressed efficiency roll-off.

Abstract To achieve highly‐efficient organic light‐emitting diodes (OLEDs), great efforts have been devoted into constructing thermally activated delayed fluorescence (TADF) with high horizontal dipole ratios (Θ//). Here, we proposed a design strategy by integrating a rigid electron‐accepting oxygen‐bridged boron core with triple electron‐donating groups, which exhibited a “shamrock‐shape”, namely BO‐3DMAC and BO‐3DPAC. Benefiting from the rigid and large‐planar skeletons brought by shamrock‐shaped design, BO‐3DMAC and BO‐3DPAC exhibit high Θ// of 84%/70% and 93%/94% in neat/doped films, respectively, and finally furnish excellent external quantum efficiencies (EQEs) of up to 28.3% and 38.7% in 20 wt% doped OLEDs with sky‐blue emission, as well as adequate EQEs of up to 21.0% and 16.7% in nondoped OLEDs. This work unveils a promising strategy to establish high‐Θ// TADF emitters by constructing large‐planar molecular structures using shamrock‐shaped design.

In this study, gluten, glutenin and gliadin were mixed with starch at mass ratio of 14:86. To clarify their effects and mechanism on starch digestibility, the interactions between gluten and its components and starch/α-amylase were investigated by a rheometer, a thermogravimetric analyzer and a confocal laser scanning microscope (CLSM). The results showed that compared with pure wheat starch, the digestibility of starch reduced by 39.93%, 49.48% and 26.61% after 120 min of enzymatic hydrolysis in the presence of gluten, glutenin and gliadin, respectively. Starch could interact with gluten through hydrogen bonds to form a stable complex. Compared with gluten and gliadin, the addition of glutenin formed a denser physical barrier around the starch matrix, which inhibited the enzymatic hydrolysis of starch to a greater extent. In addition, the percentage inhibition of glutenin on α-amylase was the highest (approximately 79%). CLSM observation proved stronger binding between α-amylase and glutenin. The results of this study will help to enrich our understanding of the mechanism of the regulatory effect of typical protein components on starch digestibility in food systems, and provide a theoretical guideline for the development of low-glycemic-index foods.