中国EFL学习者冠词产出的主(客)观实指性效应研究

与名词性成分相关的实指性由辖域关系和主观世界的认知两个维度界定,本文分别称为客观实指性和主观实指性,而对于这两类实指性在中国EFL学习者英语冠词习得的效应研究仍有分歧。本文采用诱导产出法考察120名中国英语学习者在五种指称类型的名词性成分中的冠词产出状况。实验数据表明,客观实指性和主观实指性对各组受试在定指的两个指称类型冠词产出的效应差异不显著;不定指类型中,受试在主观实指与客观实指的冠词产出效应差异不显著,而在不定非实指与不定主观实指以及不定客观实指名词成分类型的冠词使用准确率差异显著。结果证实中国EFL学习者英语冠词产出时客观实指性效应显著,而主观实指性在中国学习者英语冠词的产出效应不显著。

Through-space charge transfer blue polymers containing acridan donor and oxygen-bridged triphenylboron acceptor for highly efficient solution-processed organic light-emitting diodes

Three kinds of through-space charge transfer(TSCT)blue polymers containing non-conjugated polystyrene backbone together with spatially-separated acridan donor and oxygen-bridged triphenylboron acceptors having different substituents of tert-butyl,hydrogen and fluorine are designed and synthesized.The designed TSCT blue polymers possess photoluminescence quantum yields up to 70%in solid-state film,single-triplet energy splitting below 0.1 eV,and typical thermally activated delayed fluorescence(TADF)effect.Meanwhile,the resulting polymers exhibit aggregation-induced emission(AIE)effect with emission intensity increased by up to^27 folds from solution to aggregation state.By changing the substituent of acceptors to tune the charge transfer strength,blue emission with peaks from 444 to 480 nm can be realized for the resulting polymers.Solution-processed organic light-emitting diodes based on the polymers exhibit excellent device performance with Commission Internationale de L’Eclairage(CIE)coordinates of(0.16,0.27),together with the maximum luminous efficiency of 30.7 cd A-1 and maximum external quantum efficiency of 15.0%,which is the best device efficiency for blue TADF polymers.

Alkoxy encapsulation of carbazole-based thermally activated delayed fluorescent dendrimers for highly efficient solution-processed organic light-emitting diodes

Two n-butoxy-encapsulated dendritic thermally activated delayed fluorescent(TADF) emitters(namely O-D1 and O-D2) with the first-/second-generation carbazoledendrons are designed and synthesized via C—N coupling between carbazoledendrons and 2,4,6-tris(4-bromophenyl)-1,3,5-triazine core.It is found that,compa red with the commo nly-used tert-butyl groups,the use of n-butoxy encapsulation groups can lead to smallersinglet-triplet energy gap for the dendrimers,producing stronger TADF effect together with faster reverse intersystem crossing process.Solution-processed TADF organic light-emitting diodes(OLEDs) utilizingalkoxy-encapsulated dendrimers O-D1 and O-D2 as emitters exhibitstate-of-the-art device efficiency withthe maximum external quantum efficiency up to 16.8% and 20.6%,respectively,which are ~1.6 and~2.0 times that of the tert-butyl-encapsulated counterparts.These results suggest that alkoxy encapsulation of the carbazole-based TADF dendrimers can be a promising approach for developing highly efficient emitters for solution-processed OLEDs.

Self-host yellow iridium dendrimers based on carbazole dendrons: synthesis, characterization and application in solution-processed organic light-emitting diodes

On the basis of different generation carbazole dendrons, a series of self-host yellow Ir dendrimers(Y-G0, Y-G1 and Y-G2)have been successfully synthesized and characterized in detail. It is found that the peripheral dendrons can effectively reduce the intermolecular interactions between emissive Ir cores, as verified by the increased photoluminescence quantum yields and film lifetimes. Among these dendrimers, Y-G2 bearing the second generation dendrons shows the best non-doped device performance,revealing a peak luminous efficiency of 20.2 cd/A. The value is nearly twice that of Y-G0 without any dendrons,which could be further improved to 32.1 cd/A by dispersing Y-G2 into a host matrix. We believe that this work will shed light on the development of highly efficient yellow phosphorescent dendrimers with a self-host strategy.

Novel boron-and sulfur-doped polycyclic aromatic hydrocarbon as multiple resonance emitter for ultrapure blue thermally activated delayed fluorescence polymers

Boron(B)-and sulfur(S)-doped polycyclic aromatic hydrocarbons(PAHs)are developed as a novel kind of multiple resonance emitters for ultrapure blue thermally activated delayed fluorescence(TADF)polymers with narrowband electroluminescence.The combination of electron-deficient B atom and electron-rich S atom in PAH can form an intramolecular push-pull electronic system in a rigid aromatic framework,leading to reduced singlet-triplet energy splitting and limited structure relaxation of excited states.The critical roles of S atom in determining emission properties with respect to the oxygen analogues are in two aspects:(i)reducing energy bandgap to shift emission from human-eye-insensitive ultraviolet zone to blue region,and(ii)promoting reverse intersystem crossing process by heavy-atom effect to activate TADF effect.The resulting polymer containing B,S-doped PAH as emitter and acridan as host exhibits efficient blue electroluminescence at 458 nm with small full-width at halfmaximum of 31 nm,representing the first example for ultrapure TADF polymer with narrowband electroluminescence.

Boron-, Sulfur- and Nitrogen-Doped Tridecacyclic Aromatic Emitters with Multiple Resonance Effect for Narrowband Red Emission

Two novel boron(B),sulfur(S),nitrogen(N)-doped polycyclic aromatic hydrocarbon multiple resonance emitters(DBNS and DBNS-tBu)are designed and synthesized for narrowband red emission by embedding two pairs of S and N atoms and two B atoms in para-positions of central benzene rings within a tridecacyclic aromatic skeleton to form donor-π-donor(D-π-D)and acceptor-π-acceptor(A-π-A)structures,which not only exhibit emission maximum at 641 nm with small full width at half maximum of 39 nm,but also combine high photoluminescent quantum efficiency(85%)and rapid reverse intersystem crossing(kRISC=2.2×10^(5) s^(−1)).

Through-space charge transfer polymers for solution-processed organic light-emitting diodes

Through-space charge transfer(TSCT)polymers are an attractive class of luminescent polymers with spatial donor/acceptor architecture and thermally activated delayed fluorescence effect,different from conventional luminescent polymers with conjugated donor-acceptor structure and through-bond charge transfer emission.Their emission comes from the intramolecular charge transfer by through-space pathway because the donor and acceptor segments are spatially proximate to each other in each repeating unit but are physically separated by nonconjugated polymer backbone.In this review,recent advances in TSCT polymers with linear,bottlebrush,and dendritic architectures are presented,with the focus on their molecular design,photophysical behavior,and device performance.We hope that this review shall provide a useful insight of new luminescent polymers with TSCT effect for use in solution-processed organic light-emitting diodes.