Seeded Polymerization of an Amide-Functionalized Diketopyrrolopyrrole Dye in Aqueous Media

The self-assembly of an amide-functionalized dithienyldiketopyrrolopyrrole (DPP) dye in aqueous media was achieved through seed-initiated supramolecular polymerization. Temperature- and time-dependent studies showed that the spontaneous polymerization of the DPP derivative was temporally delayed upon cooling the monomer solution in a methanol/water mixture. Theoretical calculations revealed that an amide-functionalized DPP derivative adopts an energetically favorable folded conformation in the presence of water molecules due to hydration. This conformational change is most likely responsible for the trapping of monomers in the initial stage of the cooperative supramolecular polymerization in aqueous media. However, the monomeric species can selectively interact with externally added fragmented aggregates as seeds through concerted π-stacking and hydrogen-bonding interactions. Consequently, the time course of the supramolecular polymerization and the morphology of the aggregated state can be controlled, and one-dimensional fibers that exhibit a J-aggregate-like bathochromically shifted absorption band can be obtained.     

Decay rate for viscoelastic wave equation of variable coefficients with delay and dynamic boundary conditions

In this paper, we consider a viscoelastic wave equation of variable coefficients in the presence of past history with nonlinear damping and delay in the internal feedback and dynamic boundary conditions. Under suitable assumptions, we establish an explicit and general decay rate result without imposing restrictive assumption on the behavior of the relaxation function at infinity by Riemannian geometry method and Lyapunov functional method.     

General non local boundary value problem for second order elliptic equation

In this paper we study a class of second order coefficient operators differential equation with general (possibly non local) boundary conditions. We obtain new results extending those given in a previous paper 1 . Existence, uniqueness and optimal regularity of the strict solution are proved in UMD spaces, using the well‐known Dore–Venni theorem.     

基于混合空穴注入层的湿法制备高效蓝光热激活延迟有机发光二极管

在溶液法制备有机电致发光器件(OLEDs)的研究中, PEDOT∶PSS由于具有较好的成膜性与高透光性而常被用作器件的空穴注入层。但相关研究表明, PEDOT∶PSS本身稳定性较差以及功函数较低,这使得溶液法制备OLEDs的性能差且不稳定。蓝色作为全彩色的三基色之一,制备高效的蓝光器件对于实现高质量显示器件和固态照明装置必不可少。而目前溶液法制备蓝光OLEDs的器件效率普遍较差,针对此问题,本文利用传统的蓝光热激活延迟荧光发光(TADF)材料DMAC-DPS作为发光层,用溶液法制备了蓝光TADF OLEDs,通过在PEDOT∶PSS中掺杂PSS-Na制备混合空穴注入层(mix-HIL)来提高空穴注入层的功函数,研究其对于蓝光TADF OLEDs器件性能的影响。首先在PEDOT∶PSS水溶液中掺入不同体积的PSS-Na溶液,在相同条件下旋涂制膜,进行器件制备。通过观测各个实验组器件的电致发光(EL)光谱,发现掺入PSS-Na后器件EL谱存在光谱蓝移的现象,这是由于掺入PSS-Na水溶液后, mix-HIL层的厚度有所降低,使得在微腔效应作用下, EL光谱发生蓝移。通过对比各组器件的电流密度-电压-亮度(J-V-L)曲线及其计算所得器件的电流效率,结果显示随着PSS-Na的掺入,器件的亮度和电流都有所增大,器件的电流效率也得到了提升,当掺杂比例为0.5∶0.5(PEDOT∶PSS/PSS-Na)时提升幅度最大(亮度提升86.7%,电流效率提升34.3%)。通过在瞬态电致发光测试过程中施加或撤去驱动电压观测了器件EL强度的变化,分析了在混合空穴注入层/发光层(mix-HIL/EML)界面处的电荷积累情况。实验证明,通过在PEDOT∶PSS中掺杂PSS-Na制备mix-HIL获得了蓝光TADF OLEDs器件性能的提升,这是一个获得高效率溶液法制备OLEDs的可行方法。