The Study on the Relationship between Dynamic Balance Energy Distribution and Spectral Stability with Voltage Change in White Organic Light Emitting Diode

The stable spectrum can be obtained when the voltage changes, which is a necessary condition for the white organic light emitting diode (WOLED) device to be widely used in the field of solid-state lighting. However, with the increase of voltage, the movement of the recombination zone (RZ) is inevitable because the perfect bipolar host material is difficult to obtain, which will redistribute the energy in the light emitting layer (EML) and affect the stability of the spectrum. We fabricate a series of ternary hybrid WOLEDs with a simple structure by inserting ultra-thin PO-T2T into the blue exciplex (TCTA:TPBi) to form the green interface exciplex. Without considering the movement of RZ, device B2 realizes the dynamic balance energy distribution in EML and stable spectrum by controlling two processes of the Dexter energy transfer and exciton capture. By modifying the doping ratio of the host material, we also find that the broadened RZ is helpful to further improve the spectral stability of the device. When the voltage changes from 3 V to 7 V, the change range of color coordinates is only (0.026, 0.025).

The spectrum and stability of travelling pulses in a coupled FitzHugh-Nagumo equation

For a coupled slow-fast FitzHugh-Nagumo(FHN)equation derived from a reaction-diffusionmechanics(RDM)model,Holzer et al.(2013)studied the existence and stability of the travelling pulse,which consists of two fast orbit arcs and two slow ones,where one fast segment passes the unique fold point with algebraic decreasing and two slow ones follow normally hyperbolic critical curve segments.Shen and Zhang(2021)obtained the existence of the travelling pulse,whose two fast orbit arcs both exponentially decrease,and one of the slow orbit arcs could be normally hyperbolic or not at the origin.Here,we characterize both the nonlinear and spectral stability of this travelling pulse.

A dual-blue light-emitting diode based on strain-compensated InGaN-AlGaN/GaN quantum wells

A strain-compensated InGaN quantum well（QW） active region employing a tensile AlGaN barrier is analyzed.Its spectral stability and efficiency droop for a dual-blue light-emitting diode（LED） are improved compared with those of the conventional InGaN/GaN QW dual-blue LEDs based on a stacking structure of two In0.18Ga0.82N/GaN QWs and two In0.12Ga0.88N/GaN QWs on the same sapphire substrate.It is found that the optimal performance is achieved when the Al composition of the strain-compensated AlGaN layer is 0.12 in blue QW and 0.21 in blue-violet QW.The improvement performance can be attributed to the strain-compensated InGaN-AlGaN/GaN QW,which can provide a better carrier confinement and effectively reduce leakage current.

Acid-etching induced metal cation competitive lattice occupancy of perovskite quantum dots for efficient pure-blue QLEDs

Low efficiency and spectral instability caused by the surface defects have been considerable issues for the mixed-halogen blue emitting perovskite quantum dots light-emitting diodes(PeQLEDs).Here,an in situ surface passivation to perovskite quantum dots(PeQDs)is realized by introducing the metal cations competitive lattice occupancy assisted with acid-etching,in which the longchain,insulating and weakly bond surface ligands are removed by addition of octanoic acid(OTAC).Meanwhile,the dissolved A-site cations(Na^(+))compete with the protonated oleyl amine and are subsequently anchored to the surface vacancies.The preadded lead bromide,acting as inorganic ligands,demonstrates strong bonding to the uncoordinated surface ions.The as-synthesized PeQDs show the boosted photoluminescence quantum yield(PLQY)and superior stability with longer lifetime.As a result,the PeQLEDs(470 nm)based on the OTAC-Na PeQDs exhibit an external quantum efficiency of 8.42%in the mixed halogen PeQDs(CsPb(Br_(x)Cl_(1−x))_(3)).Moreover,the device exhibits superior spectra stability with negligible shift.Our competition mechanism in combination with in situ passivation strategy paves a new way for improving the performance of blue PeQLEDs.

Stability/Instability of Solitary waves with Nonzero Asymptotic Value for a PDE in Microstructural Solid Materials

The present paper deals with results of stability/instability of solitary waves with nonzero asymptotic value for a microstructure PDE. By the exact solitary wave solutions and detailed computations, we set up the explicit expression for the discrimination d′′（c）. Finally, a complete study of orbital stablity/instablity for the explicit exact solutions is given.