The perovskite-based optoelectronic applications always suffer from stability issues, due to the intrinsic chemical instability of the perovskite materials. Besides, poly­(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) is always utilized as an anode buffer layer in thin-film perovskite light-emitting diodes (PeLEDs), which may lead to stability issues due to the hygroscopic and acidic nature of PEDOT:PSS. In this paper, inorganic metal oxide NiO x is employed as a hole injection layer (HIL) and hole transport layer (HTL) to substitute detrimental PEDOT:PSS in all-inorganic PeLEDs. Then fully covered CsPbBr3 polycrystalline films are fabricated by using a one-step spin-coating method based on nonstoichiometric and polymer-assisted perovskite precursor solutions. The optimized films not only have compact morphology but also have excellent photoluminescence quantum yield (PLQY). Encouragingly, by introducing a metal oxide NiO x , the CsPbBr3 PeLEDs show a maximum luminance of 23 828 cd m–2 and maximum current efficiency (CE) of 9.54 cd A–1, which lead to a 1.6-fold and 3.3-fold increase compared to the PeLEDs with a PEDOT:PSS HIL. Besides, the inorganic PeLEDs show high color purity with a full-width at half-maximum (fwhm) of only 16 nm. The combination of inorganic NiO x with inorganic perovskite also shows improved operation stability of devices, which paves the way for highly efficient all-inorganic PeLEDs.

At first, a semi-discrete Crank-Nicolson (CN) formulation with respect to time for the non-stationary incompressible Boussinesq equations is presented. Then, a fully discrete stabilized CN mixed finite volume element (SCNMFVE) formulation based on two local Gauss integrals and parameter-free is established directly from the semi-discrete CN formulation with respect to time. Next, the error estimates for the fully discrete SCNMFVE solutions are derived by means of the standard CN mixed finite element method. Finally, some numerical experiments are presented illustrating that the numerical errors are consistent with theoretical results, the computing load for the fully discrete SCNMFVE formulation are far fewer than that for the stabilized mixed finite volume element (SMFVE) formulation with the first time accuracy, and its accumulation of truncation errors in the computational process is far lesser than that of the SMFVE formulation with the first time accuracy. Thus, the advantage of the fully discrete SCNMFVE formulation for the non-stationary incompressible Boussinesq equations is shown sufficiently.

In this article, we devote ourselves to the research of order reduction of natural boundary element (NBE) based on a proper orthogonal decomposition (POD) for the parabolic equation in the two-dimensional (2D) unbounded domain. For this purpose, we first build a NBE format for the parabolic equation in the 2D unbounded domain and discuss the existence, stability, and convergence of the NBE solutions. And then, we build a reduced-order NBE extrapolated (RONBEE) format based on POD, analyze the errors between the classical NBE and RON-BEE solutions, and supply the implementation procedure for the RONBEE format. Finally, we utilize some numerical experiments to validate that the numerical computational consequences are consistent with the theoretical ones such that the effectiveness and feasibility of the RONBEE format are further verified. Keywords Natural boundary element • Proper orthogonal decomposition • Parabolic equation in the two-dimensional unbounded domain • Reduced-order extrapolated natural boundary element method • Error estimate Mathematics Subject Classification 65N38 • 65N30 • 65N15 Communicated by Philippe Heluy.

Abstract:Interfacial materials are essential to the performance and stability of polymer solar cells (PSCs). Herein, solution-processed zirconium(IV) isopropoxide (Zr[OCH(CH 3 ) 2 ] 4 , ZrIPO) has been employed as an efficient cathode buffer layer between the Al cathode and photoactive layer. The ZrIPO buffer layer is prepared simply via spin-coating its isopropanol solution on the photoactive layer at room temperature without any post-treatment. When using ZrIPO/Al instead of the traditionally used Ca/Al cathode in PSCs, the short-circuit current density (J sc ) is significantly improved and the series resistance of the device is decreased. The power conversion efficiency (PCE) of the P3HT:PCBM-based device with ZrIPO buffer layer reaches 4.47% under the illumination of AM1.5G, 100 mW/cm 2 . A better performance with PCE of 8.07% is achieved when a low bandgap polymer PBDTBDD is selected as donor material. The results indicate that ZrIPO is a promising electron collection material as a substitute of the traditional low-work-function cathode for high performance PSCs.