Chemical passivation via functional additives plays a critical role in achieving high performance perovskite light‐emitting diodes (PeLEDs). Here, perovskite composite films for high performance PeLEDs by using zwitterion 3‐aminopropanesulfonic acid (APS) as the additive are developed. The sulfonic group of APS can simultaneously passivate deep and shallow level defects in perovskites via coordinate and hydrogen bonding, which leads to suppressed non‐radiative recombination and ion migration in the perovskite composite films. Based on this, PeLEDs with a peak external quantum efficiency of 19.2% and a half‐lifetime of 43 h at a constant current density of 100 mA cm−2 are obtained, representing one of the most stable and efficient PeLEDs under high current densities.
Metallic powders with various thermodynamic stability oxide films (Ag, Cu, and Al powders) were sintered using a pulse electric-current sintering (PECS) process. Behavior of oxide films at powder surfaces and their effect on the sintering properties were investigated. The results showed that the sintering properties of metallic powders in the PECS process were subject to the thermodynamic stability of oxide films at particles surfaces. The oxide films at Ag powder surfaces are decomposed during sintering with the contact region between the particles being metal/metal bond. The oxide films at Cu powder surfaces are mainly broken via loading pressure at a low sintering temperature. At a high sintering temperature, they are mainly dissolved in the parent metal, and the contact regions turn into the direct metal/metal bonding. Excellent sintering properties can be received. The oxide films at Al powder surfaces are very stable, and cannot be decomposed and dissolved, but broken by plastic deformation of particles under loading pressure at experimental temperatures. The interface between particles is partially bonded via the direct metal/metal bonding making it difficult to achieve good sintered properties.
The effect of surface asperity (mainly ridge height H, ridge wavelength W and aspect ratio H=W) on the diffusion bonding process was investigated. Ridge wavelength W as well as ridge height H have a significant effect on the properties of the diffusion bonded joint. The percent of bonded area increased with decreases in W and H. When the ridge height H was constant, an increase in aspect ratio H=W accelerated atomic diffusion at void surfaces and bonding interfaces, facilitated void shrinking and increased the bonded area. This can improve the strength of diffusion bonded joints. The percent of bonded area can be predicted by numerical analysis for surfaces prepared by lathe machining.
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