Recently, perovskites have attracted intense attention due to their high potential in optoelectronic applications. Employing perovskites as the emissive materials of lightemitting electrochemical cells (LECs) shows the advantages of simple fabrication process, low-voltage operation, and compatibility with inert electrodes, along with saturated electroluminescence (EL) emission. Unlike in previously reported perovskite LECs, in which salts are incorporated in the emissive layer, the ion-transport layer was separated from the emissive layer in this work. The layer of ionic transition metal complex (iTMC) not only provides mobile ions but also serves as an electron-injection/transport layer. Orthogonal solvents are used in spin coating to prevent the intermixing of stacked perovskite and iTMC layers. The blue iTMC with high ionization potential is effective in blocking holes from the emissive layer and thus ensures EL color saturation. In addition, the carrier balance of the perovskite/iTMC LECs can be optimized by adjusting the iTMC layer thickness. The optimized external quantum efficiency of the CsPbBr 3 /iTMC LEC reaches 6.8 %, which is among the highest reported values for perovskite LECs. This work successfully demonstrates that, compared with mixing all components in a single emissive layer, separating the layer of ion transport, electron injection and transport from the perovskite emissive layer is more effective in adjusting device carrier balance. As such, solution-processable perovskite/iTMC LECs open up a new way to realize efficient perovskite LECs.

Solid-state light-emitting electrochemical cells (LECs) show promising advantages of simple device architecture, low operation voltage, and insensitivity to the electrode work functions such that they have high potential in low-cost display and lighting applications. In this work, novel white LECs based on phosphor-sensitized thermally activated delayed fluorescence (TADF) are proposed. The emissive layer of these white LECs is composed of a blue-green phosphorescent host doped with a deep-red TADF guest. Efficient singlet-to-triplet intersystem crossing (ISC) on the phosphorescent host and the subsequent Förster energy transfer from the host triplet excitons to guest singlet excitons can make use of both singlet and triplet excitons on the host. With the good spectral overlap between the host emission and the guest absorption, 0.075 wt.% guest doping is sufficient to cause substantial energy transfer efficiency (ca. 40 %). In addition, such a low guest concentration also reduces the self-quenching effect and a high photoluminescence quantum yield of up to 84 % ensures high device efficiency. The phosphor-sensitized TADF white LECs indeed show a high external quantum efficiency of 9.6 %, which is comparable with all-phosphorescent white LECs. By employing diffusive substrates to extract the light trapped in the substrate, the device efficiency can be further improved by ca. 50 %. In the meantime, the intrinsic EL spectrum and device lifetime of the white LECs recover since the microcavity effect is destroyed. This work successfully demonstrates that the phosphor-sensitized TADF white LECs are potential candidates for efficient white light-emitting devices.

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In order to investigate the filterability of artificial fiber, salts were added to the fiber for particulate removal. In addition, nanofibers were prepared for particle filtration efficiency assessment, and Nylon 6 nanofibers were prepared by electrospinning. Scanning electron microscopy (SEM) was used for analyzing the fiber characteristics. Furthermore, the single-factor experimental method was used to study the optimal material preparation method and operating parameters, including content of different salts (NaCl and KCl), with Nylon 6 nanofibers for particle removal. The particle removal efficiency of pure Nylon 6 nanofibers was about 95%. The removal efficiencies of Nylon 6 nanofibers containing NaCl and KCl were 99% and 98%, respectively. It was found that the removal efficiency of nanofibers was decreased with increasing content of salts in Nylon 6 nanofibers.

A layer of ionic transition metal complex promotes electron injection and transport, resulting in an improved carrier balance of green CsPbBr3 perovskite/iTMC light‐emitting electrochemical cells (LECs). The optimized external quantum efficiency reaches 6.8 %, which is among the highest values reported for perovskite LECs so far. More information can be found in the Research Article by C.‐W. Lu, Z.‐P. Yang, H.‐C. Su, et al. (DOI: 10.1002/chem.202103739).