Perovskite light‐emitting diodes (PeLEDs) are emerging candidates for the applications of solution‐processed full‐color displays. However, the device performance of deep‐blue PeLED still lags far behind that of their red and green counterparts, which is largely limited by low external quantum efficiency (EQE) and poor operational stability. Here, a facile and reliable crystallization strategy for perovskite grains is proposed, with improved deep‐blue emission through rational interfacial engineering. By modifying the substrate with potassium cation (K+) as the supplier of heterogeneous nucleation seeds, the interfacial K+‐guided grain growth is realized for well‐packed perovskite assemblies with high surface coverage and the controlled crystal orientation, leading to the enhanced radiative recombination and hole‐transport capabilities. Synergistical boost in device performance is achieved for deep‐blue PeLEDs emitting at 469 nm with a peak EQE of 4.14%, a maximum luminance of 451 cd m–2, and spectrally stable color coordinates of (0.125, 0.076) that matches well with the National Television System Committee (NTSC) standard blue.

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Herein a new type of 2D/0D/2D face-to-face contact g-C 3 N 4 @Au@Bi 4 Ti 3 O 12 heterojunction photocatalysts have been developed. The ternary composite photocatalysts are constructed by coupling Bi 4 Ti 3 O 12 nanosheets with g-C 3 N 4 nanosheets face-to-face and sandwiching Au nanoparticles between Bi 4 Ti 3 O 12 and g-C 3 N 4 nanosheets. The as-prepared g-C 3 N 4 @Au@Bi 4 Ti 3 O 12 composite photocatalysts were systematically investigated by various characterization techniques including XRD, UV-vis DRS, FTIR, SEM, TEM and XPS. The degradation experiments were carried out by removing rhodamine B (RhB) from water under simulated sunlight. It is found that the g-C 3 N 4 @Au@Bi 4 Ti 3 O 12 composite photocatalysts exhibit much enhanced photodegradation performance when compared with bare Bi 4 Ti 3 O 12 and g-C 3 N 4 nanosheets, and moreover they exhibit excellent photocatalytic stability in recycling dye degradation. The underlying photodegradation mechanism of the g-C 3 N 4 @Au@Bi 4 Ti 3 O 12 composite photocatalysts was systematically investigated and discussed.

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Regardless of the rapid advance on perovskite light‐emitting diodes (PeLEDs), the lack of long‐term operational stability hinders the practicality of this technology. Particularly, thermal management is indispensable to control the Joule heating induced by charge transport and parasitic re‐absorption of internally confined photons. Herein, a synergetic device architecture is proposed for minimizing the optical energy losses in PeLEDs toward high efficiency and long lifetime. By adopting a carefully modified perovskite emitter in combination with an improved light outcoupling structure, red PeLEDs emitting at 666 nm achieve a peak external quantum efficiency of 21.2% and an operational half‐lifetime of 4806.7 h for an initial luminance of 100 cd m‐2. The enhanced light extraction from trapped modes can efficiently reduce the driving current and suppress optical energy losses in PeLEDs, which in turn ameliorate the heat‐induced device degradation during operation. This work paves the way toward high‐performance PeLEDs for display and lighting applications in the future.