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.

中文翻译：

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界面钾引导晶粒生长，实现高效深蓝色钙钛矿发光二极管

钙钛矿发光二极管（PeLED）是溶液处理全彩显示器应用的新兴候选产品。但是，深蓝色PeLED的设备性能仍然远远落后于红色和绿色PeLED的设备性能，这在很大程度上受到外部量子效率（EQE）低和操作稳定性差的限制。在此，提出了一种钙钛矿晶粒的简便而可靠的结晶策略，并通过合理的界面工程改善了深蓝色发射。通过用钾阳离子（K ⁺）修饰底物作为异质核种的供应商，界面K ⁺对于具有高表面覆盖率和可控晶体取向的，包装良好的钙钛矿组件，可以实现引导下的晶粒长大，从而增强了辐射复合和空穴传输能力。对于深蓝色PeLED，在469 nm处发射时具有协同性能提升，峰值EQE为4.14％，最大亮度为451 cd m ^–2，光谱稳定的颜色坐标为（0.125，0.076），与色标非常匹配。国家电视系统委员会（NTSC）标准为蓝色。