Metal halide perovskite nanocrystals (PeNCs) are emerging as one of the most promising materials for optoelectrical devices such as light‐emitting diode (LED) owing to their tunable band gaps, high color purity, and tolerance to defects. Nevertheless, the materials have not yet demonstrated their full potential in practical applications due to the poor stability of PeNCs and their unsatisfactory performance in devices. In this research, LED devices based on CsPbBr₃ NCs are successfully demonstrated as an active light‐emitting layer with enhanced efficiency via potassium doping. The study of the effect of potassium dopant on physicochemical properties of inorganic CsPbBr₃ PeNCs shows that potassium cations (K⁺) remain in the crystal structure of perovskite compound as interstitial defects, which results in better coverage of surface ligands on the PeNCs and improved energy band alignment with adjacent electron injection layer (2,2′,2′‐(1,3,5‐benzinetriyl)‐tris(1‐phenyl‐1‐H‐benzimidazole)) and hole injection layer (poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate) in an LED. As a consequence, the green LED with the K‐doped CsPbBr₃ PeNCs shows luminance up to 5759 cd m^‐2 and external quantum efficiency (EQE) of 5.6%, which is superior to the pristine device without K‐doping (luminance: 4579 cd m^‐2, EQE: 4.8%).

中文翻译：

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钾掺杂增强基于CsPbBr3钙钛矿纳米晶体的发光二极管的绿色发光

金属卤化物钙钛矿纳米晶体（PeNCs）由于其带隙可调，高色纯度和对缺陷的耐受性而成为光电器件（例如发光二极管（LED））中最有希望的材料之一。但是，由于PeNC的稳定性差以及其在设备中的性能不理想，该材料尚未在实际应用中展现出全部潜力。在这项研究中，基于CsPbBr ₃ NC的LED器件被成功地证明是一种有源发光层，通过钾掺杂提高了效率。对钾掺杂对无机CsPbBr ₃ PeNCs的理化性质的影响的研究表明，钾阳离子（K ⁺）作为间隙缺陷保留在钙钛矿化合物的晶体结构中，从而导致PeNC上更好的覆盖表面配体，并改善了与相邻电子注入层的能带排列（2,2'，2'-（1,3,5- LED中的苯并三基）-三（1-苯基-1- H-苯并咪唑）和空穴注入层（聚（3,4-乙二氧基噻吩）聚苯乙烯磺酸盐）。结果，带有K掺杂的CsPbBr ₃ PeNC的绿色LED的亮度高达5759 cd m ^-2，外部量子效率（EQE）为5.6％，优于没有K掺杂的原始器件（亮度：4579） cd m ^-2，EQE：4.8％）。