Wang Haoran, Dou Yongjiang, Shen Piaoyang, Kong Lingmei, Yuan Hao, Luo Yun, Zhang Xiaoyu, Yang Xuyong
Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, 149 Yanchang Road, Shanghai, 200072, China.
College of Materials Science and Engineering, Jilin University, Changchun, 130012, China.
Small. 2020 May;16(20):e2001062. doi: 10.1002/smll.202001062. Epub 2020 Apr 20.
Color-saturated red light-emitting diodes (LEDs) with emission wavelengths at around 620-640 nm are an essential part of high-definition displays. Metal halide perovskites with very narrow emission linewidth are promising emitters, and rapid progress has been made in perovskite-based LEDs (PeLEDs); however, the efficiency of the current color-pure red PeLEDs-still far lags behind those of other-colored ones. Here, a simple but efficient strategy is reported to gradually down-shift the Fermi level of perovskite nanocrystals (NCs) by controlling the interaction between NCs and their surface molecular electron acceptor-benzyl iodide with aromatic rings-and realize p-doping in the color-saturated 625 nm emitting NCs, which significantly reduces the hole injection barrier in devices. Besides, both the luminescence efficiency and electric conductivity of perovskite NCs are enhanced as additional advantages as the result of surface defects passivation. As a result, the external quantum efficiency for the resulting LED is increased from 4.5% to 12.9% after benzyl iodide treatment, making this device the best-performing color-saturated red PeLED so far. It is further found that the hole injection plays a more critical role than the photoluminescence efficiency of perovskite emitter in determining the LED performance, which implies design principles for efficient thin-film planar LEDs.
发射波长在620 - 640纳米左右的色彩饱和红色发光二极管（LED）是高清显示器的重要组成部分。发射线宽非常窄的金属卤化物钙钛矿是很有前景的发光体，基于钙钛矿的发光二极管（PeLED）已取得快速进展；然而，目前纯红色PeLED的效率仍远远落后于其他颜色的PeLED。在此，报道了一种简单而有效的策略，即通过控制钙钛矿纳米晶体（NCs）与其表面分子电子受体——带有芳香环的苄基碘之间的相互作用，逐步降低钙钛矿纳米晶体的费米能级，并在发射625纳米色彩饱和光的纳米晶体中实现p型掺杂，这显著降低了器件中的空穴注入势垒。此外，作为表面缺陷钝化的额外好处，钙钛矿纳米晶体的发光效率和电导率都得到了提高。结果，经苄基碘处理后，所得发光二极管的外量子效率从4.5%提高到了12.9%，使该器件成为迄今为止性能最佳的色彩饱和红色PeLED。进一步发现，在决定发光二极管性能方面，空穴注入比钙钛矿发光体的光致发光效率起着更关键的作用，这暗示了高效薄膜平面发光二极管的设计原则。
