Dual Passivation of Perovskite Defects for Light‐Emitting Diodes with External Quantum Efficiency Exceeding 20%,Advanced Functional Materials

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Dual Passivation of Perovskite Defects for Light‐Emitting Diodes with External Quantum Efficiency Exceeding 20%
Advanced Functional Materials ( IF 18.5 ) Pub Date : 2020-02-05 , DOI: 10.1002/adfm.201909754
Zhibin Fang ₁ , Wenjing Chen ₁ , Yongliang Shi ₁ , Jin Zhao ₁ , Shenglong Chu ₁ , Ji Zhang ₁ , Zhengguo Xiao ₁

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Solution‐processed metal halide perovskites (MHPs) have attracted much attention for applications in light‐emitting diodes (LEDs) due to their wide color gamut, high color purity, tunable emission wavelength, balanced electron/hole transportation, etc. Although MHPs are very tolerant to defects, the defects in solution‐processed perovskite LEDs (PeLEDs) still cause severe nonradiative recombination and device instability. Here, molecular design of additives for dual passivation of both lead and halide defects in perovskites is reported. A bi‐functional additive, 4‐fluorophenylmethylammonium‐trifluoroacetate (FPMATFA), is synthesized by using a simple solution process. The TFA anions and FPMA cations can bond with undercoordinated lead and halide ions, respectively, resulting in dual passivation of both lead and halide defects. In addition, the bulky FPMA group can constrain the grain growth of 3D perovskite, enhancing electron–hole capture rates and radiative recombination rates. As a result, high‐performance PeLEDs with a peak external quantum efficiency reaching 20.9% and emission wavelength at 694 nm are achieved using formamidinium‐cesium lead iodide‐bromide (FA_0.33Cs_0.67Pb(I_0.7Br_0.3)₃). Furthermore, the operational lifetime of PeLEDs is also greatly improved due to the low trap density in the perovskite film.

中文翻译：

外部量子效率超过20％的发光二极管的钙钛矿缺陷双钝化

固溶处理的金属卤化物钙钛矿（MHP）色域宽，色纯度高，发射波长可调，电子/空穴传输平衡等，因此在发光二极管（LED）中的应用引起了广泛关注。尽管MHP非常耐受缺陷，固溶钙钛矿LED（PeLED）中的缺陷仍然会导致严重的非辐射重组和器件不稳定。在此，报道了钙钛矿中铅和卤化物缺陷双重钝化的添加剂分子设计。通过使用简单的溶液法合成了双功能添加剂4-氟苯基甲基三氟乙酸铵（FPMATFA）。TFA阴离子和FPMA阳离子可以分别与配位不足的铅和卤化物离子键合，从而导致铅和卤化物缺陷双重钝化。此外，庞大的FPMA组可以限制3D钙钛矿的晶粒长大，从而提高电子-空穴捕获率和辐射复合率。结果，使用甲ami铯碘化铅-溴化物（FA）实现了峰值外部量子效率达到20.9％且发射波长为694 nm的高性能PeLED。_0.33 Cs _0.67 Pb（I _0.7 Br _0.3）₃）。此外，由于钙钛矿膜中的陷阱密度低，因此PeLED的使用寿命也大大提高。

更新日期：2020-03-19

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