Introducing molecular chirality into perovskite crystal structures has enabled the control of carrier spin states, giving rise to circularly polarized luminescence (CPL) in thin films and circularly polarized electroluminescence (CPEL) in LEDs. Spin-LEDs can be fabricated either through a spin-filtering layer enabled by chiral-induced spin selectivity or a chiral emissive layer. The former requires a high degree of spin polarization and a compatible spinterface for efficient spin injection, which might not be easily integrated into LEDs. Alternatively, a chiral emissive layer can also generate circularly polarized electroluminescence, but the efficiency remains low and the fundamental mechanism is elusive. In this work, we report an efficient green LED based on quasi-two-dimensional (quasi-2D) chiral perovskites as the emitting layer (EML), where CPEL is directly produced without separate carrier spin injection. The optimized chiral perovskite thin films exhibited strong CPL at 535 nm with a photoluminescence quantum yield (PLQY) of 91% and a photoluminescence dissymmetry factor (g_lum) of 8.6 × 10^–2. Efficient green spin-LEDs were successfully demonstrated, with a large EL dissymmetry factor (g_EL) of 7.8 × 10^–2 and a maximum external quantum efficiency (EQE) of 13.5% at room temperature. Ultrafast transient absorption (TA) spectroscopic study shows that the CPEL is generated from a rapid energy transfer accompanied by spin transfer from 2D to 3D perovskites. Our study not only demonstrates a reliable approach to achieve high performance spin-LEDs but also reveals the fundamental mechanism of CPEL with an emissive layer of chiral perovskites.

中文翻译：

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通过手性钙钛矿中的超快能量和自旋漏斗实现高效绿色自旋发光二极管


将分子手性引入钙钛矿晶体结构中可以控制载流子自旋态，从而产生薄膜中的圆偏振发光（CPL）和LED中的圆偏振电致发光（CPEL）。自旋 LED 可以通过手性诱导自旋选择性实现的自旋过滤层或手性发射层来制造。前者需要高度的自旋极化和兼容的自旋界面以实现高效的自旋注入，这可能不容易集成到 LED 中。另外，手性发射层也可以产生圆偏振电致发光，但效率仍然很低，而且基本机制难以捉摸。在这项工作中，我们报告了一种基于准二维（准2D）手性钙钛矿作为发光层（EML）的高效绿色LED，其中CPEL是直接产生的，无需单独的载流子自旋注入。优化后的手性钙钛矿薄膜在535 nm处表现出强CPL，光致发光量子产率（PLQY）为91%，光致发光不对称因子（g _lum ）为8.6 × 10 ^–2 。成功展示了高效的绿色自旋 LED，其 EL 不对称因子 (g _EL ) 为 7.8 × 10 ^–2 ，最大外量子效率 (EQE) 在室温下为 13.5%温度。超快瞬态吸收（TA）光谱研究表明，CPEL 是由快速能量转移产生的，伴随着从 2D 到 3D 钙钛矿的自旋转移。我们的研究不仅展示了实现高性能自旋 LED 的可靠方法，而且揭示了具有手性钙钛矿发射层的 CPEL 的基本机制。