The recombination of charges is an important process in organic photonic devices, because the process influences the device characteristics such as the driving voltage, efficiency, and lifetime. Here, by using various homoleptic and heteroleptic Ir complexes as dopants, it is reported that the stationary dipole moment (μ₀) of the dopant rather than the trap depth (ΔE_t) is a major factor determining the recombination mechanism in dye‐doped organic light‐emitting diodes (OLEDs). Dopants with large μ₀ (e.g., homoleptic Ir(III) dyes) induce large charge trapping on them, resulting in high driving voltage and trap‐assisted recombination‐dominated emission. On the other hand, dyes with small μ₀ (e.g., heteroleptic Ir(III) dyes) show Langevin recombination‐dominated emission characteristics with much less charge trapping on them no matter what ΔE_t is, leading to lower driving voltage and higher efficiencies. This finding will be useful in any organic photonic devices such as phosphorescent or thermally assisted delayed fluorescent dye sensitized fluorescent OLEDs where trapping and recombination mechanisms play key roles.

中文翻译：

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揭示掺杂剂极性在有机发光二极管的复合和性能中的作用

电荷的重组是有机光子器件中的重要过程，因为该过程会影响器件的特性，例如驱动电压，效率和寿命。在这里，通过使用各种均配型和杂铱络合物作为掺杂剂，据报道，在固定的偶极矩（μ ₀中的掺杂剂，而不是陷阱深度（Δ的）ë_吨）是确定染料掺杂的重组机制的一个主要因素有机发光二极管（OLED）。与大μ掺杂剂₀（例如，均配型的Ir（III）染料）诱导对他们大电荷俘获，从而导致高的驱动电压和陷阱辅助重组为主的发射。在另一方面，染料与小μ ₀（例如，杂合Ir（III）染料）具有Langevin重组为主的发射特性，无论ΔE _t是多少，它们上的电荷陷阱都少得多，从而导致较低的驱动电压和较高的效率。这一发现将在任何有机光子器件中发挥作用，例如磷光或热辅助延迟荧光染料敏化的荧光OLED，其中俘获和重组机制起着关键作用。