强发光四齿钯 (II)-TADF 发射体。外部量子效率超过 23% 的蓝色 TADF 和 TADF 敏化 OLED,Advanced Optical Materials

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强发光四齿钯 (II)-TADF 发射体。外部量子效率超过 23% 的蓝色 TADF 和 TADF 敏化 OLED
Advanced Optical Materials ( IF 8.0 ) Pub Date : 2023-12-13 , DOI: 10.1002/adom.202302308
Man‐Ki Sit ₁ , Glenna So Ming Tong _{1,

2} , Tsz‐Lung Lam _{1,

2} , Gang Cheng _{1,

2,

3} , Faan‐Fung Hung _{1,

2} , Kwok‐Ming So ₁ , Lili Du _{1,

4} , Kin‐On Choy ₂ , Kam‐Hung Low ₁ , Chi‐Ming Che _{1,

2,

3}

Affiliation

由于Pd(4d)轨道较低，发光钯(II)配合物通常表现出³ IL磷光（IL =配体内），激发态寿命在数百微秒范围内，这限制了它们在蓝色有机光中的应用。发光二极管（OLED）。本文提出了一种分子设计策略，用于开发具有快速辐射衰减率常数和反向系间窜越率 ( k _RISC ) 常数的强发光 Pd(II) 基热激活延迟荧光 (TADF) 发射器。合成的四齿 [Pd(N*C*C^N)] TADF 发射体显示天蓝色到黄色（λ _max = 484–565 nm）发射，激发态寿命在 0.9−8.7 µs 范围内，具有高光致发光量子产率在CH ₂ Cl ₂溶液中高达77% 。在 5 wt.% 2,8-双(二苯基磷酰基)二苯并[b,d]呋喃 (PPF) 薄膜中，这些 [Pd(N*C*C^N)] TADF 配合物显示蓝色到天蓝色 (476− 496 nm）发射，量子产率接近1。变温发射寿命测量、飞秒时间分辨光谱以及密度泛函理论 (DFT) 和瞬态 DFT (TDDFT) 计算共同揭示了这些 [Pd(N*C*C^N)] 的超快k _RISC速率常数TADF 发射器。使用这些 Pd(II)-TADF 发射体作为掺杂剂，效率滚降较小的天蓝色 TADF 和蓝色 TADF 敏化 OLED 分别实现了 24.8% 和 23.1% 的最大外量子效率 (EQE)。

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Strongly Luminescent Tetradentate Palladium(II)-TADF Emitters. Blue TADF And TADF-Sensitized OLEDs with External Quantum Efficiencies Over 23%

Due to the low-lying Pd(4d)-orbitals, luminescent palladium(II) complexes usually show ³IL phosphorescence (IL = intraligand) with excited state lifetimes in the range of hundreds of microseconds, which limits their application in blue organic light-emitting diodes (OLEDs). Here, a molecular design strategy for the development of strongly luminescent Pd(II)-based thermally activated delayed fluorescence (TADF) emitters with fast radiative decay rate constants and reverse intersystem crossing rate (k_RISC) constants is presented. The synthesized tetradentate [Pd(N*C*C^N)] TADF emitters show sky-blue to yellow (λ_max = 484–565 nm) emission with excited state lifetimes in the range of 0.9−8.7 µs and high photoluminescence quantum yield of up to 77% in CH₂Cl₂ solution. In 5 wt.% 2,8-bis(diphenylphosphoryl)dibenzo[b,d]furan (PPF) thin films, these [Pd(N*C*C^N)] TADF complexes display blue to sky-blue (476−496 nm) emission with quantum yields close to unity. Variable-temperature emission lifetime measurements, femtosecond time-resolved spectroscopy, and density functional theory (DFT) and time-dependent DFT (TDDFT) calculations together reveal ultrafast k_RISC rate constants of these [Pd(N*C*C^N)] TADF emitters. Using these Pd(II)-TADF emitters as dopants, sky-blue TADF and blue TADF-sensitized OLEDs with small efficiency roll-offs achieved high maximum external quantum efficiencies (EQEs) of 24.8% and 23.1%, respectively.

更新日期：2023-12-13

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