在本研究中我們主要目標為開發高效率的黃色與紅色磷光有機發光二極體 (phosphorescent organic light Emitting diodes，簡稱PhOLED)。我們以不同位置的氰基修飾Bis(2-phenylpyridine)(acetylacetonate)iridium (Ir(ppy)2(acac))，產生三種衍生物即Ir(3-CNpy)、Ir(4-CNpy) 和Ir(10-CNpy)。透過理論計算和單晶結構的分析，發現在ppy配體的不同位置上修飾氰基取代可以調整Ir錯合物的電子雲分佈和配位鍵結長度。因此Ir錯合物的電荷轉移能力增強，使得氰基取代的Ir(ppy)2(acac) 衍生物能隙縮小。三個目標分子的光致發光光譜主峰波長位於黃色至紅色區間 (544 nm至625 nm)。此外Ir(3-CNpy)、Ir(4-CNpy) 和Ir(10-CNpy) 分別表現出83%、54% 和75% 的高PLQY。值得注意的是，採用Ir(3-CNpy) 作為發光體的元件表現出最大外部量子效率 (external quantum efficiency，簡稱EQE) 為25.4%，電流效率 (current efficiency，簡稱CE) 為56.9 cd⸱A-1，功率效率 (power efficiency，簡稱PE) 為68.7 lm⸱W-1，並在8 V時達到最大亮度61,340 cd⸱m-2。該元件的EQE在亮度為1,000和10,000 cd⸱m-2時保持為24.3% 和19.9%，其對應的效率滾降分別為4.3% 和21.7%。與使用具有擴展共軛結構的配體之Ir錯合物相比，我們的結果證明了一種簡單的磷光發光體分子設計策略，並降低Ir錯合物本身的分子量，在黃光至紅光區域實現高效率的PhOLED。

In this study, our main goal was to develop highly efficient yellow and red phosphorescent organic light-emitting diodes phosphorescent organic light-emitting diodes (PhOLEDs). We modified bis(2-phenylpyridine)(acetylacetonate)iridium (Ir(ppy)2(acac)) with cyano groups at different positions to generate three compounds, namely Ir(3-CNpy), Ir(4-CNpy) and Ir(10-CNpy). Through theoretical calculation and single crystal structure analysis, it was found that the electron cloud distribution and coordination bond length of the Ir complex could be adjusted by cyano substitution at different positions of the ppy ligand. Therefore, the charge transfer ability of Ir complexes was enhanced, and the energy gap of cyano-substituted Ir(ppy)2(acac) derivatives was narrowed. The main peak wavelengths of the photoluminescence spectra of the three Ir complexes were located in the yellow to red range (544 nm to 625 nm). Furthermore, Ir(3-CNpy), Ir(4-CNpy) and Ir(10-CNpy) exhibited high PLQY of 83%, 54% and 75%, respectively. Notably, the device using Ir(3-CNpy) as the emitter exhibited a maximum external quantum efficiency (EQE) of 25.4% and a current efficiency (CE) of 56.9 cd⸱A-1. The power efficiency (PE) was 68.7 lm⸱W-1 and reaches a maximum brightness of 61,340 cd⸱m-2 at 8 V. At luminances of 1,000 and 10,000 cd⸱m-2, the device maintains an EQE of 24.3% and 19.9%, corresponding to an efficiency roll-off of 4.3% and 21.7%, respectively. Compared with Ir complexes using ligands with extended conjugated structures, our results demonstrate a simple molecular design strategy for phosphorescent emitters and reduce the molecular weight of the Ir complexes themselves in the yellow to red region, achieving highly efficient PhOLEDs.

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