新型近紅外波段熱激活化延遲螢光材料之物理特性及元件研究

Abstract

有機發光二極體（organic light-emitting diode, OLED）因具備各項優點，已成為重要顯示與照明技術。熱激活化延遲螢光（thermally activated delayed fluorescence, TADF）材料因可有效利用所有激子、理論上可達到100%內部量子效率（internal quantum efficiency, IQE），已成為重要的OLED材料系統。TADF已在可見光波段展現成果，但應用於紅光與近紅外光仍面臨小能階差設計、發光強度與穩定性兼顧等挑戰，仍是目前OLED領域的重要研究方向。 本論文針對近紅外TADF材料 TPA-DPyIs 進行系統性分析，探討其光物理性質及在OLED元件中的應用潛力。透過將TPA-DPyIs摻雜於CBP與mCPCN主體材料中製成薄膜，觀察其光致發光（photoluminescence, PL）與水平發光偶極比(horizontal dipole ratio,θ_(//))。結果顯示，摻雜濃度提升至50 wt.%，PL波長可紅移至673 nm (CBP)及686 nm (mCPCN)。 OLED元件實驗中，以CBP為主體、50 wt.%摻雜時，獲得外部量子效率(external quantum efficiency, EQE)為0.362%；而mCPCN主體元件在相似條件下則展現更紅的電致發光(electroluminescence, EL)頻譜波長（694.2 nm），但效率略低（EQE = 0.237%）。純TPA-DPyIs元件則可實現780 nm以上的近紅外發光，證明其作為近紅外光TADF材料的潛力。然而，整體EQE仍偏低，顯示材料的PLQY與TADF效率仍有提升空間。 本研究探討TPA-DPyIs於長波長近紅外OLED元件的特性，未來可藉由分子設計與元件結構優化以進一步提升效率。 關鍵字: 有機發光二極體、近紅外光、熱活化延遲螢光、外部量子效率

Organic light-emitting diodes (OLEDs) have become an important technology for next-generation displays and lighting, owing to their various advantages.Thermally activated delayed fluorescence (TADF) materials have attracted increasing attention due to their ability to harvest all excitons and achieve a theoretical internal quantum efficiency (IQE) of 100%. Although TADF materials have shown promising results in the visible range, their application and NIR regions remains limited by the difficulty of achieving small ΔEST values while maintaining high photoluminescence intensity. This study focuses on the systematic analysis of a NIR TADF emitter, TPA-DPyIs, including its photophysical properties and device performance in OLEDs. TPA-DPyIs was doped into CBP and mCPCN host materials to fabricate emissive thin films. Photoluminescence (PL) and horizontal dipole orientation ratio (θ//) were examined. The results indicate that increasing the doping concentration to 50 wt.% led to significant redshifts in PL wavelengths to 673 nm (CBP) and 686 nm (mCPCN). In OLED devices, the structure using CBP as the host, 50 wt.% doping concentration, achieved the external quantum efficiency (EQE) of 0.362%. On the other hand, devices using mCPCN as the host exhibited a redder electroluminescence (EL) peak at 694.2 nm but slightly lower efficiency (EQE = 0.237%). Furthermore, undoped TPA-DPyIs devices demonstrated EL emission beyond 780 nm, confirming the material’s potential as a NIR TADF emitter. However, the overall EQE remains relatively low, indicating room for improvement in PL quantum yield and TADF efficiency. This work studies the characteristics of TPA-DPyIs for long-wavelength NIR OLEDs. Future efforts on molecular design and device engineering are needed to further enhance performance and expand its applications. Keywords: organic light-emitting diode, near-infrared, thermally activated delayed fluorescence, external quantum efficiency