合成與探索熱延遲活化螢光苯並咪唑材料於有機發光二極體之應用

Abstract

我們報告了新的主體材料，用以增強基於多重共振誘導熱活化延遲螢光（MR-TADF）的純深藍色有機發光二極體OLED），進一步縮短發射半峰全寬（FWHM）。基於不尋常的不對稱設計概念，我們合成了兩種新的主體化合物Bz2cb和Bz2cbz。儘管在晶體中具有緻密且剛性的分子堆積，Bz2cbz 透過氣相沉積顯示出非晶像形態，正如掠入射廣角 X 射線散射 (GIWAXS) 分析所證實的那樣。透過將一種有前途的 MR-TADF 發射體 ν-DABNA-O-Me 融入 Bz2cb 和 Bz2cbz 薄膜中，成功展示了高純度的深藍色 OLED。值得注意的是，Bz2cbz元件表現出464 nm電致發光（EL），半高寬為22 nm，伴隨著0-1電子振動邊帶的減少，最大外量子效率（EQEmax）為28.2%，整體上達到了真藍色國際照明委員會座標 (CIE) 為 (0.13, 0.07)，高藍色指數為 253。事實證明，非晶像薄膜的形成是一個以前未被認識到的外部微調 MR-TADF 的重要因素，而導致OLED的色純度較高。 我們在此報導了一種新合成的TADF材料，材料本身於UV光照射下放出白色光線，是由於其單體以及聚集所造成，我們透過分析其瞬態光譜以及其lifetime，可以得知其形成白色光的原理為具有兩種不同的架構，進一步透過TEM分析表明，分子經過結晶，外層的殼以及內層的堆疊形成球體狀結構，透過共軛交顯微鏡可以清楚的表明，外層為藍色，內層為綠色，並將其作成non-doped元件，元件可以顯示出國際照明委員會座標(CIE)為(0.2,0.2)，此分子不僅為少數TADF發出白光分子，更提供了新一代白光單層元件的一個有潛力分子。 我們報告了一種新的鋅配合物，可以增強基於熱延遲活化螢光（TADF）的綠藍色有機發光二極體（OLED）。利用鋅和TADF配體的結合，我們成功合成了具有TADF特性的Zn(PhOBz)-PXZ。時間分辨光致發光（TrPL）研究揭示了 TADF 的發射機制。 DFT計算表明，HOMO和LUMO在基態下分離良好，激發單重態和三重態之間的能量分裂很小。這與先前僅表現出即時螢光的鋅配合物形成鮮明對比。透過氣相沉積併入綠藍色 TADF OLED 系統，成功地展示了綠藍色 OLED。 Zn(PhOBz)-PXZ元件表現出521 nm電致發光(EL)和10.6%的最大外量子效率(EQEmax)，國際照明委員會(CIE)座標為(0.28,0.47)。鋅配合物具有TADF、成本效益高、自然資源更豐富、環境友善的金屬，使其成為未來貴金屬發射體的潛在替代品。

We reported the new host material to boost the multiple resonance-induced thermally activated delayed fluorescence (MR-TADF) based pure deep-blue organic light emitting diodes (OLEDs) toward further shortening the emission full width at the half maximum (FWHM). Based on an unusual asymmetric design concept, we synthesized two new host compounds Bz2cbz and Bz2cb, which, despite possessing a compact and rigid molecular packing in crystal, show pure amorphous morphology via vapor deposition, as confirmed by the grazing-incidence wide-angle X-ray scattering (GIWAXS) analysis. Via incorporating a promising MR-TADF emitter, ν-DABNA-O-Me, into Bz2cbz and Bz2cb films, the highly pure deep-blue OLEDs were successfully demonstrated. The blue index of the device we fabricated reaches up to 253.For the use of Bz2cbz, the device shows maximum external quantum efficiency (EQEmax) of 28.2% with a turn-on voltage of 3.0 V, electroluminescence emission peak at 464 nm. Importantly, the emission full width at half maximum (FWHM) of 22 nm accompanied by the reduction of the 0-1 vibronic sideband. As a result, the corresponding Commission Internationale de l’Eclairage (CIE) coordinates of (0.13, 0.07) are superior to the best of the reported data (FWHM: 23 nm and CIE (0.13, 0.10) using a symmetric host material DOBNA-tol. We thus propose that the amorphous environment of host Bz2cbz leads to the homogeneous distribution of the guest ν-DABNA-O-Me, resulting in a reduction of the inhomogeneous sites of ν-DABNA-O-Me and hence the spectral narrowing of the emission. The asymmetric configuration of host materials may play a necessary role for the amorphous film formation via vapor deposition, which turns out to be an important factor to externally fine-tune the MR-TADF OLEDs toward even higher colour purity. Here, we report a newly synthesized thermally activated delayed fluorescence (TADF) material that emits white light. This phenomenon arises from both its monomer and aggregate states. Through analysis of its transient spectra and lifetime, we deduced that the generation of white light is due to the presence of two distinct structures. Further TEM analysis indicates that the molecules form a spherical structure through crystallization, with an outer shell and inner stacking. Confocal microscopy clearly shows that the outer layer emits blue light, while the inner layer emits green light. By incorporating this material into a non-doped device, the device exhibits Commission Internationale de l’Eclairage (CIE) coordinates of (0.27, 0.30). This molecule not only represents one of the few TADF emitters producing white light but also holds promise for a new generation of white light single-layer devices. We report a new zinc complex that enhances thermally activated delayed fluorescence (TADF) based greenish-blue organic light-emitting diodes (OLEDs). Utilizing the combination of zinc and TADF ligand, we successfully synthesized Zn(PhOBz)-PXZ with TADF properties. Time-resolved photoluminescence (TrPL) studies revealed the emission mechanism of TADF. DFT calculations showed that the HOMO and LUMO are well-separated in the ground state, and the energy splitting between the excited singlet and triplet states is small. This is in contrast to previous Zn complexes that only exhibited prompt fluorescence. Via vapor deposition incorporating into a greenish-blue TADF OLED system, greenish-blue OLEDs were successfully demonstrated. The Zn(PhOBz)-PXZ device exhibits 521 nm electroluminescence (EL) and a maximum external quantum efficiency (EQEmax) of 10.6%, with Commission Internationale de l’Eclairage (CIE) coordinates of (0.28, 0.47). Zinc complexes have TADF, cost-effectiveness, greater abundance of natural resources, environmentally friendly metals, making them potential replacements for future precious metal emitters.