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Steric Rooted Multi-Resonant Thermally Activated Delayed Fluorescent Emitters for Pure Blue Organic Light Emitting Diodes with Ultralow Efficiency Roll-Off
Advanced Functional Materials ( IF 18.5 ) Pub Date : 2023-05-14 , DOI: 10.1002/adfm.202213461
Ezhakudiyan Ravindran 1 , Ho Eon Baek 2 , Hee Won Son 1 , Ji Hyun Park 2 , Yun‐Hi Kim 2 , Min Chul Suh 1
Affiliation  

Multi-resonant thermally activated delayed fluorescent (MR-TADF) materials are blooming for high-resolution organic light-emitting diodes (OLEDs). However, boron/nitrogen (B/N)-integrated MR-TADF emitters suffer severe efficiency roll-off from their strong inter-molecular ππ interactions. Herein, versatile narrowband pure blue emitters (mono-mx-CzDABNA and tri-mx-CzDABNA) are demonstrated featuring a ring-fused extended π-skeleton: a classic steric hindrance and rigidity accessed by integrating with meta-xylene (mx) rotors. tri-mx-CzDABNA shows a narrowband (FWHM, 26 nm) pure blue emission (λmax, 462 nm) with substantial hypsochromic shift (12 nm) while maintaining MR-TADF characteristics. The key solid-state analyses conclude that they conceivably suppress the non-radiative energy loss, thus improving the photoluminescence quantum yield (PLQY > 90%) and rate of reverse intersystem crossing (RISC) (kRISC ≈2.85 × 105 s−1). The integration of tri meta-xylene significantly leads to an enhanced horizontal dipole ratio (HDR) from 65% to 85%. Hyperfluorescent-OLEDs are fabricated using designed MR-TADF as terminal emitter, achieving a narrowband (FWHM, 34 nm) pure blue electroluminescence (λmax, 472 nm) and maximum external quantum efficiency (EQEmax) of 26.97% with magnificently suppressed efficiency roll-off (7.8%) at 1000 cd m−2. So, it is believed that regulation of internal efficiencies and high color purity can amplify the route to achieving a narrowband pure blue emission through new synthetic MR-TADF approaches.

中文翻译:

用于具有超低效率滚降的纯蓝色有机发光二极管的立体根多谐振热激活延迟荧光发射器

多共振热激活延迟荧光(MR-TADF)材料在高分辨率有机发光二极管(OLED)中的应用正在蓬勃发展。然而,硼/氮 (B/N) 集成 MR-TADF 发射器由于其强烈的分子间π - π相互作用而遭受严重的效率滚降。在此,展示了多功能窄带纯蓝色发射器(mono- mx -CzDABNAtri- mx -CzDABNA),具有环稠合扩展π骨架:通过与二甲苯 ( mx ) 转子集成获得的经典空间位阻和刚性。Tri- mx -CzDABNA显示窄带(FWHM,26 nm)纯蓝色发射(λ max,462 nm),具有显着的低色移(12 nm),同时保持 MR-TADF 特性。关键的固态分析得出的结论是,它们可以抑制非辐射能量损失,从而提高光致发光量子产率(PLQY > 90%)和反向系间窜越率(RISC)( k RISC ≈2.85 × 10 5  s -1)。三间二甲苯的整合显着导致水平偶极比 (HDR) 从 65% 提高到 85%。超荧光 OLED 使用设计的 MR-TADF 作为终端发射器制造,实现窄带(FWHM,34 nm)纯蓝色电致发光(λ max,472 nm)和26.97%的最大外量子效率(EQE max ),并且在1000 cd m -2时极大地抑制了效率滚降(7.8%)。因此,人们相信,内部效率和高色纯度的调节可以扩大通过新的合成 MR-TADF 方法实现窄带纯蓝色发射的途径。
更新日期:2023-05-14
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