Construction of efficient solid emitters with conventional and AIE luminogens for blue organic light-emitting diodes
作者:Zujin Zhao、Shuming Chen、Chunmei Deng、Jacky W. Y. Lam、Carrie Y. K. Chan、Ping Lu、Zhiming Wang、Bingbing Hu、Xiaopeng Chen、Ping Lu、Hoi Sing Kwok、Yuguang Ma、Huayu Qiu、Ben Zhong Tang
DOI:10.1039/c1jm10221d
日期:——
9,9-Bis(9-heptyl-3-carbazolyl)fluorenes (BPyBCF, BAnBCF, BTPABCF, and BTPEBCF, where B = Bis, Py = pyrene, C = carbazole, F = fluorene, An = anthracene, TPA = triphenylamine, and TPE = tetraphenylethene) with different chromophoric units at the 2,7-positions are synthesized in moderate to high yields (52–89%) by Suzuki coupling reactions of 9,9-bis(9-heptyl-3-carbazolyl)-2,7-dibromofluorene with the corresponding arylboronic acid and utilized as active layers for the construction of blue organic light-emitting diodes (OLEDs). BPyBCF, BAnBCF and BTPABCF emit intense blue light with high fluorescence quantum yields (ΦF = 75–94%) in solution. However, they exhibit much lower ΦF values (30–61%) in the film state, revealing that aggregate formation has quenched their light emission. On the contrary, BTPEBCF is weakly emissive in solution (ΦF = 0.3%) but becomes a strong emitter (ΦF = 100%) when fabricated into solid film, demonstrating a phenomenon of aggregation-induced emission (AIE). Restriction of intramolecular rotation and suppression of intermolecular interactions due to the propeller-like tetraphenylethene unit are responsible for the AIE phenomenon. All the luminogens are thermally and morphologically stable, showing high glass-transition (Tg = 109–147 °C) and thermal-degradation temperatures (Td = 396–478 °C). Non-doped OLEDs using BPyBCF, BAnBCF, and BTPABCF as light-emitting layers are constructed, which give blue electroluminescence with maximum current (ηC,max) and external quantum (ηext,max) efficiencies of 4.8 cd A−1 and 2.3%. With the same device configuration, BTPEBCF shows higher ηC,max and ηext,max values of 7.9 cd A−1 and 2.9%, respectively, thanks to its AIE feature.
9,9-双(9-庚基-3-咔唑基)芴(BPyBCF、BAnBCF、BTPABCF 和 BTPEBCF,其中 B = 双,Py = 芘,C = 咔唑,F = 芴,An = 蒽,TPA = 三苯胺,TPE = 四苯乙烯)的 2、通过 9,9-双(9-庚基-3-咔唑基)-2,7-二溴芴与相应芳基硼酸的铃木偶联反应,以中等至高产率(52-89%)合成了这些化合物,并将其用作构建蓝色有机发光二极管(OLED)的活性层。BPyBCF、BAnBCF 和 BTPABCF 在溶液中能发出强烈的蓝光,具有很高的荧光量子产率(ΦF = 75-94%)。然而,它们在薄膜状态下的 ΦF 值(30-61%)要低得多,这表明聚集体的形成淬灭了它们的光发射。相反,BTPEBCF 在溶液中的发射率很低(ΦF = 0.3%),但在制成固体薄膜后却变成了强发射体(ΦF = 100%),这表明存在聚集诱导发射(AIE)现象。螺旋桨状四苯基乙烯单元限制了分子内旋转,并抑制了分子间的相互作用,这是造成 AIE 现象的原因。所有发光体都具有热稳定性和形态稳定性,显示出较高的玻璃转化温度(Tg = 109-147 ℃)和热降解温度(Td = 396-478 ℃)。利用 BPyBCF、BAnBCF 和 BTPABCF 作为发光层,构建了无掺杂有机发光二极管,可发出蓝色电致发光,最大电流(ηC,max)和外部量子(ηext,max)效率分别为 4.8 cd A-1 和 2.3%。在相同的器件配置下,BTPEBCF 由于其 AIE 特性,ηC,max 和 ηext,max 值分别高达 7.9 cd A-1 和 2.9%。