Handbook of Aggregation-Induced Emission, Volume 3. Группа авторов

Handbook of Aggregation-Induced Emission, Volume 3 - Группа авторов


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of the emission wavelength. Based on this emitter, the nondoped OLED devices exhibited red emission peaking at 650 nm (CIE = 0.67, 0.32), with CE and EQE of 3750 cd/m2 and 3.7%, which is higher than the BTPEBTTD‐based OLED device, as a result of weakened intermolecular interaction [75]. Xu et al. prepared two new AIE luminogens V2BV2 and T2BT2 (Figure 1.4), composed of TD cores, TPA bridges, and AIE‐active end‐capper. With multiple TPE units, the luminogens exhibited AEE (aggregation‐enhanced emission) properties. The nondoped OLED devices ITO/NPB (60 nm)/sample (20 nm)/TPBi (40 nm)/LiF (1.0 nm)/Al (100 nm) were fabricated with emission of 590 nm for T2BT2 and 616 nm for V2BV2, and the maximum PE was found at 6.81 cd/A and 4.96 lm/W for the T2BT2 device [76]. Qin et al. utilized the moieties of TPE, TD and arylamines triphenyal amine, or N,N′‐di(1‐naphthyl)‐N,N′‐diphenyl‐(1,1′‐biphenyl)‐4,4′‐diamine (NPB) to two novel red AIE‐active emitters TPE‐TPA‐BTD (TTB) and TPE‐NPA‐BTD (TNB) (Figure 1.4), which can be used as EMLs or both HTLs and EMLs for OLEDs with good EL performance. The nondoped OLED based on these emitters as EML can obtain EQE of up to 3.9%, while the bilayer OLED using TTB as HTLs and EMLs can reach EQ of up to 2.5%, with much simpler OLED structure [77]. Wang and coworkers prepared two new red AIE emitters composed by the stronger electron‐deficient core of [1,2,5]thiadiazolo[3,4‐g]quinoxaline or benzo[1,2‐c; 4,5‐c′]bis[1,2,5]thiadiazole and TPE end‐cappers. The resulting luminogens TDQ and BBT (Figure 1.4) show the AEE effect and their films emit NIR PL and EL emissions peaked in the range of 704–883 nm. Efficient nondoped NIR OLEDs were achieved using these materials as emitting layers, with a maximum EQE of 0.89% [78].

Schematic illustration of molecular structures of red conventional AIE-active emitters.

      1.2.4 Aggregation‐induced Emission‐active Emitters‐Based White OLED

Schematic illustration of molecular structures of conventional AIE-active emitters to construct WOLEDs.

      Although the doping approach can effectively overcome the ACQ problems, it usually requires precise control over the dopants concentration, and the resulting emission also suffers from the drawbacks of insufficient energy transfer. From this point, nondoped methodology can solve such problem, but it usually posed a challenge for the fabrication, because the EMLs with normal emitters for WOLEDs should be ultrathin, about 1 Å, in order to avoid the ACQ disadvantages [80]. In this prospective, the AIE luminogens can overcome these drawbacks of ultrathin fabrication, because they exhibited high PLQYs in aggregated state, therefore showing high potentials especially in nondoped WOLEDs. Tang et al. took advantage of bluish‐green AIE emitter of TTPEPy (Figure 1.5) and red AIE emitter of BTPETTD to prepare nondoped fluorescent WOLEDs, which exhibited the maximum luminance, CE, and PE, of 18 000 cd/m2, 7.4 cd/A, and 4 lm/W, respectively, with a reduced efficiency roll‐off, a high color rendering index of 90, and high color stability over a wide range of driving voltages [81]. To further simplify the process and reduce the cost of OLED, nondoped bilayer WOLED was fabricated by two emitters BTPETTD and DPPi with complementary colors of red and blue, respectively, while BTPETTD (Figure 1.5) and DPPi also served as the HTL and ETL, respectively. Through such a configuration, most of the excitons recombined in the DPPi layer gave off blue emission, while excitons captured by BTPETTD emitted red EL. And the bilayer WOLED based on the combination of these two emissions provided an efficient and stable white‐color emission, with CIE coordinates of (0.31, 0.31), CE of 4.2 cd/A at 1000 cd/m2 [82]. Similarly, Ma et al. used prepared nondoped WOLEDs by adopting two aggregation‐induced enhanced emission (AIEE) materials, TDPVBi and CN‐DPASDB (Figure 1.5) with blue and orange emission, respectively. And the related WOLED exhibited a maximum CE, PE, and luminance of 7.9 cd/A, 6.2 lm/W, and 25 350 cd/m2, respectively [83].


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