Non‐Doped Sky‐Blue OLEDs Based on Simple Structured AIE Emitters with High Efficiencies at Low Driven Voltages

Abstract

Blue organic light-emitting diodes (OLEDs) are necessary for flat-panel display technologies and lighting applications. To make more energy-saving, low-cost and long-lasting OLEDs, efficient materials as well as simple structured devices are in high demand. However, a very limited number of blue OLEDs achieving high stability and color purity have been reported. Herein, three new sky-blue emitters, 1,4,5-triphenyl-2-(4-(1,2,2-triphenylvinyl)phenyl)-1H-imidazole (TPEI), 1-(4-methoxyphenyl)-4,5-diphenyl-2-(4-(1,2,2-triphenylvinyl)phenyl)-1H-imidazole (TPEMeOPhI) and 1-phenyl-2,4,5-tris(4-(1,2,2-triphenylvinyl)phenyl)-1H-imidazole (3TPEI), with a combination of imidazole and tetraphenylethene groups, have been developed. High photoluminescence quantum yields are obtained for these materials. All derivatives have demonstrated aggregation-induced emission (AIE) behavior, excellent thermal stability with high decomposition and glass transition temperatures. Non-doped sky-blue OLEDs with simple structure have been fabricated employing these materials as emitters and realized high efficiencies of 2.41 % (4.92 cd A , 2.70 lm W ), 2.16 (4.33 cd A , 2.59 lm W ) and 3.13 % (6.97 cd A , 4.74 lm W ) for TPEI, TPEMeOPhI and 3TPEI, with small efficiency roll-off. These are among excellent results for molecules constructed from the combination of imidazole and TPE reported so far. The high performance of a 3TPEI-based device shows the promising potential of the combination of imidazole and AIEgen for synthesizing efficient electroluminescent materials for OLED devices.

Aggregation‐Induced Dual‐Phosphorescence from Organic Molecules for Nondoped Light‐Emitting Diodes

“…Recently, luminescent materials, especially aggregation‐induced emission luminogens (AIEgens), have been a hotspot due to their wide applications in biosensors, information storage, and organic light‐emitting diodes (OLEDs) . The main benefit of aggregation‐induced emission (AIE) is the manifestation and augmentation of radiative excited states for organic molecular systems .…”

Violet-Blue Emitters Featuring Aggregation-Enhanced Emission Characteristics for Nondoped OLEDs with CIEy Smaller than 0.046

“…Although the doping devices can solve these problems, the device configurations are complicated, making the practical cost increased. To avoid these adverse factors, a strategy of a molecularly melding aggregation-induced emission (AIE) core with donor (D) and acceptor (A) groups was proposed, which has been used for the fabrication of nondoped OLEDs. − Furthermore, these AIE luminogens (AIEgens) can also improve the charge injection and carrier transport in OLEDs, leading to an enhancement in the electroluminescence efficiency of the devices when using them as emitting layers (EMLs). − However, reports on efficient and stable AIEgen-based violet-blue OLEDs with CIEy smaller than 0.046 are rare.…”

Imidazole derivatives for efficient organic light-emitting diodes

“…The three new sky-blue emitters TPEI, TPEMeOPhI, and 3TPEI, with a combination of imidazole and TPE groups, were developed [105]. A high PLQY was obtained for these materials.…”