Manipulating the Molecular Backbone to Achieve Highly Emissive Sky‐Blue AIEgens and Their Applications in Nondoped Organic Light‐Emitting Diodes

Abstract

performance are also necessary. [6] Unfortunately, unlike the red and green emitters, highly emissive blue OLMs in devices are rare due to their wide bandgap, but recently it has been demonstrated that OLMs with impressive and robust solid-state photoluminescence (PL) efficiency is beneficial to enhance their EL performance in OLEDs significantly. [7] Therefore, developing highly emissive blue OLMs in aggregated solid state becomes one of the key procedures to achieve the corresponding efficient OLEDs.For most conventional OLMs, impressive emissive features can be obtained in their dilute solutions, while weak or completely quenched emission was observed in the solid state for To enhance the luminescent performance of aggregation-induced emission luminogens (AIEgens) in organic lightemitting diodes (OLEDs) but also retain their blue emission color, 2-CzTPE and 2,7-CzTPE with promising AIE features are synthesized to balance the trade-off between twisted molecular conformation and enlarged molecular conjugation. As observed, although 2-CzTPE, which contains twisted molecular backbone, could suppress the emission-quenching π-π stacking, an inferior luminescent performance with photoluminescence quantum yields (PLQYs) of 23.12% occurs in aggregated solid state for its limited molecular conjugation, then leading to an inferior electroluminescence (EL) performance with external quantum efficiency (EQE) of 1.9%. However, after molecular engineering of backbone to enlarge its conjugation in 2,7-CzTPE, significantly enhanced PLQY value of 60.63% is achieved in solid state. Interestingly, the emission of 2,7-CzTPE remains in the blue region, which is even identical to that of 2-CzTPE in aggregates. Finally, much better EL performance in nondoped OLEDs with current efficiency of 7.38 cd A −1 , power efficiency of 6.81 lm W −1 , and also EQE of 3.0% is achieved for 2,7-CzTPE-based devices. These findings demonstrate that manipulating molecular backbone to achieve the balanced molecular conjugation and twisted conformation is an efficient way to obtain highly emissive blue AIEgens in both aggregated state and OLEDs devices.

A Facilely Synthesized Dual‐State Emission Platform for Picric Acid Detection and Latent Fingerprint Visualization

“…Lifetimes of 26.2, 14.6, and 21.8 ns were measured for PTCA‐C4, PTCA‐C6, and PTCA‐C12 in the solid state, respectively, thereby leading to altered k r values and k nr values. A much higher k r value was determined in the case of PTCA‐C6, thus leading to open radiative decay channels and high‐intensity emission . It can be easily understood that in the case of PTCA‐C4, emission‐quenching intermolecular stacking may still exist with the short alkyl chains, thus leading to moderate fluorescence performance.…”

“…Am uch higher k r value was determined in the case of PTCA-C6, thus leadingt oo pen radiatived ecay channels and high-intensity emission. [40] It can be easily understood that in the case of PTCA-C4, emission-quenching intermolecular stacking may still exist with the short alkyl chains, thus leadingtom oderate fluorescence performance. However,i nt he case of PTCA-C12, althoughi ntermoleculars tacking may be prevented, the long chains can be considereda sm olecular rotors, therebyp romoting intramolecular motion in the excited state andl eadingt o the corresponding nonradiative relaxation process, resulting in reduced emission in the solid state.…”

2,7(3,6)-Diaryl(arylamino)-substituted Carbazoles as Components of OLEDs: A Review of the Last Decade

“…It was mentioned that the combination of fragments of carbazole with various conjugated aromatic fragments is favorable for the formation of homogeneous thin films with high T g temperature values. The T g of E1, E3-E6, E9-E10, E14, E17, and E18 were 105,138,65,138,77,70,211,88,170, and 172 • C, respectively. The values of I p for the derivatives E1-E2 and E19-E20 were 5.70 eV, 5.56 eV, 5.17 eV, and 5.30 eV, respectively.…”

“…Structures of the 2,7-diaryl-or 3,6-diaryl-substituted carbazoles, which were used as emitters (E) in the fluorescent OLED devices, are shown in Scheme 7. All the target diarylsubstituted compounds E1-E13 [85][86][87][88][89][90][91][92][93] and E15-E20 [94][95][96][97], except for E14, were obtained during the Suzuki reaction of the di-halogenated carbazoles with the corresponding boronic acids or their esters. The objective material E14 was synthesized by fusing triphenylethylene and one dimesitylboron group moiety into a system, with one attached to the carbazole fragment [98].…”

Butterfly‐Shaped Thiophene‐Pyridine Hybrids: Green Electroluminescence and Large Third‐Order Optical Nonlinearities

“…[8][9][10] Moreover, due to the advantages like excellent thermal stability, high purity, good thin film formation and solution processability of star/butterfly-shaped molecules over the linear molecules, they have gained enormous attention in the recent past. [11][12][13][14] To date, there has been a rapid technological development in NLO which demands the rational design and synthesis of organic materials to achieve enhanced nonlinear optical properties. [15] Among the organic materials studied, the high molecular weight π-conjugated molecules with donor-acceptordonor (D-A-D) arrangement have been the attracting candidates due to their extensive π-delocalization which enables intramolecular charge transfer (ICT) between D and A units, providing high polarizability to the system, which results in superior nonlinear optical properties in addition to their fastoptical responses, ease of fabrication, light weight and flexibility.…”