Star-Shaped Single-Polymer Systems with Simultaneous RGB Emission: Design, Synthesis, Saturated White Electroluminescence, and Amplified Spontaneous Emission

Lai

et al. 2018

The Chemical Record

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In recent years, conjugated starburst molecules, which possess a core unit with radial arms linked to the central axle, have become the research topic owing to their well-defined chemical structures, good solution processability, excellent reproducibility, and superior optoelectronic properties. The increasing interest in starburst systems is evidenced by progressively more frequent investigation on the use of these materials in optoelectronics. The ability to modify chemical structures through control over the core and arms on a molecular level can directly affect the electronic and electroluminescent characteristics of the resulting materials. In this review, we summarize and discuss main progress in our group concerning the rapidly developing field, in which strategies for the design and construction of starbursts are presented at length. Moreover, their application in organic light-emitting diodes (OLEDs) and organic semiconductor lasers (OSLs) are demonstrated as well, exploring the influence of molecular structures on the optoelectronic properties. Challenges and outlooks are also given at last.

Section: Starburst Systems For Oslsmentioning

confidence: 99%

Section: Starburst Systems For Oledsmentioning

confidence: 99%

Design and Synthesis of Conjugated Starburst Molecules for Optoelectronic Applications

Lai

et al. 2018

The Chemical Record

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“…Organic p-conjugated semiconductors have been intensely investigatedf or optoelectronics, such as organic light-emitting diodes (OLEDs), [1,2] organic field-effect transistors, [3,4] organic solar cells, [5] and organics emiconductor lasers (OSLs). [6,7] Despite recent advances in optically pumped organic lasing, [8][9][10][11] achieving electrically pumped organic lasing still remains ac ritical challenge. [12] The realization of electrically pumped lasing requires gain media with high charge mobility,h igh gain properties, and excellent thermal and optical stability,e tc.…”

Section: Introductionmentioning

confidence: 99%

Donor–Acceptor Type Pendant Conjugated Molecules Based on a Triazine Center with Depressed Intramolecular Charge Transfer Characteristics as Gain Media for Organic Semiconductor Lasers

Sang

et al. 2020

Chemistry A European J

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A set of fluorene‐capped pendant conjugated molecules (T‐m and T‐p), which consist of a triazine center with three carbazole substituents as the donor–acceptor (D‐A) type pendant structure, were designed, synthesized, and investigated as gain media for organic semiconductor lasers (OSLs). In particular, varying the capping positions of the fluorene units on the pendant core structures results in significantly different intramolecular charge transfer (ICT) properties, where T‐m manifested depressed ICT characteristic and high fluorescence quantum yield. The lowest amplified spontaneous emission (ASE) threshold in neat films was recorded as 1.9 μJ cm−2 for T‐m and 83.8 μJ cm−2 for T‐p, which indicated that the depressed ICT characteristics in the case of T‐m help to enhance the ASE properties. Remarkably, the ASE threshold remained almost unchanged and the ASE spectra showed very small shifts (within 1 nm) for T‐m with film samples annealed up to 180 °C in open air. In contrast, its linear counterpart 2FEtCz‐m showed a clearly increased ASE threshold upon annealing above 100 °C. The results suggest that the selective construction of conjugated pendant molecules with depressed ICT characteristics is beneficial for finely modulating the optical and electrical properties as well as improving the thermostability and photostability, which manifests the great potential as a robust gain media for OSLs.

“…According to previousc ontributions, av ariety of conjugated starburst materials with various cores such as truxene, pyrene and triazatruxene, demonstrating efficient electroluminescence and prominent lasing behaviors have been designed and synthesized. [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] Because of the synergetic effects of differentm oieties, the molecules manifest good solubility andg reat film-forming behaviors as wella se xcellent stability and high electroluminescence, implying that such starburst molecular structures are promising to achieve excellent lasing behaviors with low thresholds. It is worthwhile to mention that the ability to adjust the architectures by modulation over the core and arms in the terms of am olecular level shows ad irect impact on the electronic and electroluminescent characteristics of the molecules.…”

Section: Introductionmentioning

confidence: 99%

Low‐Threshold Non‐Doped Deep Blue Lasing from Monodisperse Truxene‐Cored Conjugated Starbursts with High Photostability

Chemistry An Asian Journal

Lai

et al. 2019

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Herein, the photophysical, morphological, optical gain characteristics of a set of trigonal monodisperse starburst conjugated macromolecules (Tr1‐Tr4) have been systematically investigated in order to elucidate the influence of the molecular structures on their optoelectronic performance. With increasing the oligofluorene arm length, absorption spectra were red‐shifted progressively, whereas an increase in photoluminescence quantum yields (PLQYs) and optical gain coefficients, and a corresponding reduction in amplified spontaneous emission (ASE) thresholds and loss coefficients were observed for Tr1‐Tr3 except for Tr4. The results indicate that the effective conjugation length become saturated for Tr3 in this system. Impressively, the resulting molecules manifested very low ASE thresholds (4.4–11.6 μJ cm−2) with high photostability, as well as high thermal stability. One dimensional distributed feedback (DFB) lasers exhibited a minimum lasing threshold of 10.38 nJ pulse−1 (0.86 kW cm−2, 4.325 μJ cm−2) for Tr3. It should be emphasized that the ASE threshold of Tr1‐Tr4 was nearly unchanged from room temperature to 200 °C. The results suggest that this kind of truxene‐cored conjugated starbursts with high photostability and low lasing thresholds are rather promising gain media for organic semiconductor lasers.