New generations of spirobifluorene regioisomers for organic electronics: tuning electronic properties with the substitution pattern

Poriel, Cyril; Sicard, Lambert; Rault‐Berthelot, Joëlle

doi:10.1039/c9cc07169e

Cited by 97 publications

(95 citation statements)

References 78 publications

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“…SF4‐TPE has 9,9‘‐spirobifluorene backbone and extended from C4 site with triphenylene unit. The molecule consists of pure hydrocarbon components, and the spiro structure can ensure good stability and reduced molecular bond dissociation even under high current injection, [ 36 ] providing a stable and consistent platform for exciton generation and transfer. [ 37–39 ] The C4 site is chosen because of twisted structure, however, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) cannot be fully separated because the lack of obvious electron donating/withdrawing groups in pure hydrocarbon aromatic compound ( Figure e,f).…”

Section: Resultsmentioning

confidence: 99%

All‐Fluorescence White Organic Light‐Emitting Diodes Exceeding 20% EQEs by Rational Manipulation of Singlet and Triplet Excitons

Tang

et al. 2020

Adv Funct Materials

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White organic light-emitting diodes (WOLEDs) composed of conventional fluorophores possess color purity, low efficiency roll-off, and rare metal absence, but suffer from theoretical limits due to the lack of triplet utilization. Due to the different diffusion distance for singlets and triplets, multiple Förster resonance energy transfer (FRET) channels can be adequately built up. Herein, besides the complementary component, a blue fluorescence layer, hosted by pure hydrocarbon material SF4-TPE, is put forward as the spatial exciton manipulating layer to rationally allocate singlets and triplets to the corresponding channels. Hence, singlets are captured by the blue fluorophore, diffused triplets subsequently undergo energy resonance between the blue fluorophore and green assistant, and up-conversion effect for eventual emission from the yellow fluorophore. Owing to the utilization of singlets and triplets, all-fluorescence WOLEDs exhibit high efficiency exceeding 20%, with slight efficiency roll-off even under high luminance of 5000 cd cm −2 . Moreover, CIE coordinates can be surrounding and precisely inside the American National Standard Institute (ANSI) quadrangles, as well as outstanding color stability (ΔCIE-(x, y) within (0.001, 0.012)) from 300 to 13000 cd cm −2 .The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201910633.white emission and achieved a power efficiency (PE) of 0.5 lm W −1 . However, due to the deficiency of utilizing triplets, the WOLEDs based on all-fluorescence emitters can hardly break the 25% theoretical limitation of internal quantum efficiency (IQE). [4,5] Alternatively, the exploitation of rare metallic phosphorescent complexes and thermally activated delayed fluorescence (TADF) emitters that can harvest all the electrogenerated excitons [6] become the fundamental and mainstream study on constructing high-efficiency WOLEDs in the past decade. [2,[7][8][9][10][11][12][13][14][15] However, allphosphorescence WOLEDs still suffer from the intrinsic deficiencies including rare metal reliance, color impurity, and fragile operational stability for blue phosphors, [16,17] while all-TADF WOLEDs present severe efficiency roll-off because of triplet-triplet annihilation (TTA) at high luminance and unsatisfactory Commission International de l'Eclairage (CIE) coordinates deviation. [18,19] Thus, hybrid combinations, that is, leveraging TADF/ phosphorescence, fluorescence/phosphorescence or fluorescence/TADF emitters, are also proposed for WOLEDs. [20][21][22][23][24][25] Recently, the efficiency of fluorescence OLEDs can be dramatically improved by TADF assistant technique, in which TADF materials play as "triplet exciton pump" (not emitter) to up-converse triplets in conventional fluorescence emitters to approach 100% IQEs. [26] This technique has made promising progress in monochromatic emitting dyes with relatively low-lying states, such as green, yellow, and red fluorophores. [27][28][29] Thus, it seems reasonable and accessibl...

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Section: Resultsmentioning

confidence: 99%

All‐Fluorescence White Organic Light‐Emitting Diodes Exceeding 20% EQEs by Rational Manipulation of Singlet and Triplet Excitons

Tang

et al. 2020

Adv Funct Materials

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“…These hosts mSPh, mSPh 2 , mSTPh and mSTPh 2 are constructed by the assembly of the most basic PHC unit, i.e. a benzene ring, in a spiro conguration 29,50 and can be easily synthesized in a short and highly efficient manner. We show how the electronic and physical properties can be tuned as a function of the substitution pattern and nature of the substituents.…”

Section: Discussionmentioning

confidence: 99%

“…2a, all the hosts displayed similar UV-vis absorption proles, with thin and high intensity bands at 310-311 nm in dilute toluene solutions (10 À5 M) as commonly observed in SBF based compounds. 28,29 In addition to this band, the four compounds display a red-shied band at either 317 nm (low molar absorption coefficient, 3, and low oscillator strength, see natural transition orbitals calculations in the ESI †) for the two monosubstituted SBFs, mSPh and mSTPh, or at 324/325 nm (high 3 and high oscillator strength, ESI †) for the two disubstituted ones, mSPh 2 and mSTPh 2 . This reveals an electronic coupling between the uorene backbone and one or two phenyl/terphenyl substituents, which is indicated in the density of the pendant phenyl units in hole and electron states ( Fig.…”

Section: Synthesis and Characterizationmentioning

confidence: 99%

Evolution of pure hydrocarbon hosts: simpler structure, higher performance and universal application in RGB phosphorescent organic light-emitting diodes

et al. 2020

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“…This not only results in a different geometry but also to a different electronic coupling between the fragments (for a precise study of the influence of a linkage on the electronic properties, please see refs. [27b,44b,88]). The PL spectrum of 72 is then blue shifted compared to that of 71 (439 vs 448 nm, Table 20 ).…”

Section: Donor/acceptor (D/a) Designmentioning

confidence: 99%

Blue Single‐Layer Organic Light‐Emitting Diodes Using Fluorescent Materials: A Molecular Design View Point

Poriel

Rault‐Berthelot

2020

Adv Funct Materials

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technology is mastered, it suffers from a real complexity, a high cost, and is time-consuming. Simplifying the multilayer structure with the so-called single-layer OLEDs (SL-OLEDs), the simplest device only made of the electrodes and the EML has hence rapidly appeared as a promising and appealing solution in this technology (Scheme 2, left).However, removing the functional organic layers of an OLED stack often leads to a dramatic decrease of the performance and reaching high efficiency blue SL-OLEDs has required intense researches and especially in term of materials design. Indeed, if one removes all the organic layers surrounding the EML, the efficient injection, transport, and recombination of charges within the device, should be insured by the EML itself and therefore the fluorophore. However, this appears to be a real obstacle to cross for blue emitting materials. Indeed, blue fluorophores usually possess a high HOMO and a low LUMO energy rendering the injection of charges in such materials very difficult. This has been one of the main issue to address in this field. Common properties required for high-performance blue emitting materials can be summarized as follows: 1) blue light emission between 380 and 500 nm with maximum wavelength around 450 nm; 2) a narrow full width at half maximum less than 60 nm; which produces low Commission Internationale de l'Eclairage (CIE) y-coordinate of less than 0.10 for TVs and cell phones; 3) thermal and morphological stability for stable device operation and a long device lifetime; 4) balance charge transport between electrons and holes flow and 5) adequate HOMO/LUMO energy levels for charge recombination and injection.Gathering all these properties in a single molecule is far from being an easy task and requires very precise designs. Indeed, as soon as one tries to adjust the HOMO/ LUMO energy levels of an organic semiconductor (OSC) with the Fermi levels of OLED electrodes, its gap is contracted and the emission wavelength is bathochromically shifted. This design strategy can hence lead to a material in which the charges can be more easily injected (the gap is contracted) but with an emission wavelength no more in the blue region. Trying to find the best compromise between adequate HOMO/LUMO energy and a blue emission has been the main challenge to address in the molecular design of efficient fluorophores for blue SL-OLEDs. This particularity has strongly restrained the development of such materials. However, for the last 30 years, research groups have developed many different molecular design strategies, which have led in some cases to high performance blue SL-OLEDs. Reaching high performance SL-OLEDs by molecular engineering of the fluorophore and Cyril Poriel is

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New generations of spirobifluorene regioisomers for organic electronics: tuning electronic properties with the substitution pattern

Abstract: In the present feature article, we present the new generations of spirobifluorenes for organic electronics and we detail the impact of positional isomerism on the electronic properties and device performance.

Cited by 97 publications

References 78 publications

All‐Fluorescence White Organic Light‐Emitting Diodes Exceeding 20% EQEs by Rational Manipulation of Singlet and Triplet Excitons

All‐Fluorescence White Organic Light‐Emitting Diodes Exceeding 20% EQEs by Rational Manipulation of Singlet and Triplet Excitons

Evolution of pure hydrocarbon hosts: simpler structure, higher performance and universal application in RGB phosphorescent organic light-emitting diodes

Blue Single‐Layer Organic Light‐Emitting Diodes Using Fluorescent Materials: A Molecular Design View Point

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