Altering the Conjugation Pathway for Improved Performance of Benzobisoxazole-Based Polymer Guest Emitters in Polymer Light-Emitting Diodes

Intemann, Jeremy J.; Hellerich, Emily; Tlach, Brian C.; Ewan, Monique D.; Barnes, C. A.; Bhuwalka, Achala; Cai, Min; Shinar, J.; Shinar, Ruth; Jeffries‐EL, Malika

doi:10.1021/ma300821m

Cited by 40 publications

(25 citation statements)

References 53 publications

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“…Fluorescence resonance energy transfer (FRET) occurred between donor and acceptor to achieve high quantum yield. At the same time, the design of ethynylene‐linked structures in the main chain of the copolymers was aimed at reducing the energy level difference and obtaining good electron mobility, which resulted from the increasing of effective conjugation length via enforcing the coplanarity of rings . On the other hand, the uracil was modified to the end of the alkyl chain of 9‐position of 3,6‐dibromo carbazole, and then the cross‐linked structure was formed due to the self‐complementary bonding of uracil between adjacent chains.…”

Section: Introductionmentioning

confidence: 93%

Architecture of Conjugated Donor–Acceptor (D–A)‐Type Polymer Films with Cross‐Linked Structures

Huang

Peng

Wang

et al. 2016

Adv Funct Materials

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A series of new donor–acceptor (D–A)‐type semiconducting conjugated polymers (SCPs), which can form cross‐linked structural and supramolecular assembly films by hydrogen‐bonding, is successfully synthesized. The microstructures of supramolecular assembly films are further investigated by X‐ray diffraction (XRD), high‐ resolution transmission electron microscopy (HRTEM), and variable‐temperature Fourier transform infrared (FT‐IR) absorption spectra. As electronic transmission (ET) materials, the SCPs demonstrate superior properties by means of fabricating electron‐only devices with the configuration of ITO/ET (SCPs)/Ca/Al. According to space‐charge‐limited current (SCLC) measurements, fluorine‐containing SCPs exhibit much smaller threshold voltages and much higher electron mobilities than Alq3. Meanwhile, a significant enhancement for their luminescence properties is verified by the photoluminescence (PL) and electroluminescent (EL) spectra of cross‐linked‐type SCPs, compared to non‐cross‐linked‐type SCPs. The fabricated polymer light‐emitting diodes (PLEDs) with the configuration of ITO/PEDOT:PSS/EML (SCPs)/BCP/LiF/Al are able to emit the color from green to red with moderately low turn‐on voltages. These results suggested that cross‐linked D–A‐type SCP can become a potential candidate as a kind of multifunctional materials applied in the field of optoelectronic devices.

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Section: Introductionmentioning

confidence: 93%

Architecture of Conjugated Donor–Acceptor (D–A)‐Type Polymer Films with Cross‐Linked Structures

Huang

Peng

Wang

et al. 2016

Adv Funct Materials

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“…The quantum yield of 4.4 % (excluding minor emission from the PF8‐BT host) is again excellent for solid state emission in this region of the spectrum. The reduction in quantum yield for 5‐BPh 2 relative to 3‐BPh 2 and 4‐BPh 2 is attributed to the energy gap law and to the emission of the PF8‐BT host being less well matched with the significantly red‐shifted absorption band of 5‐BPh 2 resulting in less efficient Förster energy transfer to this guest compound from the host …”

Section: Resultsmentioning

confidence: 99%

“…The reduction in quantum yield for 5-BPh 2 relative to 3-BPh 2 and 4-BPh 2 is attributed to the energy gap law [3] andt o the emission of the PF8-BT hostb eing less well matched with the significantly red-shifted absorptionb and of 5-BPh 2 resulting in less efficient Fçrster energy transfer to this guest compound from the host. [18] The observation of significant emission centred at 789 nm from 5-BPh 2 and also the intense emission for 7-BPh 2 centred at 702 nm is notable as emission from organicc hromophores with l max > 700 nm generally occurs with significantly lower quantum yields even when doped into host materials. [2] The rigid nature of 5-BPh 2 and 7-BPh 2 coupled with the four and five, respectively,q uaternary centres are presumably important for reducing non-radiatived ecay pathwaysi nt he solid state.…”

Section: Electrochemical and Photophysical Propertiesmentioning

confidence: 94%

Highly Emissive Far Red/Near‐IR Fluorophores Based on Borylated Fluorene–Benzothiadiazole Donor–Acceptor Materials

Crossley

Vitórica-Yrezábal

Humphries³

et al. 2016

Chemistry A European J

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Stille, Suzuki-Miyaura and Negishi cross-coupling reactions of bromine-functionalised borylated precursors enable the facile, high yielding, synthesis of borylated donor-acceptorm aterialst hat contain electron-rich aromatic units and/or extendede ffective conjugation lengths. These materials have large Stokes shifts, low LUMO energies, small band-gapsa nd significant fluorescencee mission > 700 nm in solution and when dispersed in ahost polymer. IntroductionNear-infrared (NIR) absorbing ande missive molecules have attracted significanti nterest due to potential applications including night-vison displays, sensors and in-vivo imaging. [1,2] Generating organic NIR emitters that have appreciable quantum yields is challenging due to the energy gap law where the emission efficiency reduces with decreasing energy gap. [3] This is exacerbated in the solid state as aggregation often leads to additionaln on-radiative pathways and significant emission quenching. [4] Onee ffective strategy for accessing low-bandgap materials is to construct p-conjugated systems containing donor (D) and acceptor( A) groups. [5] However, D-A materials with appreciable solid state NIR emissiona re currently rare, [2d] therefore new low-band-gap D-A materials are desirable, particularly if accessible by simple modular routes.Another attractive property of D-A materials is the large degree of controlo ver the electronic and optical properties by rational structural modification.F or example, the coordination of aL ewis acid to aL ewis basic site on an acceptorm oiety has been previously used to generate D-A materials with low LUMO energies and small band-gaps. [6] Ar elated approach that generates D-A materials that are more stable to moisture and Lewis bases appendsB R 2 moietiest oac onjugated framework throughf ormationo faC ÀBb ond and ad ative bond from the acceptor to the boronc entre. [7] We have recently utilised this methodology to synthesise borylated 9,9-dioctylfluorene-benzothiadiazole (F8-BT)c ontaining D-A materials by directedelectrophilicb orylation which concomitantly formsaCBa nd aN !Bb ond. [8] This borylation reactionp lanarises the conjugated backboneg eneratingr igid structures with extended effective conjugation lengths.T hese fused materials showed large Stokes shifts, low band-gaps, were stable to H 2 O and O 2 and wereh ighly emissive in solution and the solid state;f or example, F8-BT-F8 functionalised with aB Ph 2 group was highly emissive in the solid state (PLQY3 3% with l max = 696 nm). [8] Whilst notable it is desirable to develop synthetic routest or apidly access analogues with lower band-gapst hat were highly emissive in the solids tate with emissionf urther into the NIR (l max @ 700 nm).As imple approacht od eliver these materials is to introduce more electron-rich donor units than F8 and/or to extend the effective conjugation length.H owever,c oupling other donor units to F8-BT generates unsymmetric F8-BT-D materials that complicates the electrophilic borylation step, particularly wheree lectr...

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“…11 The dramatic improvement in efficiency of the devices with polymer guests in the CBP host is shown in Fig. The EML was a guest:host system of polymer guest and either PVK or CBP host, or a neat lm of MEH-PPV.…”

Section: Device Efficiencymentioning

confidence: 99%

“…The polymer guests were novel benzobisoxazole (BBO)-containing copolymers, recently described by Intemann et al, 11 and the wellknown poly(2-methoxy-5-(2 0 -ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV), usually used as a neat lm. The polymer guests were novel benzobisoxazole (BBO)-containing copolymers, recently described by Intemann et al, 11 and the wellknown poly(2-methoxy-5-(2 0 -ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV), usually used as a neat lm.…”

Section: Introductionmentioning

confidence: 99%

Fluorescent polymer guest:small molecule host solution-processed OLEDs

et al. 2013

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Solution-processed OLEDs with polymer hosts and polymer or small-molecule guests have been studied extensively. More recently, efficient solution-processed OLEDs with small molecule hosts and small molecule guests were also reported. However, small molecule hosts of polymer guests in solutionprocessed fluorescent OLEDs have not been investigated. In this work guest:host systems consisting of the small molecule 4,4 0 -bis(9-carbazolyl)-biphenyl (CBP) as host to polymer guests such as novel benzobisoxazole (BBO)-containing copolymers and well-known poly(2-methoxy-5-(2 0 -ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) are compared to those with poly(N-vinyl carbazole) (PVK) host, which previously yielded highly efficient phosphorescent OLEDs. In the case of MEH-PPV, guest:host OLEDs are also compared to those with a neat MEH-PPV emitting layer. It is found that replacing the polymer host PVK with the small molecule host CBP improves efficiencies by up to 100%. A blue emissive BBO-polymer:CBP device reaches a luminous efficiency (h L,max ) of 3.4 cd A À1 (external quantum efficiency h ext ¼ 2.4%), while the PVK-based device exhibits h L,max ¼ 1.7 cd A À1 (h ext ¼ 1.2%). A green emissive BBO:CBP OLED exhibits h L,max ¼ 5.7 cd A À1 (h ext ¼ 2.1%), while that in the PVK host is 3.1 cd A À1 (h ext ¼ 1.1%). For MEH-PPV:CBP these values are 3.7 cd A À1 (h ext ¼ 1.4%), compared to 2.9 cd A À1 (h ext ¼ 1.0%) for MEH-PPV:PVK and 0.7 cd A À1 (h ext ¼ 0.4%) for the neat MEH-PPV device. Possible origins of the improvement are discussed, including increased charge mobility, smoother film morphology, and the potential effect of multiple non-coiling host small molecules (in contrast to the likely coiled PVK) surrounding a polymer guest.

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Altering the Conjugation Pathway for Improved Performance of Benzobisoxazole-Based Polymer Guest Emitters in Polymer Light-Emitting Diodes

Cited by 40 publications

References 53 publications

Architecture of Conjugated Donor–Acceptor (D–A)‐Type Polymer Films with Cross‐Linked Structures

Architecture of Conjugated Donor–Acceptor (D–A)‐Type Polymer Films with Cross‐Linked Structures

Highly Emissive Far Red/Near‐IR Fluorophores Based on Borylated Fluorene–Benzothiadiazole Donor–Acceptor Materials

Fluorescent polymer guest:small molecule host solution-processed OLEDs

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