Deep‐blue light‐emitting polyfluorenes containing spiro[fluorene‐9,9′‐thioxanthene‐S,S‐dioxide] isomers

Abstract

Blue light‐emitting polyfluorenes, PPF‐FSOs and PPF‐SOFs were synthesized via introducing spiro[fluorene‐9,9′‐thioxanthene‐S,S‐dioxide] isomers (2,7‐diyl and 2′,7′‐diyl) (FSO/SOF) into the poly[9,9‐bis(4‐(2‐ethylhexyloxy) phenyl)fluorene‐2,7‐diyl] (PPF) backbone, respectively. With the increasing contents of FSO and SOF moieties, the absorption and PL spectra of PPF‐FSOs show slight red shift, while that of PPF‐SOFs exhibit blue shift, respectively. The HOMO and LUMO levels reduce gradually with increasing SOF unit in PPF‐SOFs. The polymers emit blue light peaked around 430–445 nm and show an excellent spectral stability with the variation in current densities. The distinctly narrowing EL spectra were observed with the incorporation of isomers in the polymers. The full width at half maximum reduced by 15 nm for PPF‐SOFs, resulting in a blue shift with the CIE coordinates from (0.16, 0.11) to (0.16, 0.08). With a device configuration of ITO/PEDOT:PSS/EML/CsF/Al, a maximum luminance efficiency (LEmax) of 2.00 cd A−1, a maximum external quantum efficiency (EQEmax) of 3.76% with the CIE coordinates of (0.16, 0.08) for PPF‐SOF15 and a LEmax of 1.68 cd A−1, a EQEmax of 2.38% with CIE (0.16, 0.12) for PPF‐FSO10 were obtained, respectively. The result reveals that spiro[fluorene‐9,9′‐thioxanthene‐S,S‐dioxide] isomers are promising blocks for deep‐blue light‐emitting polymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2332–2341

Exploring copper as a catalyst for cost effective synthesis of polyfluorenes: an alternative to platinum and palladium

“…The LUMO levels of the polymers were obtained from the HOMO levels and corresponding optical bandgaps. Thus, the calculated LUMO levels for the polymers were − 2.56, [55]. Table 2 compares the electrochemical properties of all copolymers.…”

Perceiving the influence of phenyl-carbazole isomers on sulfone/thioxanthone-based D–A–D hosts: realizing efficient red-phosphorescent OLEDs

“…47 In addition, Li et al 48 reported SpDBTS-based fluorescent emitters and host materials in which donor units such as carbazole, phenyl-carbazole, and diphenylamine were substituted at the 2 0 ,7 0 -position of the sulfonyl rings and the perpendicular arrangement of the spirofluorene ring avoids the strong intermolecular interaction. 49 Peng et al 50 reported a blue-fluorescent emitting polymer with SpDBTS as an acceptor unit in which the donor units were introduced at the 2,7-position of the fluorene ring and the 2 0 ,7 0 -position of the sulfonyl rings. This introduction of a donor at the 2 0 ,7 0 -position of the sulfonyl rings shows poor conjugation along the donor-acceptor-donor backbone by the sp 3 -carbon and sulfonyl groups, which shows blue-shifted emission with intramolecular charge transfer characteristics between the donor and acceptor sulfonyl rings and the fluorene ring not involved in the emission acts as an appendage.…”

Efficient deep‐blue light‐emitting polyfluorenes based on 9,9‐dimethyl‐9H‐thioxanthene 10,10‐dioxide isomers

“…To enable access to deep‐blue PLEDs and improve the comprehensive performance of PFs, electron‐withdrawing units (e.g., 1,3,4‐oxadiazole, 1,2,4‐triazole, 2,4,6‐triphenyl pyridine, dibenzothiophene‐ S , S ‐dioxide (SO)) have been introduced into polymer backbones or side chains to enhance electron injection and balance charge transport 15–19 . Weak conjugate‐structured 20–21 or twisted polymer backbones 22–24 have also been designed to interrupt the conjugation of the polymer backbone and thereby achieve deep‐blue emission. However, incorporation of electron‐withdrawing groups into the polymer backbone leads to charge‐transfer (CT) from electron‐rich units to electron‐withdrawing groups, which results in bathochromic spectra and influences the color purity of blue emission 25,26 .…”