Aggregation-induced narrowband isomeric fluorophores for ultraviolet nondoped OLEDs by engineering multiple nonbonding interactions

Traditional donor-acceptor type organic luminescent materials usually suffer from unfavorable spectral broadening and fluorescence quenching problems arising from strong inter/intra-chromophore interactions in aggregation state.Here,two ultraviolet carbazole-pyrimidine isomers(named o-DCz-Pm and m-DCz-Pm)with novel aggregation-induced narrowband phenomenon are constructed and systematic investigated by experiments and theoretical simulations.Benefitting from strengthened steric hindrance and multiple noncovalent interactions,the nonradiative decay,vibrational motion,and structural relaxation of singlet state can be effectively suppressed in aggregation state.Consequently,the electroluminescence peak of 397 nm,full width at half maximum of 21 nm and external quantum efficiency of 3.4%are achieved simultaneously in nondoped o-DCz-Pm-based device.This work paves an avenue toward the development of high-performance narrowband nondoped ultraviolet materials and organic light-emitting diodes.

High-Mobility Ambipolar Benzodifurandione-Based Copolymers with Regular Donor–Acceptor Dyads Synthesized via Aldol Polycondensation

In this study,a family of three benzodifurandione-baseddonor–acceptor(D–A)copolymers,namelypoly[3,7-bis((E)-1-(4-octadecyldocosyl)-2-oxo-6-yl-indolin-3-ylidene)-3,7-dihydrobenzo[1,2-b:4,5-b′]difuran-2,6-dionealt-(E)-1,2-di(2,2′-bithiophen-5-yl)ethene](PBDO-DTE),poly[3,7-bis((E)-7-fluoro-1-(4-octadecyldocosyl)-2-oxo-6-yl-indolin-3-ylidene)-3,7-dihydrobenzo[1,2-b:4,5-b′]difuran-2,6-dione-alt-(E)-1,2-di(2,2′-bithiophen-5-yl)ethene](PFBDO-DTE),and poly[(3E,7E)-3,7-bis(1-(4-octadecyldocosyl)-2-oxo-6-yl-1,2-dihydro-3Hpyrrolo[2,3-b]pyridin-3-ylidene)-3,7-dihydrobenzo[1,2-b:4,5-b′]difuran-2,6-dione-alt-(E)-1,2-di(2,2′-bithiophen-5-yl)ethene](PNBDO-DTE),was designed and synthesized by employing aldol polycondensation reactions between benzodifurandione and bisindolin-2-ones in high yields.Further incorporation of fluorine or sp2-hybridized nitrogen atoms on the bisindolin-2-one unit induced S…F or S…N nonbonding interactions-locked polymeric conjugated backbones for PFBDO-DTE and PNBDO-DTE,respectively.Ultraviolet photoelectron spectroscopy and inverse photoemission spectroscopy measurements revealed that the two copolymers have lower frontier molecular orbitals than that of PBDO-DTE.Atomic force microscopy and two-dimensional grazing-incidence wide-angle X-ray scattering investigations indicated the PNBDO-DTE copolymer could form more ordered molecular aggregation in the solid state than PBDO-DTE and PFBDO-DTE copolymers.We fabricated thin film transistors based on these copolymers on plastic polyethylene terephthalate substrates,and they all showed ambipolar charge transport characteristics.Among them,the PNBDO-DTE-based devices afforded optimal charge transport characteristics with high hole and electron mobilities of 5.16 and 1.33cm^(2)V^(−1)s^(−1),respectively.Our study highlights that aldol polycondensation would be an extremely useful protocol in constructing high-performance polymer semiconductors.