S-Vinyl Sulfide-Derived Pendant-Type Sulfone/Phenoxazine-Based Polymers Exhibiting Thermally Activated Delayed Fluorescence: Synthesis and Photophysical Property Characterization

Abstract

Pendant sulfone/phenoxazine-based homo- and copolymers were synthesized via the radical (co)­polymerization of 4-bromophenyl vinyl sulfide (BPVS) and styrene (St) followed by oxidation of the thus-produced sulfides, P­(BPVS) and P­(BPVS-r-St)­s, to the corresponding sulfones and Pd-catalyzed coupling with phenoxazine-substituted phenyl boronate ester (PXZPhBpin) to afford P­(PVSO2-PhPXZ) and P­(PVSO2-PhPXZ-r-St)­s, respectively. The prepared homo- and copolymers, featuring a π-conjugated phenylene unit between the electron-accepting sulfone (SO2) unit and the electron-donating phenyl phenoxazine (PhPXZ) unit in their side chains, exhibited thermally activated delayed fluorescence (TADF) and were used to fabricate organic light-emitting diodes (OLEDs). The device with spin-coated P­(PVSO2-PhPXZ) as an emitting layer showed a maximum external quantum efficiency (EQEmax) of 1.0%, whereas that with an emitting layer of spin-coated 75 mol %-St P­(PVSO2-PhPXZ-r-St) exhibited efficient bluish-green emission with EQEmax = 4.1%. The presented design strategy allows one to manipulate the polarity and electrochemical properties of pendant units as well as design molecular structures with suitable spacers between donor and acceptor units in the TADF side chain, thus helping to achieve the desired (opto)­electronic properties. Thus, this work significantly extends the range of nonconjugated TADF polymers and paves the way for the fabrication of next-generation OLEDs.

Benzonitrile-based AIE polymer host with a simple synthesis process for high-efficiency solution-processable green and blue TADF organic light emitting diodes

“…Although some small molecular host materials suitable for vacuum evaporation have been reported for TADF emitters, developing an efficient polymer host for solution-processed TADF devices is still a big challenge. [4][5][6][7][8] To be an excellent host for the TADF emitter, the compound generally needs a higher E T to confine the exciton, a suitable frontier orbital to match the carrier injection potential, and a sufficient PL overlap with the absorption of the emitter to ensure the energy transfer. 9,10 Based on the above strategies, many small molecule TADF host materials have been designed for high-efficiency OLEDs.…”

Polymers fromS-vinyl monomers: reactivities and properties

“…The free-radical polymerizations of vinyl sulfide derivatives lead to polymers with very high molar masses and also prove to be faster compared to their oxygen analogues, provided that the suitable initiators are used, for example azo initiators such as azobisisobutyronitrile (AIBN). 31,[35][36][37][38][39][40][41][42][43] Peroxides, on the other hand, appear not to be suitable for polymerization, since the oxidation of the sulfide to the corresponding sulfoxide or sulfone is preferred. 44 The increased reactivity of vinyl sulfides compared to vinyl ethers was demonstrated early on and already explained by Price and coworkers in 1950, 36 who observed a bathochromic shift when unsaturated sulfide molecules were excited with light compared to saturated ones.…”

Dual-State Emission (DSE) in Organic Fluorophores: Design and Applications

“…This set of characteristics may lead to better processability of these compounds, looking for complementary applications. For instance, organic compounds that have shown fluorescence in solution are now being used in medicine (i.e., bioimaging) − or materials chemistry (i.e., sensors). − Furthermore, solid organic emitters are now being used as active layers in organic light-emitting diodes (OLEDs), − solar cells, or even supramolecular encryption systems (Figure ). To attain a more comprehensive perspective, the reader is referred to excellent reviews focusing on compounds emissive in a single state, either in solution or in the solid, in the form of aggregates or crystalline materials. − …”