Synergetic ferroelectric luminescence from self-assembled tetraphenylethene aggregates

Abstract

Synergetic ferroelectric luminescent (SFL) materials comprising a central tetraphenylethene (TP) core were synthesized by attaching TP with clipping groups (C), where clipping groups consist of a self-assembling group (SAG). TPCns selfassembled by the intermolecular interaction of SAGs to induce TP aggregation, as evidenced by the clip-induced quenching of emission at SAGs (<i>E</i>_clip) accompanied by aggregation-induced emission enhancement of TPs (<i>E</i>_AIE). TPC4 showed strong photoluminescence in a dilute chloroform solution and large <i>E</i>_AIE in aqueous (&lt;50%) THF solution. TPCn film showed SFL properties with high quantum yield of photoluminescence (&lt;80%) and ferroelectric switching. TPC4 was successfully employed in light emitting electrochemical cells (LECs) to achieve high luminance above 1290 cd m−2 under pulsed current conditions. TPC4 had a higher remnant polarization (Pr = 2.27 μC cm⁻²) at room temperature than TPC1. The thin film of TPCn was stable even with repeated bending due to the flexible SAG with long alkyl chains. Therefore, the SFL of TPCn was effectively employed in a piezoelectric nanogenerator, which produced piezoelectric output voltage of up to 0.13 V and a current density of 1.14 nA cm⁻² under repeated concave bending. These results indicate that side chain clipping and central TP aggregation resulted in unprecedented flexible SFL properties in a single compound, which simultaneously enhanced electroluminescence, mechanical sensitivity and energy harvesting ability.