Two A–π–D–π–A molecules with a carbazole donor and a dicyanovinyl acceptor but differing in N-hexyl (h-CPDM) and N-isooctyl substituents (i-CPDM) were synthesized, and both of them presented remarkable dual properties of solvatochromism and mechanoresponsive luminescence (MRL) turn-on. The intrinsic intramolecular charge transfer (ICT) characteristic endowed both luminophors with a prominent solvatochromic effect, with emission color tuning from blue to orange-red by changing the solvent from nonpolar hexane to polar dimethyl sulfoxide. Meanwhile, the non-/weakly emissive original powders of h-CPDM and i-CPDM gave bright orange (610 nm) and yellow (596 nm) emission with the photoluminescence quantum yields increasing as high as 85-fold after being ground. Investigations revealed this mechanoresponsive luminescence turn-on could be ascribed to the disturbance of the π–π stacking interactions in the non-/weakly emissive J-aggregates by mechanical force. This work offers carbazole derivatives that can be used as sensitive fluorescent indicators for organic solvents and mechanical sensors.

The influences of conjugation on the third-order nonlinear optical (NLO) properties of covalent organic frameworks (COFs) provide guidelines to design the structures for desired applications.

Two slightly twisted A–π–D–π–A molecules were prepared to demonstrate that the red/near-infrared mechanoresponsive luminescence turn-on behaviors could be realized through mechanically disturbing their weakly/non-emissive metastable nanostructures, giving emissive amorphous aggregates with λ_em = 620 nm, Φ_F = 12% (h-DIPT) and λ_em = 700 nm, Φ_F = 10% (DIPT), respectively.

Thermally activated delayed fluorescence (TADF) dendrimers have received much attention in solution-processed non-doped organic light-emitting diodes. However, the study of their application as self-host materials in white organic light-emitting diodes (WOLEDs) is quite limited. In this contribution, solution-processed small-molecule WOLEDs were obtained by employing a newly designed blue TADF dendrimer bis(4-(3,6-bis(3,6-di-tert-butylcarbazol-N-yl) carbazole)phenyl)sulfone (G2) with a wide bandgap and a high triplet energy (3.0 eV) as the host and the blue-light-emitting material, combined with an orange iridium complex (bis(2-phenylbenzothiazolato) (acetylacetonate)iridium(III)) (Ir(bt)₂(acac)) as the dopant. The devices achieved a maximum external quantum efficiency of 10.1%, a maximum current efficiency of 17.69 cd A⁻¹ and CIE coordinates of (0.32, 0.33). They also exhibited stable electroluminescence spectra and low efficiency roll-off at a relatively high current density. These improved performances benefit from the advantages of the TADF dendrimer used as the host material. More importantly, the fast rate constant of Förster resonance energy transfer (K_ET > 10⁷ s⁻¹) suppressed intersystem crossing (ISC) on the G2 host from singlet to triplet states, leading to a reduced singlet density and suppressed singlet–triplet annihilation on the G2 host. Therefore, these results indicate that TADF dendrimers have a promising prospect in the application of high-performance solution-processed two complementary color WOLEDs.