Herein the novel tetraphenylethylene (TPE) derivative 1 was designed with an integration of aggregationinduced emission (AIE), multi-state mechanochromism and self-recovery photochromism. The molecule was susceptible to grinding,heating and vapor fuming and showed corresponding transition of its emission colors.T he heated powder or single crystal of 1 exhibited reversible photochromism. After ashort period of UV irradiation, it showed ab right red color,b ut recovered to its original white appearance within 1min. The photochromism is due to the formation of photocyclization intermediates upon UV irradiation, while the eversible mechanochromism is attributed to the weak molecular interactions derived from head-to-tail stacking of the molecules.T his reversible multi-state,h igh-contrasted and rapid responsive mechanochromic and photochromic property cooperatively provided ouble enhancement of am ultimode guarantee in advanced anti-counterfeiting.

Persistent luminescence is a fascinating phenomenon with exceptional applications. However, the development of organic materials capable of persistent luminescence, such as organic persistent room-temperature phosphorescence, lags behind for their normally low efficiency. Moreover, enhancing the phosphorescence efficiency of organic luminophores often results in short lifetime, which sets an irreconcilable obstacle. Here we report a strategy to boost the efficiency of phosphorescence by intramolecular triplet-triplet energy transfer. Incorpotation of (bromo)dibenzofuran or (bromo)dibenzothiophene to carbazole has boosted the intersystem crossing and provided an intramolecular triplet-state bridge to offer a near quantitative exothermic triplet–triplet energy transfer to repopulate the lowest triplet-state of carbazole. All these factors work together to contribute the efficient phosphorescence. The generation and transfer of triplet excitons within a single molecule is revealed by low-temperature spectra, energy level and lifetime investigations. The strategy developed here will enable the development of efficient phosphorescent materials for potential high-tech applications.

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