Piezochromic luminescent and electroluminescent materials comprised of tetraphenylethene plus spirobifluorene or 9,9-diphenylfluorene

• A series of luminogens comprised of tetraphenylethene and fluorene derivatives are synthesized and characterized.
• Aggregation-induced emission is observed for the luminogens.
• Reversible piezochromic luminescence is recorded from the luminogens.
• Efficient organic light-emitting diodes are fabricated using the luminogens as host emitters.

In this work, a series of luminogens comprised of tetraphenylethene plus spirobifluorene or 9,9-diphenylfluorene are synthesized and characterized. Whereas these luminogens are weakly fluorescent in solutions, they are highly emissive in the aggregated state, with high fluorescence quantum yields up to 99% in solid films, demonstrating aggregation-induced emission characteristics. Reversible piezochromic luminescence is observed from the solids of the luminogens. A notable emission color change from blue (445 nm) to green (503 nm) is readily realized by grinding the pristine powder of the luminogen. The blue emission is recovered by fuming the ground powder with dichloromethane vapor. The undoped electroluminescence devices using the luminogens as light-emitting layers are fabricated, affording high current efficiencies up to 7.2 cd/A.

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