Prying into the limit of CIE value for TPE-based blue AIEgens in organic light-emitting diodes

• By incorporating tetraphenylethene (TPE) into the polyphenylbenzene platform, four highly twisted AIEgens were synthesized.
• All compounds exhibited typical AIE phenomenon.
• OLED devices utilizing these compounds showed blue to deep-blue emission.
• For the first time, limit value of CIE for TPE-containing AIEgens was investigated.

By incorporating tetraphenylethene (TPE) into the platform of polyphenylbenzene through different linkage modes and adjustment of conjugation, four highly twisted luminogens were synthesized, of which showed good thermal stability verified by thermogravimetric and differential scanning calorimetry analysis. All these luminogens exhibited typical aggregation induced emission phenomenon. Utilizing them as emitting layers, nondoped fluorescent organic light-emitting diodes were fabricated. Thanks to their well-designed highly twisted structures, all devices showed blue to deep-blue emission. The deep-blue emission devices based on emitter containing meta-tetraphenylethene exhibited maximum current efficiency of 1.32 cd A−1, while the Commission Internationale de l'Éclairage (CIE) coordinates were (0.16, 0.12), close to our previous report of deep-blue emission. Combined with our previous results, it might be predicted that perhaps, the CIE coordinates limit of TPE-based luminogens should be around (0.15, 0.11), and the CIEy is hard to break through 0.10, unless other building blocks with shorter conjugation used instead of TPE.

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