Necessary and Sufficient Condition for Organic Room‐Temperature Phosphorescence from Host–Guest Doped Crystalline Systems

• Published in: Advanced optical materials Vol. 11; no. 10
• Main Authors: Demangeat, Catherine, Tang, Yipeng, Dou, Yixuan, Dale, Sherrice, Cielo, Jakob, Kim, Eunkyoung, Lee, Ha‐Jin, D'Aléo, Anthony, Hu, Bin, Attias, André‐Jean
• Format: Journal Article
• Language: English
• Published: 01.05.2023
• Subjects: host–guest doped systems; organic molecular crystals; organic room‐temperature phosphorescence; σ‐conjugation
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.202300289

Controlling and predicting the long‐lived room‐temperature phosphorescence (RTP) from organic materials are the next challenges to address for the realization of new efficient organic RTP systems. Here, a new approach is developed to reach these objectives by considering host–guest doped crystals, as well‐suited model systems in that they allow the comprehensive understanding of synergetic structural interactions between crystalline host matrices and emitting guest molecules, one of the key parameters to understand the correlation between the solid‐state organization and crystal RTP performances. Two series of σ‐conjugated donor/acceptor (D‐σ‐A) carbazole‐based matrices and isomeric 1H‐benzo[f]indole‐based dopants are designed, capable of exploring a wide variety of conformations thanks to large rotational degrees of freedom provided by the σ‐conjugation. By correlating the results of single‐crystal X‐ray diffraction analysis and photoluminescence properties, a necessary and sufficient condition for RTP is established that paves the way for the development of new long‐lived RTP host–guest doped systems. For achieving the long‐lived room‐temperature phosphorescence (RTP) after ceasing the light illumination of a non‐emissive carbazole‐based crystalline matrix, inserting a benzoindole‐based phosphor as dopant is not sufficient. The matrix must also display a specific crystal packing like the herringbone arrangement of the carbazole units. This result provides guidelines in terms of crystal engineering to develop new RTP host–guest doped systems.