Activating Intersystem Crossing and Aggregation Coupling by CN-Substitution for Efficient Organic Ultralong Room Temperature Phosphorescence

Abstract

Organic ultralong room-temperature phosphorescence (OURTP) has boomed recent advances of organic optoelectronics with the significant breakthrough in facilitating the intersystem crossing and stabilization of triplet excitons of purely organic materials. However, it remains a challenge in revealing the inherent mechanism of OURTP and the general molecular design principles of OURTP materials have yet to be reached, largely owing to the rather complicated and varied OURTP molecular structures. Here, we propose a facile strategy to design efficient OURTP materials by simply introducing a cyano group (CN) on benzene. On the basis of these very simple OURTP molecules, it was found that the simultaneously enhanced intersystem crossing and aggregation coupling are two intrinsic prerequisites in realizing the efficient OURTP. The first observation of the excimer emission from the stabilized singlet excited states offers an important evidence for the mechanism study of OURTP, and the direct CN substitution on the benzene ring would be highly instructive for designing efficient OURTP molecules.

Effect of π···π Interactions of Donor Rings on Persistent Room-Temperature Phosphorescence in D4–A Conjugates and Data Security Application

“…According to the rule, the ISC rate will be higher when either 1 ( n –π*) to 3 (π–π*) or 1 (π–π*) to 3 ( n –π*) transitions are involved, but the transition is retarded when the orbitals involved are the same in configuration ( 1 ( n –π*) to 3 ( n –π*) or 1 (π–π*) to 3 (π–π*)) . Therefore, the incorporation of heteroatoms (O, N, and S), carbonyls, and cyano groups is commonly used in the organic molecules to favor ISC. ,− In combination with this strategy, rigid host–guest matrices, crystallization, aggregation, and deuterium substitution are the key design principles to suppress the nonradiative pathways that quench triplet states.…”

Phase- and Halogen-Dependent Room-Temperature Phosphorescence Properties of Biphenylnitrile Derivatives

“…The method often adopted to suppress non-radiative transitions is to embed the phosphorescent chromophores into rigid matrixes, such as crystalline − or amorphous hosts at an appropriate concentration. − In the rigid matrix, non-radiative transition channels induced by molecular vibration can be efficiently suppressed and radiative transition turns into the dominant process. It is demonstrated that the enhanced n → π* transition can promote the ISC process, which is beneficial to the generation of efficient RTP. , The organic molecules containing heteroatoms such as O, N, and S or functional groups with lone electron pairs (aldehyde groups, carbonyl groups, CN, etc.) often exhibit n → π* transition feature, which can improve the population of triplet state excitons.…”

“…It is demonstrated that the enhanced n → π* transition can promote the ISC process, which is beneficial to the generation of efficient RTP. 33,34 The organic molecules containing heteroatoms such as O, N, and S or functional groups with lone electron pairs (aldehyde groups, 35 carbonyl groups, 36 CN, 37 etc.) often exhibit n → π* transition feature, which can improve the population of triplet state excitons.…”

Charge–Transfer Fluorescence and Room-Temperature Phosphorescence from a Bisamide-Based Derivative

“…Since then, more and more researchers have entered the field. Now, RTP can be induced by a variety of means, such as the introduction of heavy atoms, metal frames and host-guest systems, the formation of single crystals, and embedding into a polymer matrix [18][19][20][21][22].…”