Boosting the efficiency of organic persistent room-temperature phosphorescence by intramolecular triplet-triplet energy transfer

Abstract

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.

Design of highly efficient deep-blue organic afterglow through guest sensitization and matrices rigidification

“…1d, e). To the best of our knowledge, both the lifetime and PhQY are among the highest ones of OURTP [29][30][31] , let alone the hardly available deep-blue organic afterglow (Supplementary Table 1, Supplementary Note 1 and Supplementary Figs. 2-4) 26 .…”

Ultralong lifetime and efficient room temperature phosphorescent carbon dots through multi-confinement structure design

“…Furthermore, the resultant CDs@SiO 2 phosphors present very high absolute PQE of over 21% with ultralong lifetime (up to 5.72 s) simultaneously. The maximum absolute PQE of the resultant multi-confined RTP CDs@SiO 2 reached 26.36%, which is much higher than most of the previously reported metal-free RTP phosphors of CDs in various matrices [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][38][39][40][41][42][43] and organic RTP materials [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]43,[48][49][50][51] (Table S2). The high PQE may also be due to the special MCE.…”

Thermally activated triplet exciton release for highly efficient tri-mode organic afterglow

“…Thus, organic afterglow efficiency is doomed to be low, considering that only a small part of photoexcited singlet excitons can be transformed to triplet ones through ISC under weak SOC values of purely organic molecules and the nonradiative transitions dominate the triplet exciton decay with the low phosphorescence efficiency at room temperature 8 . Many efforts have been devoted to address this issue, ranging from promoting the ISC process to efficiently populate T 1 and T 1 *,11 , enhancing the intra/ intermolecular interactions to suppress the nonradiative transition 12,13 , to incorporating heavy atoms to facilitate both SOC and ISC rates for emission and exciton transformation [13][14][15][16][17] . But, very few attempts succeed in increasing organic afterglow efficiency to 10%, especially in heavy-atom-free molecules 18,19 ( Supplementary Fig.…”