Ultra-fast triplet-triplet-annihilation-mediated high-lying reverse intersystem crossing triggered by participation of nπ*-featured excited states

作者：Luo, Yanju; Zhang, Kai; Ding, Zhenming; Chen, Ping^*; Peng, Xiaomei; Zhao, Yihuan; Chen, Kuan; Li, Chuan; Zheng, Xujun; Huang, Yan; Pu, Xuemei; Liu, Yu^*; Su, Shi-Jian^*; Hou, Xiandeng; Lu, Zhiyun^*

来源：Nature Communications, 2022, 13(1): 6892.

DOI：10.1038/s41467-022-34573-2

• LIGHT-EMITTING-DIODES
• UP-CONVERSION
• MAGNETO-ELECTROLUMINESCENCE
• FLUORESCENCE
• EFFICIENT
• SINGLET
• EMISSION
• EMITTERS
• FUSION
• OLEDS

The harvesting of 'hot' triplet excitons through high-lying reverse intersystem crossing mechanism has emerged as a hot research issue in the field of organic light-emitting diodes. However, if high-lying reverse intersystem crossing materials lack the capability to convert 'cold' T-1 excitons into singlet ones, the actual maximum exciton utilization efficiency would generally deviate from 100%. Herein, through comparative studies on two naphthalimide-based compounds CzNI and TPANI, we revealed that the 'cold' T-1 excitons in high-lying reverse intersystem crossing materials can be utilized effectively through the triplet-triplet annihilation-mediated high-lying reverse intersystem crossing process if they possess certain triplet-triplet upconversion capability. Especially, quite effective triplet-triplet annihilation-mediated high-lying reverse intersystem crossing can be triggered by endowing the high-lying reverse intersystem crossing process with a (3)pi pi*->(1)n pi* character. By taking advantage of the permanent orthogonal orbital transition effect of (3)pi pi*->(1)n pi*, spin-orbit coupling matrix elements of ca. 10 cm(-1) can be acquired, and hence ultra-fast mediated high-lying reverse intersystem crossing process with rate constant over 10(9) s(-1) can be realized. @@@ Here, the authors investigate naphthalimide-based compounds with cold triplet excitons utilized by triplet-triplet annihilation-mediated high-lying reverse intersystem crossing, and realize rate constant of over 10(9) s(-1) with exciton utilization efficiency of 46.7% in organic light-emitting diodes.

• 单位
  四川大学; y; 西南大学