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

Luo, Y., Zhang, K., Ding, Z. et al.

Nat Commun 13, 6892 (2022).

https://doi.org/10.1038/s41467-022-34573-2

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’ T1 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’ T1 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.

Angle-dependent photoluminescence was measured to obtain the horizontal dipole ratio (HDR, Θ//) of the light emission molecules in neat film state. p-polarized angle-dependent light emissions of films were measured by Fluxim. The HDR of thin films and light out-coupling efficiency of devices were then simulated by Setfos.