High-Performance Non-doped Blue OLEDs based on Efficiently Triplet-Triplet Upconversion and Aggregation-induced Emission

Triplet-triplet upconversion (TTU), where two low-energy triplet excitons are converted to one higher energy singlet exciton, is excellent approach to break through the theoretical limit of the pure fluorescent organic light-emitting diodes (OLEDs) by 5%. To data, however, the reported emitters with high emission efficiency and efficiently TTU in film state are rare. Herein, we design the blue aggregation-induced emission luminogens (AIEgens) and investigate their upconversion efficiency. TPA-An-mPhCz can not only achieve high emission efficiency in the film state, but also show high upconversion efficiency of close to 50% even though the calculated energy level of the triplet excitons (T₂) is lower than 2T₁. A possible upconversion mechanism is proposed according to the transient electroluminescence spectra and theoretical calculation. This strategy may provide a new platform for the construction of highly efficient non-doped blue OLEDs based on TTU and AIEgens.

High-Performance Non-doped Blue OLEDs based on Efficiently Triplet-Triplet Upconversion and Aggregation-induced Emission

Triplet-triplet upconversion (TTU), where two low-energy triplet excitons are converted to one higher energy singlet exciton, is excellent approach to break through the theoretical limit of the pure fluorescent organic light-emitting diodes (OLEDs) by 5%. To data, however, the reported emitters with high emission efficiency and efficiently TTU in film state are rare. Herein, we design the blue aggregation-induced emission luminogens (AIEgens) and investigate their upconversion efficiency. TPA-An-mPhCz can not only achieve high emission efficiency in the film state, but also show high upconversion efficiency of close to 50% even though the calculated energy level of the triplet excitons (T₂) is lower than 2T₁. A possible upconversion mechanism is proposed according to the transient electroluminescence spectra and theoretical calculation. This strategy may provide a new platform for the construction of highly efficient non-doped blue OLEDs based on TTU and AIEgens.

GEODYNAMICS

The dependence of the temporal parameters of the energy of the earthquake accelerograms and hypocentral distance. The conclusions about the need to consider the temporal characteristics of the original scaling accelerograms for the earthquake calculated energy level.