Theoretical Study of Conversion and Decay Processes of Excited Triplet and Singlet States in a Thermally Activated Delayed Fluorescence Molecule

2017 ◽  
Vol 121 (25) ◽  
pp. 13448-13456 ◽  
Author(s):  
Qian Peng ◽  
Di Fan ◽  
Ruihong Duan ◽  
Yuanping Yi ◽  
Yingli Niu ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Delayed Fluorescence ◽  
Thermally Activated Delayed Fluorescence ◽  
Excited Triplet ◽  
Thermally Activated ◽  
Singlet States

Study of an Oxadiazole Derivative for a Blue Thermally Activated Delayed Fluorescence Emitter

2015 ◽  
Vol 15 (10) ◽  
pp. 7828-7831 ◽  
Author(s):  
Dong Yuel Kwon ◽  
Geon Hyeong Lee ◽  
Young Sik Kim
Keyword(s):  
Excited States ◽  
Energy Gap ◽  
Delayed Fluorescence ◽  
Excited Singlet ◽  
Thermally Activated Delayed Fluorescence ◽  
Excited Triplet ◽  
Thermally Activated ◽  
Donor And Acceptor ◽  
Homo And Lumo ◽  
Dft And Tddft Calculations

Novel thermally activated delayed fluorescence (TADF) materials (ACR-OXD, 2ACR-OXD) with 9,10- dihydro-9,9-dimethylacridine (ACR) as an electron donor and oxadiazole derivative (OXD) as an electron acceptor were designed and theoretically investigated for blue OLED emitter. Using DFT and TDDFT calculations, we gained the electron distribution of HOMO and LUMO and the energy of the lowest singlet (S1) and the lowest triplet (T1) excited states. In comparison with the previously reported a xanthen derivative (ACR-XTN), ACR-OXD exhibits a promising blue TADF emitter because of destabilizing the LUMO of ACR-OXD by the change of the electron accepting group and maintaining the steric hindrance between donor and acceptor moieties which lead to efficient TADF due to the small energy gap between the lowest excited singlet (S1) state and the lowest excited triplet (T1) state.

scholarly journals A Unified Framework for Photophysical Rate Calculations in TADF Molecules

2021 ◽  
Author(s):  
Leonardo Evaristo de Sousa ◽  
Piotr de Silva
Keyword(s):  
Delayed Fluorescence ◽  
Intersystem Crossing ◽  
Unified Framework ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Theoretical Approaches ◽  
Singlet States ◽  
Photophysical Behavior ◽  
Theoretical Standpoint

One of the challenges in organic light emitting diodes research is finding ways to increase device efficiency by making use of the triplet excitons that are inevitably generated in the process of electroluminescence. One way to do so is by thermally activated delayed fluorescence, a process in which singlet excitons undergo up-conversion to singlet states, allowing them to relax radiatively. The discovery of this phenomenon has ensued a quest for new materials that are able to effectively take advantage of this mechanism. From a theoretical standpoint, this requires the capacity to estimate the rates of the various processes involved in the photophysics of candidate molecules, such as intersystem crossing, reverse intersystem crossing, fluorescence and phosphorescence. Here we present a method that is able to, within a single framework, compute all these rates and predict the photophysics of new molecules. We apply the method to two TADF molecules and show that results compare favorably with other theoretical approaches and experimental results. Finally, we use a kinetic model to show how the calculated rates act in concert to produce different photophysical behavior.

scholarly journals Direct observation of intersystem crossing in a thermally activated delayed fluorescence copper complex in the solid state

2016 ◽  
Vol 2 (1) ◽  
pp. e1500889 ◽  
Author(s):  
Larissa Bergmann ◽  
Gordon J. Hedley ◽  
Thomas Baumann ◽  
Stefan Bräse ◽  
Ifor D. W. Samuel
Keyword(s):  
Solid State ◽  
Delayed Fluorescence ◽  
Average Lifetime ◽  
Intersystem Crossing ◽  
Time Resolved ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Singlet States ◽  
Time Resolved Photoluminescence

Intersystem crossing in thermally activated delayed fluorescence (TADF) materials is an important process that controls the rate at which singlet states convert to triplets; however, measuring this directly in TADF materials is difficult. TADF is a significant emerging technology that enables the harvesting of triplets as well as singlet excited states for emission in organic light emitting diodes. We have observed the picosecond time-resolved photoluminescence of a highly luminescent, neutral copper(I) complex in the solid state that shows TADF. The time constant of intersystem crossing is measured to be 27 picoseconds. Subsequent overall reverse intersystem crossing is slow, leading to population equilibration and TADF with an average lifetime of 11.5 microseconds. These first measurements of intersystem crossing in the solid state in this class of mononuclear copper(I) complexes give a better understanding of the excited-state processes and mechanisms that ensure efficient TADF.

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