Efficient Organic Light-Emitting Diodes from Delayed Fluorescence

During the last two decades, organic light-emitting diodes (OLEDs) have received a greatdeal of attention as a solution for high-resolution and large area flat display panels [1]. The goalof this project is to predict the absorption wavelengths and the emission of fluorescence diodeswith a delayed active heat. Calculations are done using the ORCA software [2]. The first step inthe calculation of the time dependent density functional of the theory (TD-DFT) is on the desireddioniode. In this study, important transfers and involved orbitals are identified. In the next step,using the CASSCF/NEVPT2 calculations, the energy of the transmissions is determined. Finally,the new diodes are suggested by adding different substitutes and studying the absorption andemission wavelengths. It should be noted that the three essential requirements for an OLEDTADFare as follows : (A) There is a small energy gap between the excited states S1 and T1 (lessthan 0.2 electron volts)(B) Small Exchange Integral between HOMO and LUMO orbital(C) The separation and centralization of HOMO or LUMO orbitalThe mechanism of action in thermally activated delayed fluorescence (TADF) is that: Asstated in the mandatory clause of a TADF, the difference in energy between the lower energy level T1and the higher energy level S1 shall be sufficiently small to permit reverse intersection system (RISC) tobe carried out at ambient temperature (T1 → S1). The energy difference between these two levels isproportional to the energy converted, which is related to the overlap integral between the two orbital onesresponsible for the states of the two levels. When the energy gap between the two T1 and S1 levels issubjected to thermal energy (about 26 mV at room temperature), the reverse cross-system through heatexcitation and stimulation will occur far more and the fluorescence in this case The delayed fluorescenceis known to occur from the S1 level [3].

Keywords:

OLEDs , TDDFT , TADF , HOMO , LUMO