Thermally Activated Delayed Fluorescence
In 1987, Tang and Von Slyke discovered organic light emitting diodes (OLEDs) which have great display qualities, thin and light structures. These OLED materials have improved applications in display and lighting technology. However, OLED devices have some insufficiencies which require further improvement. Economy and availability are the most important points in their applications. Synthesized OLEDs’ low device performances encouraged scientists to design a red color emitting OLED device by organometallic complexes. However, although the efficiency was increased up to maximum levels, their applications were limited due to toxicity of heavy metals and their high prices. While OLED based thermally activated delayed fluorescence (TADF) materials were designed and their popularities have increased within the years. These materials work with reverse intersystem crossing (RISC) process between triplet and singlet excited states. In order to obtain high efficiency RISC, designed materials should have appropriate physical properties.
In our research we mainly study the excited state characteristics of these materials to improve structure-performance relationships in device applications. We perform TD-DFT, CAS-SCF and CAS-PT2 calculations to determine their photophysical characteristics clearly. The main goal is to gain insight into the factors affecting their efficiency which will allow the design of new TADF molecules.