OLEDs are an important innovation in lighting markets, providing improved image quality, high brightness, low fabrication costs, low power consumption and high durability. After significant efforts on increasing device efficiencies of OLEDs, thermally activated delayed fluorescence (TADF) materials have attracted great attention as they harvest both singlet and triplet states without using any heavy metals.
The TADF phenomenon is based on the upconversion from the triplet (T1) to singlet (S1) states due to sufficiently small energy gap (ΔES-T) (<0.1 eV), facilitating the reverse intersystem crossing process (RISC). To possess such an effective charge transfer, systems should contain spatially separated highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) states as a result of a twisted molecular structure, that leads to small ΔES-T gap.
We use quantum chemical calculations to propose a new strategy on material design and investigate the relationship between molecular structures and the photophysical properties of a range of emitters. This study is in collaboration with Assoc. Prof .S. Catak (BU) and A. Monari (ULorraine).