High-performance organic light-emitting diodes (OLEDs) have been a subject of extensive research both in academia and in industry for the last two decades [1]. Pure organic thermally activated delayed fluorescence (TADF) materials have attracted world-wide attention in academic and industrial communities due to their high exciton utilization efficiency and low cost [2]. Organic materials which possess TADF characteristics are highly promising owing to their small singlet-triplet energy difference ($\Delta E_{\text{st}}$), which facilitates efficient reverse intersystem crossing (RISC). Due to the strong spin-orbit coupling effect in the phosphorescent materials, the optical radiation attenuation of the triplet excitons become possible, and the internal quantum efficiency of organic electroluminescence based on the phosphorescent materials can theoretically reach 100%. To design a novel TADF molecule, two principles should be followed. Firstly, the overlap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) should be separated by introducing large twist angles or steric hinderance to obtain a small $\Delta E_{\text{st}}$. Secondly, the HOMO and LUMO need to have partial overlap to guarantee high photoluminescence quantum yield (PLQY) [3].
In this work two naphthyridine and carbazole compounds with different alkyl substituents have been synthesized, where naphthyridine acts as an electron acceptor and carbazole as an electron donor. Their thermal, photophysical and electrochemical properties will be reported.