Tetra-Donor Pyrazine based Thermally Activated Delayed Fluorescence Emitters for Electroluminescence and Amplified Spontaneous Emission

Thermally activated delayed fluorescence (TADF) materials are expected to address triplet-related losses in electrically driven organic lasers, as the electrically generated triplets in the materials can be converted to radiative singlets through reverse intersystem crossing (RISC). This offers a way to bypass triplet absorption and annihilation in organic semiconductor lasers (OSLs). In this work we present two versatile TADF emitters 4tCzPz and 4αCbPz for application in OLEDs and OSLs. Both emitters possess moderately high ΔEST (~0.30 eV) and show high ΦPL in solution and solid state and prominent stimulated emission features in solution. Films of 4tCzPz and 4αCbPz doped in mCBP show an amplified spontaneous emission (ASE) threshold of 41.0 and 44.9 µJ/cm2, respectively. The OLEDs with 4tCzPz and 4αCbPz emitted with peak wavelengths of 492 nm and 475 nm, respectively, and showed corresponding maximum external quantum efficiencies, EQEmax, of 24.6 and 21.3%. Our research shows that D-A TADF materials hold significant potential not only as emitters for OLEDs but also in OSLs.