Unlocking Dual Functionality in Triazine-Based Emitters: Synergistic Enhancement of Two-Photon Absorption and TADF-OLED Performance with Electron-Withdrawing Substituents

The simultaneous realization of two-photon absorption (2PA) and thermally activated delayed fluorescence (TADF) in a single molecular system is challenging due to the inherent trade-off in their molecular design. In this study, we develop a strategy to enhance both properties by introducing electron-withdrawing substituents into the CzTRZ scaffold. The TRZCF3 and TRZCN units effectively enhance the charge-transfer (CT) character of CzTRZ, resulting in high 2PA cross-sections (156 GM for CzTRZCF3 and 200 GM for CzTRZCN) and a reduced singlet-triplet energy gap (ΔEST = ES1 – ET1). Computational and experimental studies reveal that incorporating TRZCF3 and TRZCN units selectively stabilizes the S1 state and reduces ΔEST, significantly facilitating the reversed intersystem crossing (RISC) process. Notably, 1c exhibits the fastest RISC rate (kRISC), leading to superior TADF properties and an external quantum efficiency (EQE) of 13.5% in OLEDs. These findings demonstrate a rational molecular design strategy for the synergistic enhancement of 2PA cross-sections and excellent OLED performance, paving the way for applications in advanced imaging probes and organic semiconductors.