Chitose Youhei, Mageswari Gomathi Vinayakam, Zenke Ryota, Ide Toshiharu, Kohata Shintaro, Lin Ja-Hon, Lin Tzu-Chau, Tsuchiya Youichi, Adachi Chihaya
Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka, 819-0395, Japan.
Department of Applied Chemistry, Kyushu University, 744 Motooka, Nishi, Fukuoka, 819-0395, Japan.
Adv Mater. 2025 Jul 29:e2509857. doi: 10.1002/adma.202509857.
The simultaneous realization of two-photon absorption (2PA) and thermally activated delayed fluorescence (TADF) in a single molecular system remains challenging due to an inherent trade-off in their molecular design requirements. In this study, we present a strategy to enhance both properties by introducing electron-withdrawing substituents into the CzTRZ scaffold, thereby leveraging an electron-withdrawing-enhanced intramolecular charge transfer (EWICT) character. The incorporation of TRZCF and TRZCN units effectively enhances the charge transfer (CT) character of CzTRZ, resulting in high 2PA cross-sections (156 GM for CzTRZCF and 200 GM for CzTRZCN) and a reduced singlet-triplet energy gap (ΔE = E - E). Computational and experimental studies reveal that incorporating TRZCF and TRZCN units selectively stabilizes the S state and reduces ΔE, significantly facilitating the reversed intersystem crossing (RISC) process. Notably, 1c exhibits the fastest RISC rate (k), leading to superior TADF properties and an external quantum efficiency (EQE) of 13.5% in OLEDs. Moreover, a relatively high two-photon brightness of 174 GM is estimated for 1c. 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.
