One Acceptor Core, Two Bright Pathways: CF3-Substituted Triazines Achieve Highly Efficient Exciplexes through Inter- and Intramolecular Charge-Transfer

Intermolecular charge-transfer (CT)-based exciplexes provide broad design flexibility through independent donor and acceptor selection but typically suffer from intrinsically low photoluminescence quantum yields (PLQYs) due to diminished orbital overlap. In contrast, intramolecular CT systems readily achieve high PLQYs owing to more predictable orbital overlap, but they generally require laborious scaffold engineering with precise substituent tuning. Here, we show that a CF3-substituted triazine scaffold (T4) serves as a unifying design platform that enables high-efficiency emission in both regimes. With CzCF3 donors, T4-2CzCF3 and T4-3CzCF3 formed intermolecular CT exciplexes in mCBP-doped films, achieving PLQYs of 100%. Incorporation of stronger carbazole donors afforded T4-3Cz, which exhibited intramolecular CT-induced thermally activated delayed fluorescence (TADF) with equally high PLQY (100%) in both solution and thin films. Beyond these outstanding emissive properties, T4-3Cz displayed pronounced nonlinear optical responses, including a two-photon absorption cross-section (σ2) of 80 GM at 780 nm and a three-photon absorption cross-section (σ3) of 2.94×10-80 cm6 s2 at 1210 nm. These findings establish the T4 scaffold as a versatile molecular framework that simultaneously supports highly efficient intermolecular and intramolecular CT-based TADF while unlocking multiphoton absorption functionality, thereby bridging the fields of organic electronics and bioimaging.