Enabling High‐Performance Multi‐Resonant TADF Emitters via Intramolecular Hydrogen Bond

Hydrogen bonds (HBs), prevalent strong interactions in organic compounds, can effectively constrain single bond rotation, leading to rigid planar configurations. This rigidity enhances emission efficiency and narrows the emission spectrum of luminescent materials. Recent advances have leveraged HBs to advance high‐performance donor‐acceptor thermally activated delayed fluorescence (TADF) materials. However, their application in multi‐resonance (MR) TADF emitters remains limited. We herein developed MR‐TADF emitters incorporating intramolecular hydrogen bonds (IHBs) with pyrimidine as the HB acceptor. The rigid planar conformation induced by IHBs significantly improved photoluminescence quantum yield, extended emission wavelength, reduced full‐width at half‐maximum, and decreased non‐radiative decay rates for BN‐2Pm compared to BN‐5Pm. Devices based on BN‐2Pm achieved a maximum external quantum efficiency of 36.5%, a current efficiency of 102.3 cd A−1, a power efficiency of 84.6 lm W−1, and Commission Internationale de l’Éclairage (CIE) coordinates of (0.18, 0.71). In contrast, BN‐5Pm exhibited lower values: 14.6%, 36.8 cd A−1, 27.6 lm W−1, and (0.12, 0.57), respectively.