<p>The molar extinction coefficient (<i>ε</i>) is a fundamental physical parameter for optoelectronic molecules, critically determining the energy conversion efficiencies of corresponding devices. Benefiting from strong intramolecular resonance enabled by donor-acceptor (D-A) structural modulation, merocyanine dyes are capable of delivering large <i>ε</i> at relatively low molecular weights. Such resonance originates from the equilibrium between neutral and zwitterionic resonance forms, whose magnitude can be quantitatively evaluated using the resonance coefficient <i>c</i>². Specifically, a <i>c</i>² of 0.5 corresponds to ideal strong resonance and superior photophysical performance. Herein, two D-<i>π</i>-A emitters, namely N-O-2CN and N-S-S, were rationally developed. Both molecules possess prominent two-state resonance characteristics, with calculated <i>c</i>² values of 0.44 and 0.45, respectively. Consistently, the two compounds display outstanding molar absorptivity: N-O-2CN affords a maximum <i>ε</i> of 6.43×10⁴ L·mol⁻¹·cm⁻¹ at 468 nm. More impressively, N-S-S reaches an exceptionally high <i>ε</i> of 1.23×10⁵ L·mol⁻¹·cm⁻¹ at 509 nm while bearing a low molecular weight of merely 377, which facilitates favorable processing capability. In addition, N-O-2CN and N-S-S exhibit narrowband blue and green luminescence, with full-width-at-half-maximum of 0.26 eV at 491 nm and 0.20 eV at 532 nm, respectively.</p>