Exploiting narrow-bandwidth-emission fluorescent materials is crucial for next-generation wide-color gamut displays. Inspired by the narrow-bandwidth-emission characteristic of chlorophyll derivates, the present work develops a facile strategy to synthesize a series of red-emitting chlorophyll-structured CDs (CHL-CDs) with ultra-high color purity and good carrier mobility from different traditional Chinese medicine leaves through a simple cross-linking polymerization and carbonization process. The obtained CHL-CDs exhibit bright photoluminescence centered at 671 nm, ultra-high color purity with an FWHM of 23 nm, and a high photoluminescence quantum yield of up to 62%. More importantly, based on in-depth experimental and theoretical studies on the macroscopic host-guest interactions and microscopic interfacial interactions between the CHL-CDs and charge transporting materials, high-performance red electroluminescent light-emitting diodes are successfully prepared, with FWHM of only 28 nm, turn-on voltage of 3.7 V, maximum luminance of 623 cd m, and maximum current efficiency of 0.26 cd A. This study provides a universal platform for fabricating narrow-bandwidth-emission CDs with significant applications in photoelectric devices.