Electron-Rich Cores Empower Organic C-Shaped Dyes With Emission Peaking Around 1000 nm, 14.3% PLQY, and >3% EQE in OLEDs.

We establish a molecular design blueprint for highly emissive, metal-free organic NIR emitters by integrating an electron-rich S,N-heteroacene core into a C-shaped architecture, affording CT-F, and further extending this framework through selenium incorporation to generate the S,Se,N-heteroacene-based CT-Se and CT-2Se. This molecular architecture synergistically enhances intramolecular charge transfer (ICT) while suppressing internal reorganization energy through increased molecular rigidity. The optimized CT-F dye achieves a solid-state photoluminescence quantum yield of 14.3% at 970 nm. Incorporation of CT-Se into a hyperfluorescent OLED employing a transfer-printed sensitizer and balanced charge injection yields an external quantum efficiency (EQE) of 3.07% at 1000 nm, whereas introducing an additional PM6 buffer layer enables relay-type interfacial energy transfer, elevating the EQE to 3.56% at 995 nm. Comprehensive mechanistic studies reveal that electron-rich core-driven ICT modulation, molecular rigidification with controlled stacking, asymmetric vibronic coupling regulation, and balanced intrinsic charge transport cooperatively establish an omnidirectional optimization strategy for achieving high-efficiency organic OLEDs peaking around 1000 nm and extending into the NIR-II region.