Near-Infrared Light-Emitting Diodes With 15.8% External Quantum Efficiency via Electron-Phonon Coupling Regulation in Eco-Friendly CuInSSe/ZnS Quantum Dots

Despite their eco-friendly profile, the luminescence efficiency of I–III–VI group quantum dots (QDs) for near-infrared (NIR) applications is fundamentally limited by defects and strong electron-phonon coupling (EPC). Here, we report a solvent engineering strategy that simultaneously regulates the composition and defect states in CuInSSe QDs by tuning the DDT/ODE ratio. This approach effectively mitigates EPC, reducing the Huang–Rhys factor from 6.2 to 1.2 and boosting the photoluminescence quantum yield (PLQY) to 56.4%. Subsequent ZnS shell coating further elevates the PLQY to 93.9%. Temperature-dependent spectroscopy and theoretical calculations suggest that defect suppression plays a significant role in weakening EPC. Based on these QDs, we fabricated near-infrared quantum dot light-emitting diodes (NIR-QLEDs) exhibiting an average external quantum efficiency (EQE) of 15.8±1.3% (20 devices) and a maximum EQE of 18.5% at 910 nm, which is one of the highest values reported for CuInSSe-based NIR-QLEDs to date, along with a peak radiance of 7.8 W sr −1 m −2 . We further demonstrate their potential in non-invasive bio-imaging. This work provides a viable path to high-performance eco-friendly optoelectronics by manipulating fundamental electron-phonon interactions.