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.