Efficient Near-Infrared Light-Emitting Diodes based on ln(Zn)As-ln(Zn)P-CaP-ZnS Quantum Dots

摘要

Near-infrared (NIR) lighting plays an increasingly important role in new facial recognition technologies and eye-tracking devices, where covert and nonvisible illumination is needed. In particular, mobile or wearable gadgets that employ these technologies require electronic lighting components with ultrathin and flexible form factors that are currently unfulfilled by conventional GaAs-based diodes. Colloidal quantum dots (QDs) and emerging perovskite light-emitting diodes (LEDs) may fill this gap, but generally employ restricted heavy metals such as cadmium or lead. Here, a new NIR-emitting diode based on heavy-metal-free In(Zn)As-In(Zn)P-GaP-ZnS quantum dots is reported. The quantum dots are prepared with a giant shell structure, enabled by a continuous injection synthesis approach, and display intense photoluminescence at 850 nm with a high quantum efficiency of 75%. A postsynthetic ligand exchange to a shorter-chain 1-mercapto-6-hexanol (MCH) affords the QDs with processability in polar solvents as well as an enhanced charge-transport performance in electronic devices. Using solution-processing methods, an ITO/ZnO/PEIE/QD/Poly-TPD/MoO3/Al electroluminescent device is fabricated and a high external quantum efficiency of 4.6% and a maximum radiance of 8.2 W sr(-1) m(-2) are achieved. This represents a significant leap in performance for NIR devices employing a colloidal III-V semiconductor QD system, and may find significant applications in emerging consumer electronic products.