The INFLED project has progressed significantly in developing efficient, stable, and environmentally friendly near-infrared light-emitting diodes (NIR LEDs) using colloidal indium arsenide semiconductor quantum dots (QDs).Throughout the project duration, key activities included:
Synthesis and Characterization of Infrared-emitting Lead-Free Colloidal QDs: We synthesized lead-free colloidal indium arsenide (InAs) semiconductor quantum dots using a commercially available tris-dimethylamino arsine (amino-As) precursor. These QDs were carefully characterized to ensure their suitability for NIR LED applications. In our synthesis, we employed a hot-injection approach using amino-As as the arsenic precursor and alane N,N-dimethylethylamine as the reducing agent, with zinc chloride as an additive. This approach improved the size distribution and photoluminescence quantum yield of the resulting indium arsenide QDs. The presence of zinc chloride facilitated the in situ growth of a zinc selenide shell on the InAs cores, resulting core/shell QDs with high photoluminescence quantum yield values of 42±4% and emission at ∼860 nm.
Device Fabrication: We fabricated NIR LEDs utilizing the synthesized QDs as the active material. Various device architectures and fabrication techniques were explored to optimize device performance. The champion device architecture comprises a thin layer (∼35 nm) of PEDOT:PSS deposited onto an indium tin oxide prepatterned substrate. A 25 nm thick poly(N,N′-bis-4- butylphenyl-N,N′-bisphenyl)benzidine layer was spin-coated on the PEDOT:PSS, thus completing the hole injection and transport side of the architecture.
Performance Evaluation: The performance of the fabricated NIR LEDs was rigorously evaluated, focusing on parameters such as external quantum efficiency, operational lifetime, and stability under different operating conditions. Thanks to the rational device design and efficient QDs, we achieved an external quantum efficiency of 5.5% and a corresponding radiance of 0.15W·sr−1·m−2 at 947 nm.
Overall, the INFLED project has achieved the following significant milestones and results: record external quantum efficiency, long operational lifetime, and RoHS compliance.
