Fully RoHS Compliant Infrared Light Emitting Diodes Based on Novel Lead-free Quantum Dots

Project Information

INFLED

Grant agreement ID: 101024823

DOI

10.3030/101024823

Project closed

EC signature date 13 April 2021

Start date 1 April 2022

End date 31 March 2024

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 171 473,28

EU contribution

€ 171 473,28

Coordinated by

FONDAZIONE ISTITUTO ITALIANO DI TECNOLOGIA
Italy

Periodic Reporting for period 1 - INFLED (Fully RoHS Compliant Infrared Light Emitting Diodes Based on Novel Lead-free Quantum Dots)

Reporting period: 2022-04-01 to 2024-03-31

Summary of the context and overall objectives of the project

Infrared light-emitting diodes (IR-LEDs) technology serves a wide range of applications, including fiber-optic communication, biomedical imaging, security, and night vision. Despite the significant potential of lead-containing colloidal semiconductor quantum dots in advancing IR-LED technology due to their cost-effectiveness and distinct optical properties, their development is significantly hindered by the toxicity of lead.

The EU-funded INFLED project addressed the need for novel and efficient lead-free quantum dots. This was crucial as traditional quantum dots often contained heavy metals, posing environmental and health risks. The project was significant for society as it aimed to develop highly efficient, heavy metal-free infrared LEDs, which could lead to safer and more sustainable lighting technologies. Overall, the project's objectives included pioneering a novel synthesis technique and employing rational nanoengineering in both material and device levels, ultimately contributing to cleaner and more efficient lighting solutions.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

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.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The INFLED project represents a significant advancement in the field of near-infrared light-emitting diodes (NIR LEDs) by introducing efficient, stable, and fully RoHS-compliant NIR LEDs based on colloidal indium arsenide semiconductor quantum dots (QDs). Unlike traditional semiconductor quantum dots, which consist of toxic elements such as lead or cadmium, our approach utilizes lead-free colloidal QDs. This innovation not only addresses environmental concerns associated with hazardous materials but also opens up new possibilities for the development of sustainable and environmentally friendly lighting technologies.

The NIR LEDs developed under the INFLED project demonstrate a record external quantum efficiency of 5.5% at 947 nm, surpassing previous benchmarks in NIR QDLED efficiency. Additionally, the operational lifetime of these LEDs extends to approximately 32 hours before reaching 50% of their initial luminance, indicating remarkable stability compared to existing alternatives. By achieving these unprecedented performance metrics, the INFLED project paves the way for the widespread adoption of RoHS-compliant light-emitting technologies in various applications, from consumer electronics to medical devices and beyond. Overall, the INFLED project represents a crucial step towards a cleaner, greener, and more technologically advanced future.

NIR QD LEDs based on indium arsenide quantum dots