Periodic Reporting for period 1 - NIRLUMIN (RoHS compliant, high luminescence, heterostructure nanocrystals for near infrared LEDs and bioimaging.)
Okres sprawozdawczy: 2023-06-01 do 2025-05-31
Context and Motivation
The research towards the advancement of semiconductor quantum dots (QDs) that are efficient emitters in the near-infrared (NIR) or short-wave infrared (SWIR) region are of paramount importance for NIR-based technologies, including biomedical imaging, telecommunications, night-vision sensors, health monitoring food inspection, and energy-efficient lighting. However, most of the efficient NIR-emitting QDs reported, rely on toxic heavy metals like lead (Pb) and mercury (Hg), which are restricted under the European Restriction of Hazardous Substances (RoHS) directive. This regulatory constraint, combined with growing environmental and health concerns, has created an urgent need for RoHS-compliant, high-performance alternatives that match or surpass the optical properties of Pb/Hg-based QDs.
Existing heavy-metal-free alternatives, such as I-III-VI (e.g. CuInS2, AgInSe2) and III-V (e.g. InAs) QDs, suffer from key limitations:
• Low photoluminescence quantum yield (PLQY) beyond 1000 nm.
• Broad emission linewidths (>150 meV), reducing spectral precision.
• Limited tunability across the SWIR range (1000–1400 nm).
This project, NIRLUMIN, addresses these challenges by developing novel heterostructured QDs based on I-III-VI, Cu-Zn-In-Se (CZISe) with engineered shells (ZnS/Al2O₃) to achieve high efficiency, narrow emission, and environmental stability—while remaining fully RoHS-compliant.
Overall Objectives
The project’s primary goal was to design, synthesize, and optimize heavy-metal-free efficient NIR-emitting QDs as a potential alternative to the Pb/Hg-based QDs. Specific objectives included:
• Synthesis and development of I-III-VI-based QDs via partial cation exchange, enabling precise control over morphology (triangular, spherical, cubic) and size.
• Enhancement of optical properties and stability through core-shell engineering targeting: high PLQY, tunable emission beyond 1000 nm with narrow emission linewidth and long term stability.
• For biocompatibility, encapsulate the core-shell QDs with a ceramic-type shell of alumina (Al2O3) to provide further passivation and prevent degradation of the nanocrystals in different environments as well as the associated leaching out of metal ions, which can have toxic effects (e.g. zinc).
• Surface functionalization for compatibility with optoelectronic devices (LEDs, sensors) and biomedical applications (aqueous dispersion).
• Proof-of-concept integration into NIR-LEDs and down-conversion systems.
The research towards the advancement of semiconductor quantum dots (QDs) that are efficient emitters in the near-infrared (NIR) or short-wave infrared (SWIR) region are of paramount importance for NIR-based technologies, including biomedical imaging, telecommunications, night-vision sensors, health monitoring food inspection, and energy-efficient lighting. However, most of the efficient NIR-emitting QDs reported, rely on toxic heavy metals like lead (Pb) and mercury (Hg), which are restricted under the European Restriction of Hazardous Substances (RoHS) directive. This regulatory constraint, combined with growing environmental and health concerns, has created an urgent need for RoHS-compliant, high-performance alternatives that match or surpass the optical properties of Pb/Hg-based QDs.
Existing heavy-metal-free alternatives, such as I-III-VI (e.g. CuInS2, AgInSe2) and III-V (e.g. InAs) QDs, suffer from key limitations:
• Low photoluminescence quantum yield (PLQY) beyond 1000 nm.
• Broad emission linewidths (>150 meV), reducing spectral precision.
• Limited tunability across the SWIR range (1000–1400 nm).
This project, NIRLUMIN, addresses these challenges by developing novel heterostructured QDs based on I-III-VI, Cu-Zn-In-Se (CZISe) with engineered shells (ZnS/Al2O₃) to achieve high efficiency, narrow emission, and environmental stability—while remaining fully RoHS-compliant.
Overall Objectives
The project’s primary goal was to design, synthesize, and optimize heavy-metal-free efficient NIR-emitting QDs as a potential alternative to the Pb/Hg-based QDs. Specific objectives included:
• Synthesis and development of I-III-VI-based QDs via partial cation exchange, enabling precise control over morphology (triangular, spherical, cubic) and size.
• Enhancement of optical properties and stability through core-shell engineering targeting: high PLQY, tunable emission beyond 1000 nm with narrow emission linewidth and long term stability.
• For biocompatibility, encapsulate the core-shell QDs with a ceramic-type shell of alumina (Al2O3) to provide further passivation and prevent degradation of the nanocrystals in different environments as well as the associated leaching out of metal ions, which can have toxic effects (e.g. zinc).
• Surface functionalization for compatibility with optoelectronic devices (LEDs, sensors) and biomedical applications (aqueous dispersion).
• Proof-of-concept integration into NIR-LEDs and down-conversion systems.
Work Performed and Main Achievements
Synthesis & Material Development:
Materials development 1: Developed triangular shapes CZISe/ZnS nanocrystals via partial cation exchange: In this work we have used cation exchange (CE) or template synthesis technique which offers more precise control over size and shape resulting in long range emission tunability. In2Se3 seeds were synthesized by hot injection technique, followed by the addition of Cu precursor and Zinc precursor successively and annealing at higher temperature led to the formation of Cu-In-Se by partial cation exchange. Finally, ZnS was over coated to passivate the surface and improve the PLQY. Main achievements are
o Maximum PLQY 40%
o Tunability from 1080 nm to 1220 nm.
o Narrow PL linewidth (FWHM: 102–122 meV).
Materials development 2: Developed a novel synthesis technique for CZISe/ZnS/Al2O₃ core-shell-shell QDs with cubical and spherical morphologies Starting with Cu2₋ₓSe seeds, we synthesized CZISe via partial cation exchange of Cu with In and Zn. This was followed by the growth of ZnS and Al2O₃ shells, enhancing PLQY, environmental stability, and biocompatibility. Main achievements are
o RoHS compliant NIR emitting engineered CZISe/ZnS/Al2O₃ core-shell-shell QDs.
o Record 53.5% PLQY at 1036 nm in this type of QDs
o Wide range of tunability tunability from 915–1320 nm by exploiting the quantum confinement effect.
o Narrow Pl linewidth (lowest observed-102 meV)
o Long term optical stability (more than 9-month) under ambient conditions
Functionalization & Integration:
• Successfully exchanged organic ligands with short-chain iodides for DMF solubility (potential for ink-based devices).
• Demonstrated down-conversion in polymer matrices for NIR-LED prototypes (optimization needed)
Synthesis & Material Development:
Materials development 1: Developed triangular shapes CZISe/ZnS nanocrystals via partial cation exchange: In this work we have used cation exchange (CE) or template synthesis technique which offers more precise control over size and shape resulting in long range emission tunability. In2Se3 seeds were synthesized by hot injection technique, followed by the addition of Cu precursor and Zinc precursor successively and annealing at higher temperature led to the formation of Cu-In-Se by partial cation exchange. Finally, ZnS was over coated to passivate the surface and improve the PLQY. Main achievements are
o Maximum PLQY 40%
o Tunability from 1080 nm to 1220 nm.
o Narrow PL linewidth (FWHM: 102–122 meV).
Materials development 2: Developed a novel synthesis technique for CZISe/ZnS/Al2O₃ core-shell-shell QDs with cubical and spherical morphologies Starting with Cu2₋ₓSe seeds, we synthesized CZISe via partial cation exchange of Cu with In and Zn. This was followed by the growth of ZnS and Al2O₃ shells, enhancing PLQY, environmental stability, and biocompatibility. Main achievements are
o RoHS compliant NIR emitting engineered CZISe/ZnS/Al2O₃ core-shell-shell QDs.
o Record 53.5% PLQY at 1036 nm in this type of QDs
o Wide range of tunability tunability from 915–1320 nm by exploiting the quantum confinement effect.
o Narrow Pl linewidth (lowest observed-102 meV)
o Long term optical stability (more than 9-month) under ambient conditions
Functionalization & Integration:
• Successfully exchanged organic ligands with short-chain iodides for DMF solubility (potential for ink-based devices).
• Demonstrated down-conversion in polymer matrices for NIR-LED prototypes (optimization needed)
The NIRLUMIN achieved breakthroughs that significantly advance the field of heavy-metal-free QDs for SWIR applications. Prior state-of-the-art I-III-VI-based QDs (e.g. CuInS2, AgInSe2, CuInSe2) or their heterostructures struggled with low PLQY (beyond 1000 nm), broad PL-linewidths (FWHM>200 meV), and limited spectral tunability. CZISe/ZnS triangular nanocrystals with 40% PLQY beyond 1000 nm and exceptionally narrow emission (FWHM: 102–122 meV), rivaling even toxic InAs QDs. Further development of the CZISe/ZnS/Al2O₃ core-shell-shell QDs, which set a new benchmark with 53.5% PLQY at 1036 nm—the highest reported for I-III-VI-based QDs in this spectral range (beyond 1000 nm)—along with unprecedented tunability (915–1320 nm). The alumina (Al2O₃) shell also enabled over 9-month stability under ambient conditions, solving a critical degradation problem in prior work.
By overcoming the traditional trade-offs between performance, toxicity, and stability, NIRLUMIN’s QDs bridge the gap between research and industrial adoption, offering a viable alternative for next-generation optoelectronics, biomedical imaging, and EU-regulated technologies.
By overcoming the traditional trade-offs between performance, toxicity, and stability, NIRLUMIN’s QDs bridge the gap between research and industrial adoption, offering a viable alternative for next-generation optoelectronics, biomedical imaging, and EU-regulated technologies.