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Colloidal quantum dots are prized for their size-tunable optical properties and solution processability, making them attractive for next-generation displays and lighting. Among them, copper chalcogenide quantum dots - composed of earth-abundant, low-toxicity elements - stand out as a greener alternative to conventional cadmium- or lead-based materials. Yet their intrinsic copper-related vacancies and defects introduce multiple emission pathways that produce broad, impure colors, severely limiting their usefulness in display applications where color purity is paramount.
Based on these challenges, there is an urgent need for strategies that can simultaneously narrow the emission linewidth and boost the luminescence efficiency of these otherwise promising materials.
A team led by researchers at the University of Electronic Science and Technology of China, in collaboration with Panzhihua University, the Chinese Academy of Sciences, and other institutions, reports the development of high-performance, eco-friendly quantum dots for red light-emitting diodes. The findings were published (DOI: 10.1016/j.esci.2026.100536) on September, 2026, in the journal eScience (Volume 6, Issue 5, Article 100536). The work demonstrates that interfacial engineering - inserting a tailored zinc indium sulfide layer between the quantum dot core and outer shell - can effectively resolve the trade-off between brightness and color purity that has hindered copper chalcogenide quantum dots for display applications.
The team synthesized CuInGaS quantum dots with a zinc indium sulfide (ZnInS2) interfacial layer sandwiched between the core and an outer zinc sulfide shell. Transmission electron microscopy confirmed the successful growth of each layer, with the quantum dots increasing from 2.0 to 3.1 nanometers in diameter as the layers were added. The ZnInS2 layer played a critical role: it passivated sulfur vacancies and shallow trap states that would otherwise capture electrons and waste energy as heat rather than light.
Time-resolved photoluminescence measurements showed that the radiative recombination component increased from 73.6% to 85.7% after the introduction of the interfacial layer, while the non-radiative component dropped by nearly half. Temperature-dependent photoluminescence revealed a thermal activation energy of 65.7 millielectronvolts for the layered quantum dots - more than 2.5 times that of the control sample without the interfacial layer - indicating that non-radiative recombination was substantially suppressed.
Density functional theory calculations further visualized the effect: quantum dots without the interfacial layer showed distinct surface trap states with uneven charge distribution, whereas those with the ZnInS2 layer exhibited a homogeneous alternation of charge-gain and charge-loss regions, confirming effective defect passivation. The optimized quantum dots achieved a photoluminescence quantum yield of 95.3% at 632 nanometers with a full width at half maximum of just 78 nanometers - among the narrowest ever reported for copper chalcogenide quantum dots in the red region.
"The key insight was that we needed to do more than just grow a protective shell around the quantum dots," the authors said. "By inserting a specifically designed interfacial layer, we were able to neutralize the defects that were introducing additional recombination pathways and broadening the emission spectrum. This gives us a clear path to using these non-toxic materials in applications where color purity really matters - without sacrificing the brightness that makes quantum dots so attractive in the first place."
The team fabricated proof-of-concept red quantum dot light-emitting diodes using the optimized materials. The devices achieved a maximum luminance of 412 candelas per square meter and an external quantum efficiency of 4.9% - roughly a threefold improvement over devices made without the interfacial layer. The operational stability also improved, with the time to 50% initial luminance increasing from 110 to 170 seconds.
Beyond displays, these quantum dots could find applications in luminescent solar concentrators, bioimaging, and other optoelectronic devices where both high efficiency and color purity are essential. The interfacial engineering approach demonstrated here offers a generalizable strategy for overcoming the defect-related limitations of other copper chalcogenide quantum dot systems, potentially accelerating the development of cost-effective, environmentally friendly optoelectronics that can compete with - and eventually replace - their toxic counterparts.