CIGS-ZIS-ZnS quantum dots reach 95.3% PLQY at 632 nm; red QLED prototype shows ~5% EQE

A team led by the University of Electronic Science and Technology of China, with Panzhihua University, the Chinese Academy of Sciences and other institutions, has developed eco-friendly CuInGaS-ZnInS-ZnS (CIGS-ZIS-ZnS) quantum dots for red light-emitting diodes. The work was published in September 2026 in eScience (Volume 6, Issue 5, Article 100536). The dots reached a photoluminescence quantum yield (PLQY) of 95.3% at 632 nm with a full width at half maximum (FWHM) of 78 nm sciencedirect.comeSciencesciencedirect.comOpen source ↗.

The authors note that copper chalcogenide quantum dots are low-toxicity and strongly absorbing, but their copper-related vacancies and defects create several emission pathways. This broadens the emission and limits efficiency and color purity in displays.

Interfacial layer and defect passivation

The team placed a ZnInS2 interfacial layer between the CuInGaS core and the outer ZnS shell. Transmission electron microscopy confirmed growth of each layer, with the dot diameter increasing from 2.0 to 3.1 nm.

According to the authors, the ZnInS2 layer passivates sulfur vacancies and shallow trap states that otherwise capture electrons and dissipate energy as heat. Time-resolved photoluminescence showed the radiative recombination component rising from 73.6% to 85.7%, while the non-radiative component fell by nearly half. Temperature-dependent measurements gave a thermal activation energy of 65.7 meV, more than 2.5 times that of the control sample without the layer sciencedirect.comeSciencesciencedirect.comOpen source ↗.

Density functional theory calculations showed distinct surface trap states with uneven charge distribution in dots without the layer. With the ZnInS2 layer, charge-gain and charge-loss regions alternated homogeneously, consistent with defect passivation.

Red QLED prototype

As a proof of concept, the team fabricated red quantum dot light-emitting diodes (QLEDs). The devices reached a maximum luminance of 412 cd/m2 and a maximum external quantum efficiency (EQE) of 4.9%, roughly three times that of devices without the interfacial layer. The control CIGS-ZnS device gave 1.1%.

Operational stability also improved: the time to 50% of initial luminance increased from 110 to 170 seconds sciencedirect.comeSciencesciencedirect.comOpen source ↗.

The authors report that the 78 nm FWHM is among the narrowest reported for copper chalcogenide quantum dots in the red region, and that the EQE exceeds most copper chalcogenide QLEDs. They also suggest the approach could apply to luminescent solar concentrators and bioimaging.