Efficient short-wave infrared emission by copper-doped InP/ZnSe/ZnS quantum dots for high-performance luminescent solar concentrators
image: InP-based quantum dots (QDs) are summarized with their photoluminescence quantum yields and emission wavelengths. The star marker indicates the performance of our synthesized QDs, which show spectral matching with the responsivity of silicon solar cells and achieve a PLQY of 66% at 960 nm. Our liquid luminescent solar concentrator (LSC) incorporates copper-doped InP core QDs with a lattice-matched ZnSe/ZnS multishell structure.
Credit: Nano Research, Tsinghua University Press
The short-wave infrared (SWIR) region (0.9–2.0 µm) of the solar spectrum holds great promise for applications ranging from medical imaging to next-generation solar energy collectors. However, developing efficient, non-toxic materials that emit light in this range has been a significant challenge.
A research team from Koç University called IDEALAB (Innovative DEvices and interfAces LABoratory (IDEALAB) has now synthesized copper-doped indium phosphide quantum dots (Cu:InP QDs) that achieve a record-high photoluminescence quantum yield (PLQY) of 66% with an emission peak at 960 nm, setting a new benchmark for performance in the SWIR window.
This breakthrough paves the way for high-performance, eco-friendly infrared optoelectronic devices. The team published their findings in the prestigious journal Nano Research.
"To harness the potential of InP QDs for applications requiring emission in the SWIR, we had to overcome the long-standing issue of low efficiency in this spectral range," said Professor Sedat Nizamoglu, corresponding author of the paper and the chair of the Electrical and Electronics Engineering Department at Koç University. " In this study, we demonstrate a synthesis strategy for efficient SWIR-emitting InP quantum dots via sensitive control of the core nucleation, copper doping and shell growth."
Quantum dots are nanoscale semiconductors with unique light-emitting properties. While InP-based QDs are game-changing and non-toxic nanomaterials for display technology, they exhibited low PLQY in the SWIR region, limiting their use in applications like bioimaging, biosensors, and luminescent solar concentrators (LSCs).
The team's innovation lies in a refined synthesis process. They used a low-cost, safe phosphorus precursor and omitted the zinc halide source (ZnCl2), which typically limits particle size and restricts emission to shorter wavelengths. Introducing copper atoms into the InP core creates midgap states that allow for a large Stokes shift, effectively tuning the emission into the infrared range. Subsequently, the epitaxial growth of a lattice-matched ZnSe/ZnS multishell onto the core further suppressed nonradiative recombination, resulting in highly efficient red-to-SWIR Cu-doped InP QDs.
To demonstrate practical utility, the team integrated the QDs into an LSC. The researchers designed a structural configuration using a solid-state PDMS polymer as a light-guiding layer to form a cavity that houses the QD solution, serving as the luminescent interlayer. This liquid QD integration preserves PLQY and spectral properties. The structure efficiently trapped the emitted light, leading to a high optical efficiency of 7.36%.
"This performance arises from the synergistic combination of the QDs' high quantum yield, their spectral alignment with the peak responsivity of silicon solar cells (900-1000 nm), and our optimized waveguide design," explained Tarik Safa Kaya, first author of the study from the Department of Materials Science and Engineering at Koç University. "It highlights the great potential of these nanomaterials to serve as the active component in sustainable energy harvesting technologies."
The team anticipates that their high-performance, cadmium-free quantum dots will not only advance LSC technology but also open new avenues in other SWIR applications.
"These findings underscore the promise of InP QDs beyond visible spectrum," said Professor Nizamoglu. "We believe this work is an inspiring step forward for high-performance InP based infrared optoelectronics."
Other contributors include Ugur Berkay Caliskan, Parsa Kaviani, Asim Onal, Eren Tekinay, Guncem Ozgun Eren, Hande Gunduz, Hadi Jahangiri, and Ugur Unal from Koç University, along with Mehmet Silme and Kadriye Kutlay from Berteks Tekstil Sanayi ve Ticaret A.Ş.
This work was supported by Berteks Tekstil Sanayi ve Ticaret A.Ş.
About Nano Research
Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 7,000 articles. In 2024 InCites Journal Citation Reports, its 2024 IF is 9.0 (8.7, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.