The integration of luminescent nanomaterials into scalable semiconductor platforms is vital for the future of on-chip photonics. Carbon dots (CDs) have emerged as a promising low-dimensional material platform, offering significant advantages over conventional luminescent materials, including enhanced photostability, lower toxicity, and scalable synthesis. However, implementing CDs in solid-state configurations and thin films remains a challenge. When transferred to a dry form, CDs often suffer from aggregation, leading to pronounced photoluminescence quenching, a drastic reduction in quantum yield, and reduced optical efficiency, which hinders their direct implementation in photonic devices.
In a new paper published in Light: Advanced Manufacturing, a team of scientists, led by PhD. Valeriy M. Kondratev and Dr. Alexey D. Bolshakov from Alferov University and the Moscow Center for Advanced Studies, along with co-workers from ITMO University and St. Petersburg State University, have demonstrated a novel approach to overcome these limitations. They successfully fabricated robust fluorescent nanostructures by hybridising solution-processed CDs with single-crystalline semiconductor nanowires (NWs) grown directly on silicon (Si) substrates.
Based on this hybrid architecture, the team systematically investigated the photoluminescence of CDs deposited on gallium nitride (GaN), gallium phosphide (GaP), and silicon (Si) NW hosts. They discovered that the intrinsic electronic and optical properties of the host NWs rigorously govern the emission characteristics of the integrated CDs. Most importantly, they demonstrated that the absorption edge of the host nanowire acts as a definitive and practical spectral filter.
Efficient excitation of the CD photoluminescence occurs exclusively for photon energies below this absorption edge, whereas higher-energy photons are parasitically absorbed by the host material. As a result, the emission spectrum can be precisely tailored through rational host selection. For example, the wide direct bandgap of GaN allows for the broadest excitation window in the visible range, while GaP NWs restrict high-efficiency photoluminescence to the green-red spectrum, and Si NWs highlight the tradeoff between CMOS compatibility and high visible-range absorption losses.
The scientists summarize the operational advantages of their platform: "Beyond spectral filtering, the NW morphology actively enhances performance through optical confinement and waveguiding, which is particularly evident in GaP structures". The high aspect ratios and large specific surface areas of the NWs provide a high density of surface sites for emitter adsorption, acting as efficient waveguides that enable strong light coupling and enhanced interactions with the luminescent centers.
By coupling the tuneable chemistry of CDs with the tailored optoelectronics of semiconductor NWs, this study establishes a scalable host–guest architecture for engineering nanoscale light sources.
"This approach offers a powerful and flexible platform for the development of integrated nanophotonic light sources for sensing, on-chip communication, and quantum technologies," the scientists forecast.
Light: Advanced Manufacturing
Host-engineered carbon dot luminescence: integration with nanowires for photonics