Infrared Doped Colloidal Nanocrystals – FRONTAL
Boosted by environmental concerns in our thermo-industrial civilization and massive integration, new infrared applications like mobile pollution monitoring or thermal imaging for building energy management are emerging. These applications concern widely medical and military and industrial fields, along with every day civil life. The core of these applications requests light detectors in the blackbody infrared spectral range (wavelength larger than 3 µm) that are low cost. Current technologies based on epitaxially grown semiconductors or organic electronics or microbolometers are unlikely to bring simultaneously a cost disruption with high performances. In contrast colloidal quantum dots (CQDs) are simple and cost-effective chemically synthesized, and very recently has been shown to exhibit self-doping and natural size tunable strong mid and far infrared features.
However fundamental theoretical and experimental background data are critically missing for their use and optimization in infrared devices and more generally as active center for (nano)photonics and emerging colloidal infrared optoelectronics. At present the intrinsic dynamics of n-doped CQDs, on which depends the performances of devices, is essentially unknown. The mechanisms of the energy relaxation of a confined electron, or several of them, is yet to be identified. The optical and electronic response down to the single quantum dot level has never been measured. The importance of the electron-phonon coupling still need to be ascertained.
The fundamental FRONTAL project specifically addresses this missing knowledge. FRONTAL will quantify and analyze the optical response and ultrafast dynamics of doped CQD in the near, mid and far infrared region (1-20 µm wavelengths). For their proximity with the HgCdTe material used in industrial infrared detection, self-doped HgSe and HgTe nanocrystals will serve as a common material. A green Ag2Se alternative will also be considered. Based on a combination of cutting-edge techniques exploiting the electronical, optical, acoustical, thermal signatures of these nanostructures, and 3D modeling in k.p multiband formalism, the 6 partners will:
1. Give a detailed theoretical and experimental picture of the optical response self-doped CQDs in the whole infrared spectral range going down to the challenging nanometric scale and single particle level.
2. Measure the times and identify the mechanisms ruling the relaxation of energy over the range 30 fs – 10 µs using ultrafast pump-probe spectroscopy in resonance with the mid and far infrared intraband transitions and time-resolved photo-emission.
3. Study electron-phonon coupling as a key intrinsic interaction thanks to measurement of the ultrafast photoacoustic response, as well as pump-probe spectroscopy using infrared and electronic diffraction probes.
4. Discuss the potential of doped colloidal nanocrystals for infrared optoelectronics in relation to an industrial French leader of infrared detection.
Beyond scientific and academic impact, FRONTAL will bring colloidal self-doped nanocrystals closer to the infrared market. Based on several different signatures of optical, electronic, acoustical and thermal origins, the project will provide spectral, nanometric spatial, and ultrafast time resolved data to envision of the next generation of low-cost infrared devices and help a more realistic design and optimization of doped CQD based infrared technologies that are presently emerging.
Monsieur Sébastien Sauvage (Centre de Nanosciences et de Nanotechnologies)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
LOA Laboratoire d'Optique Appliquée
INSP Institut des nanosciences de Paris
CNRS C2N-STM Centre de Nanosciences et de Nanotechnologies
UPSud C2N-QD Centre de Nanosciences et de Nanotechnologies
SOLEIL SYNCHROTRON SOLEIL
Help of the ANR 601,475 euros
Beginning and duration of the scientific project: December 2019 - 48 Months