OCN research


Infrared optoelectronic using nanocrystals

The group is involved in the design of infrared optoelectronics devices using narrow band gap nanocrystals as active materials

This research topic is highly pluridisciplinar with

Nanocrystal synthesisOptoelectronic devicesElectronic structure investigationFunding


  • Nanocrystals synthesis, including the development of new growth method.

Image of nanocrystal synthetic setup

For example, we report the first highly concentrated synthesis of HgTe nanocrystals by swicthing from conventional mercury salts to liquid mercury as precursor. We thus obtained the most concentrated synthesis of HgTe nanpocrystal ever reported with concentration close to 100 g/L. This new synthetic route is promissing to achieve greener synthesis of HgTe with reduced exposure of work force to Hg precursor.

Scheme of liquid Hg based synthesis of HgTe nanocrystals

We have also been the first to report nanocrystals with THz absorption. A new synthetic procedure has enable the growth of nanocrystal with size above the Bohr radius, thus enabling absorption up to 100 µm. This work demonstrated the possibility to tune the absorption of HgTe nanocrystal all over the infrared from 1 to 100 µm

Infrared spectra of HgTe nanocrystals with various sizes


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  • Electronic transport with gate, temperature and time resolved possibilities

Device performance directly relates to their transport properties. Investigation of the transport is thus a central topic in the group. We have develloped instrument to conduct measurement with Fermi level (ie with gate) and temperature with a resolution down to sub fA. We are also equipped to conduct photoconduction measurements (from UV to mid IR) with spectral and time resolved experiments. The instruments used to measured transport are not limited to nanocrystals fo HgTe and we also explore other materials such as TMDC, germanane, and other nanomaterials.

TCO dual gate

Schematic of dual gated pn junction made from nanocrystals


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  • Design of the light matter coupling to achieve high absorption and spectral shaping

A central point in the design of infrared sensor using nanocrystal is the tradeoff between absorption and carrier transport. Absorption pushed toward thick film (1 µm and more) but this is incompatible with the short carrier diffusion length resulting from hopping transport. By integrating plasmonic resonator, such as guided mode resonator, we are able to focus the light on a thin slab of semiconductor and achieve absorption close to unity. This strategy can also be used to design on demand absorption spectral or to offer spectral tunability beyond the material quantum confinement.

Scheme of a device coupling light resonator and nanocrystal to achieve broadband infrared sensing-Picture has been selected as cover of Advanced Optical Materials.

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  • Integration of nanocrystals for the fabrication of infrared imaging system

Nanocrystals offer great promissises as low-cost alternative to epitaxially grown infrared absorpbing semiconductor. This is especially true in the short wave infrared, where the cost of current sensor remains uncompatible with many new infrared applications such as industrial vision. In collaboration with New Imaging Technologies, we design short wave infrared focal plane array where nanocrystal are used to functionalize a CMOS read out circuit to obtain short wave infrared photoconduction.


A video highlighting the transformation of nanocrystal solution into infrared camera


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  • Infrared light emission

The group also works on light emission in geometrical LED geometry using nanocrystals as light emitter. Our interest goes beyond just the LED performance and we integrate LED for active imaging. In the infrared, the reflexion constrast can be quite different from the visible and this can be used for moisture detection for example, see the figure below.


toc LED 2um

 Left scheme of an infrared LED based on HgTe Nanocrystals.


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Devices integration necessarily requires a deep knowledge on the material electronic structure. Our main builiding block is HgTe nanocrystal which combine bulk inverted band structure with quantum confinement and surface chemistry dependence. It is thus of utmost importance to unveil band alignment of this material in absolute energy scale to be able to efficiently integrate it into devices with the right band alignment (low Schottky barrier). To reach this goal, we use a combination of infrared spectroscopy and photoemission (conducted on tempo and Antares beamline of synchrotron Soleil). We also use time-resoved photoemission which is a precious tool to probe carrier relaxation dynamics as well as surface band bending.

Tempo beamline

Photo of tempo beamline at Soleil

We also use intensively infrared spectroscopy including under pressure at Smis Beamline of Soleil.


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Our research activities is funded by

French DOD through project NITQuantum

ERC through starting grant (BlackQD – 2018-2024) and consolidator grant (AQDtive – 2024-2029))


Agence nationale de la recherche through project Copin, Frontal, Graskop, Bright, MixDFerro, Quicktera

Past funding by Nexdot, ANR (Iper-Nano2)


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