About

Philippe Guyot-Sionnest is a professor at the University of Chicago, appointed jointly in the departments of physics and chemistry. He works on laser spectroscopy and colloidal nanoparticles. His research focuses on the tremendous potential at the nanoscale where chemistry excels and physics predicts that many properties can be tuned. His work involves investigating quantum states, charging, spin, phonons, and plasmons at the nanometer scale, utilizing colloidal synthesis to chemically precipitate nanostructures. His research group is driven by physical concepts and enabled by synthesis, contributing to advancements such as better methods for infrared light production using quantum dots and breakthroughs in infrared camera technology.

Selected publications

• Midinfrared Electroluminescence from CdSe Quantum Dots

  ACS Nano · 2025-02-02 · 10 citations

  articleSenior authorCorresponding

  Midinfrared electroluminescence from the electron intraband transition is demonstrated with intrinsic CdSe colloidal quantum dots. The device consists of a thin film of CdSe dots and a layer of ZnO nanocrystals, sandwiched between two electrodes that enhance light outcoupling at 5 μm. At 100 mA and 15 V, the electron-to-photon efficiency is 0.40%, and the power conversion efficiency is 0.013%. The devices show good air and thermal stability. Electron transport layers and surface traps are discussed.

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• <i>(Keynote)</i> Electrochemical Studies of Infrared Colloidal Quantum Dots, Towards Detectors and LEDs

  ECS Meeting Abstracts · 2025-11-24

  article1st authorCorresponding

  Colloidal quantum dots (CQD) are unique soluble infrared chromophores. As with polymers two decades earlier, electrochemical studies were the first to establish a basic understanding of carrier doping in CQDs, and to demonstrate methods to facilitate charge transfer in films of dots. This led to early proof of principle of CQD near-infrared photodetectors. CQD detectors have now been demonstrated in the short-wave infrared (&lt; 2microns), mid-infrared (&lt;5 microns), and long-wave infrared (&lt;12 microns), in order of increasing difficulty and reduced performance. One striking milestone was the detection of thermal radiation with background limited sensitivity. This has led to the realization of thermal imaging sensors with simple spin-on colloidal dots on CMOS chips. CQD films can also be used for electrically driven infrared sources and a recent milestone was the observation of cascade mid-infrared emission under high bias. Performances are still below those of epitaxial HgCdTe or quantum well technologies, but they are not yet fundamentally limited. It seems that research on varying the starting semiconductor materials, improving the size control, characterizing the doping properties, regulating the charge transfer properties, and increasing the emission efficiency, will lead to competitive or superior performances. Increasing emission efficiency is the one with the greatest payoff. Since fast and sensitive infrared detectors, diode arrays, and imagers, are beyond consumer's budgets and in limited supply, a broad effort in infrared CQDs could transform access to IR technologies for chemical sensing, machine vision, and transportation.

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• Guidelines for accurate evaluation of photodetectors based on emerging semiconductor technologies

  Nature Photonics · 2025-11-01 · 47 citations

  articleOpen access
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• Characterization of Mid-Infrared HgTe Colloidal Quantum Dot Photodiodes

  ACS Applied Materials & Interfaces · 2025-02-27 · 2 citations

  articleSenior authorCorresponding

  Top-illuminated mid-infrared HgTe colloidal quantum dot (CQD) photodiodes are compared with back-illuminated photodiodes. For top- and back-illuminated diodes, respectively, at 290 K, the external quantum efficiencies are 10% and 21%, the detectivities are 5.1 × 108 and 9.4 × 108 jones, and the cutoffs are 3.9 and 3.8 μm. The efficiencies peak around 110 K at 38% and 67%, respectively. The diodes are background limited below 130 and 140 K, respectively. Above 140 K, the IV curves fit well with a single diode model with a unity ideality factor, indicating the dominance of geminate recombination. The reduced activation energy of the dark current compared to the cutoff energy is explained by the finite edge width. Below 140 K, the ideality factor increases, indicating the growing importance of trap-like recombination. A photoconductive shunt resistance limits performance at low temperatures, which is proposed to originate from the hopping transport in CQDs, rather than device defects.

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• Shape-Controlled HgTe Quantum Dots for Room-Temperature Mid-Infrared Photoconductors

  ACS Photonics · 2025-11-07 · 4 citations

  articleSenior authorCorresponding

  HgTe quantum dots are synthesized as relatively monodispersed nanoparticles with spherical, partially spherical, and tetrahedral shapes. The colloidal stability is in the order spherical ≈ partially spherical > tetrahedral, and the first exciton strength is in the order tetrahedral ≈ partially spherical > spherical. Intrinsic films are made using nonpolar and polar ligand exchange and treated with a mild etching solution of HgCl2. They are tested as mid-IR photoconductors with a 4 μm cutoff. For all films, the carrier lifetime is geminate recombination-limited between 250 and 330 K. Partially spherical dots emerge with the longer carrier lifetime and higher signal-to-noise ratio. 200 nm thick films deposited on an optical resonant grating architecture with a 1.5 μm channel gap achieve a saturated external quantum efficiency of 65% at 2 V bias, for light polarized across the gap, with a room temperature detectivity of 0.8 × 1010 Jones at 2450 cm–1, 10 kHz and 0.27 V bias, and response time of about 200 ns. This is the highest room temperature detectivity achieved for HgTe dots at 2450 cm–1 and below.

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• Relatively Bright Intraband 5 μm Photoluminescence from HgSe/CdS Quantum Dot Films after Lead Halide Treatment

  The Journal of Physical Chemistry Letters · 2025-06-06

  articleSenior authorCorresponding

  The 5 μm intraband photoluminescence (PL) from 200 nm thin films of n-doped mercury selenide/cadmium sulfide (HgSe/CdS) core/shell colloidal quantum dots reaches 0.2% apparent external efficiency, after solid-state ligand exchange with a solution of lead iodide (PbI2) and annealing at 140 °C. The PbI2 treatment removes 95% of the C–H vibration absorption, but the PL increase is correlated with improved n-doping and not with organic ligand removal. The integrated emission intensity increases only by 20% upon cooling from 423 to 85 K. This suggests that multiphonon relaxation is not limiting the PL and that brighter emission should still be possible. PbI2 treatment gave the brightest films, but PbBr2 and PbCl2 have similar effects.

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• Long-Wave Infrared HgTe Quantum Dot Photoconductors with Optical Enhancement

  ACS Nano · 2025-04-28 · 10 citations

  articleSenior authorCorresponding

  HgTe quantum dots are studied for long-wave infrared detection using interband absorption. The optical constant, photoluminescence, mobility, carrier lifetime, and doping are measured. Simple photoconductors are made as films on interdigitated electrodes, and the best performance is obtained with intrinsic films of quasi-spherical HgTe particles that have been cast from polar inks and exposed to HgCl2 solutions. As the temperature is lowered to 85 K, the photoresponse extends past 8 μm. The performance is limited by a low absorption coefficient near the absorption edge and by a very short exciton lifetime as determined by the photoluminescence quantum yield of 10–5. A metal–insulator–metal structure combined with gold nanoantennas and a 100 nm thick HgTe dot film gives a ∼20-fold increase in responsivity and detectivity for a peak resonance at 8.5 μm at 85 K. The best detectivity is 1.47 × 1010 Jones at 0.8 V bias, 25 kHz frequency, and TE polarization. An external quantum efficiency (EQE) of 12.5% is also achieved at a higher bias.

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• Intraband cascade electroluminescence with weakly n-doped HgTe colloidal quantum dots

  The Journal of Chemical Physics · 2024-09-24 · 3 citations

  articleSenior author

  Room temperature 6 μm intraband cascade electroluminescence (EL) is demonstrated with lightly n-doped HgTe colloidal quantum dots of ∼8 nm diameter deposited on interdigitated electrodes in a metal-insulator-metal device. With quantum dot films of ∼150 nm thickness made by solid-state-ligand-exchange, the devices emit at 1600 cm-1 (6.25 μm), with a spectral width of 200 cm-1, determined by the overlap of the 1Se-1Pe intraband transition of the quantum dots and the substrate photonic resonance. At the maximum current used of 20 mA, the bias was 30 V, the external quantum efficiency was 2.7%, and the power conversion efficiency was 0.025%. Adding gold nano-antennas between the electrodes broadened the emission and increased the quantum efficiency to 4.4% and the power efficiency to 0.036%. For these films, the doping was about 0.1 electron/dot, the electron mobility was 0.02 cm2 V-1 s-1, and the maximum current density was 0.04 kA cm-2. Higher mobility films made by solution ligand exchange show a 20-fold increase in current density and a 10-fold decrease in EL efficiencies. Electroluminescence with weak doping is interesting for eventually achieving electrically driven stimulated emission, and the requirements for population inversion and lasing are discussed.

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• Mid-infrared intraband electroluminescence on planar interdigitated electrodes

  Matter · 2024-03-11 · 7 citations

  articleSenior authorCorresponding
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• High Mobility HgTe Quantum Dot Films with Small Energy and Dynamic Disorder

  The Journal of Physical Chemistry C · 2024-04-15 · 6 citations

  articleSenior authorCorresponding

  The transport properties of HgTe colloidal quantum dot films are studied from 4 to 300 K with larger and more monodispersed quantum dots than previously. With nanocrystals of 14 nm diameter and 6.5% size distribution, a peak mobility of 65 cm2/(V s) is measured at 65 K for state-resolved transport in the 1Se state. Above 70 K, the mobility is band-like, but it follows the Marcus electron hopping model, while being far below the Mott–Ioffe–Regel limit. At 65 K, the average hopping time is as fast as 1 ps and getting close to the estimated dephasing time, or dynamic disorder, of the 1Se state, suggesting that coherence may exist for some neighboring dots. At lower temperatures, the mobility decreases for low bias, but it is temperature-independent for high bias due to field-driven transport. The Efros–Shklovskii variable range hopping model gives localization lengths of ∼100 nm, also suggesting large coherent domains. Twice lower mobility and shorter localization lengths are obtained with a 10 μm channel compared to a 2 μm channel, suggesting a possible percolation of the more conducting domains.

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Awards & honors

• Fellow of the American Physical Society