Functional nanophotonics for active optoelectronic devices

This section presents selected highlights from our research in solution-processed and bottom-up developed functional nanophotonics applied for active optoelectronic devices.

Our work aims to design devices whose response is governed by localized photonic and photothermal mechanisms, rather than by conventional carrier photogeneration in a semiconductor. Illumination induces processes such as plasmonic excitation, electromagnetic field confinement, and local heating, which modify optical absorption and the thermal state of the device and thereby shape its optoelectronic response.

This approach enables alternative optoelectronic functionalities, particularly for near-infrared and short-wave infrared (SWIR) photodetection, as well as for energy harvesting under low photon flux.

I. Hybrid photodetection and plasmonic enhancement

We developed hybrid phototransistor combining graphene, perovskites, and colloidal metallic plasmonic nanoantennas, where plasmonic enhancement locally strengthens light–matter interaction near active interfaces.

Under a phototransistor device structure (as shown in figure below), due to graphene’s atomic thickness, the near field, generated upon localized surface plasmon resonance excitation of the gold nanoparticles, efficiently penetrates into the perovskite layer at the interface boosting the carrier generation in this region where charge transfer to graphene is most effective. This leads to a significant increase in responsivity compared with the control devices without plasmonics.

Figure caption: (a) Schematic of the device structure applied; (b) The photo-switching characteristics of the perovskite-graphene (P-G) and perovskite-graphene-gold NPs (P-G-Au NPs) devices under alternating dark and illumination conditions.

Publication :

Sun, Z. ; Aigouy, L. ; Chen, Z. Plasmonic-Enhanced Perovskite–Graphene Hybrid Photodetectors. Nanoscale 2016, 8 (14), 7377–7383. https://doi.org/10.1039/C5NR08677A.

II. Photon conversion and spectral modification by upconversion nanoparticles

We explored upconversion nanoparticles (UCNPs) as functional building blocks to extend the spectral response of optoelectronic devices beyond the intrinsic absorption limit determined by the bandgap of the active absorbers.

By integrating UCNPs inside a perovskite solar cell, we demonstrated a measurable contribution to photocurrent generation under infrared excitation. Spatially resolved photocurrent mapping enabled direct identification and quantification of this contribution.

Figure caption: (a) Schematic of the architecture of a perovskite solar cell in which half of the interface is decorated with upconversion nanoparticles (UCNPs), together with the experimental setup for light-beam-induced current mapping (micro-LBIC).
(b) Photocurrent maps induced by upconversion (λ_ex = 980 nm) obtained by micro-LBIC, highlighting the contribution of the UCNPs, correlatable with their upconversion fluorescence.

In a similar spirit, we showed that incorporating UCNPs into flexible organic photodiodes enables photodetection at λ ≈ 1.5 µm, via photon upconversion and energy transfer processes between the UCNPs and the organic absorber. This provides an alternative route to infrared photodetection compatible with lightweight, flexible, and solution-processed materials.

Figure caption: (Left) Schematic of the architecture of a hybrid photodetector based on a bulk heterojunction (BHJ) (DPPTT-T/PC₇₀BM) incorporating upconversion colloidal nanoparticles (UCNPs); (Right) Temporal evolution of the photocurrent of these hybrid photodetectors under laser illumination at λ = 1.5 μm. The inset shows an image of a fabricated flexible hybrid photodetector.

It is important to note that these studies differ from the use of UCNPs as metrological probes: here, UCNPs act as a functional elements of optoelectronic conversion, illustrating their versatility for creating new device functionalities through nanoscale photonic engineering.

Publications:

⦁ Schoenauer Sebag, M. ; Hu, Z. ; de Oliveira Lima, K. ; Xiang, H. ; Gredin, P. ; Mortier, M. ; Billot, L. ; Aigouy, L. ; Chen, Z. Microscopic Evidence of Upconversion-Induced Near-Infrared Light Harvest in Hybrid Perovskite Solar Cells. ACS Appl Energy Mater 2018, 1, 3537–3543. https://doi.org/10.1021/acsaem.8b00518.
⦁ Xiang, H. ; Hu, Z. ; Billot, L. ; Aigouy, L. ; Zhang, W. ; McCulloch, I. ; Chen, Z. Heavy-Metal-Free Flexible Hybrid Polymer-Nanocrystal Photodetectors Sensitive to 1.5 Μm Wavelength. ACS Appl Mater Interfaces 2019, 11 (45), 42571–42579. https://doi.org/10.1021/acsami.9b14034.

III. SWIR photodetection by photothermal conversion

Another approach relies on the plasmonic-induced photothermal conversion for near-infrared and SWIR photodetection. In these “bolometer-inspired” devices, photons excite the localized surface plasmon resonances in plasmonic nanoparticles, whose ultrafast relaxation produces local heating, which is then transduced into an electrical signal.

Figure caption: (a) Schematic of a thermistor decorated with plasmonic colloidal gold nanorods (Au NRs); (b) Optical absorbance spectra of different batches of gold nanorods in aqueous solution, exhibiting distinct LSPR absorption peak associated with different aspect ratios; (c) Photoelectric response of the hybrid NR–thermistor device under illumination at different wavelengths in the short-wave infrared (SWIR), compared with that of the reference thermistor without nanorods (open gray symbols).

We demonstrated this concept in hybrid architectures combining plasmonic gold nanorods with sensitive elements, such as thermistors (figure above) or platinum microwires (figure below), enabling SWIR detection governed by thermal dissipation and transport rather than by semiconductor bandgap absorption. This strategy circumvents the intrinsic limitations of conventional SWIR materials (e.g. III–V semiconductors, PbS, Ge, etc.), which are often costly, toxic, or require high-temperature growth.

Figure caption: (Left) SEM image of a hybrid short-wave infrared (SWIR) photodetector combining gold nanorods and a platinum microwire; (Center) Magnified view of the platinum microwire showing dense decoration with gold nanorods on its surface; (Right) Time-dependent photoinduced response of the hybrid AuNR/Pt photodetector under laser illumination at λ = 1.5 µm.

Publications :

⦁ Xiang, H. ; Niu, T. ; Schoenauer Sebag, M. ; Hu, Z. ; Xu, X. ; Billot, L. ; Aigouy, L. ; Chen, Z. Short‐Wave Infrared Sensor by the Photothermal Effect of Colloidal Gold Nanorods. Small 2018, 14 (16), 1704013. https://doi.org/10.1002/smll.201704013.
⦁ Xiang, H. ; Hu, Z. ; Billot, L. ; Aigouy, L. ; Chen, Z. Hybrid Plasmonic Gold-Nanorod–Platinum Short-Wave Infrared Photodetectors with Fast Response. Nanoscale 2019, 11 (39), 18124–18131. https://doi.org/10.1039/C9NR04792A.

IV. Photothermoelectric conversion and energy harvesting

Building on photothermal concepts, we exploited the coupling between colloidal plasmonic nanoantennas and thermoelectric materials for energy harvesting via the photothermoelectric effect. In such devices, the plasmonic-induced photothermal effect locally boost the thermal gradient, which is then converted into an electrical voltage through the Seebeck effect.

We demonstrated hybrid photothermoelectric generators fabricated by solution processing, operating under ambient solar illumination and compatible with flexible substrates. Optimization of thermoelectric materials and nanoantenna integration led to increased output power, illustrating an alternative route for low-flux energy conversion.

Figure caption: Schematic of the architecture of the hybrid p/n PEDOT:PSS/Ag₂Se photo-thermoelectric generator activated by plasmonic nanoantennas deposited onto the hot-end. The device is designed for direct solar energy harvesting and is distinguished by its flexibility and compatibility with wearable applications.

Publications :

⦁ Xin, C. ; Hu, Z. ; Fang, Z. ; Chaudhary, M. ; Xiang, H. ; Xu, X. ; Aigouy, L. ; Chen, Z. Flexible and Wearable Plasmonic-Enabled Organic/Inorganic Hybrid Photothermoelectric Generators. Mater. Today Energy 2021, 22, 100859. https://doi.org/10.1016/j.mtener.2021.100859.
⦁ Xin, C. ; Fang, Z. ; Jiang, S. ; Hu, Z. ; Zhang, D. ; Cassagne, F. ; Aigouy, L. ; Chen, Z. Solution-Processed Flexible n-Type S-Doped Ag2Se Thermoelectric Generators for near-Ambient-Temperature Energy Harvest. Mater Today Energy 2023, 33, 101266. https://doi.org/10.1016/j.mtener.2023.101266.

V. Active devices based on phase-change materials

Finally, we coupled colloidal plasmonic nanoantennas with phase-change materials, such as vanadium dioxide (VO₂), to introduce intrinsic nonlinearity and a response dependent on the internal state of the material. We developed hybrid plasmonic/VO₂ photodetectors using fully solution-processed approaches compatible with a wide range of substrates.

This hybrid Au-nanorod/VO₂ platform combines enhanced optical absorption by nanoantennas, photothermal conversion, and electrical modulation through material phase transition. It marks a transition from plasmonically enhanced “passive” devices to truly active optoelectronic systems, whose response can be tuned by optical, thermal, or electrical stimuli.

These results open the way to advanced functionalities such as nonlinear detection, optoelectronic switching, and reconfigurable response.

Figure caption: (a) Schematic of the hybrid plasmonic Au nanorods (NR)/VO₂ photodetector with colloidal NRs coupled to a vanadium dioxide thin film; (b) Decoration with Au NRs strongly modifies the photoinduced phase transition behavior of the underlying VO₂ under laser illumination (λ_laser = 1.5 μm); (c) Photoelectric response of the hybrid device, expressed as ΔR/R, compared with that of the reference device without Au NRs, for different laser powers.

Publication:

Fang, Z. ; Zimmers, A. ; Li, K. ; Zhang, D. ; Lan, T. ; Sun, B. ; Billot, L. ; Aigouy, L. ; Chen, Z. Hybrid Plasmonic Nanorods/VO₂ Photodetectors Sensitive to Short‐Wave Infrared Photons with Fast Response. Adv Electron Mater 2025, 11 (14). https://doi.org/10.1002/aelm.202500172.