Photothermoelectric Effect Research Articles

Intrinsically anisotropic 1D NbTe4 for self-powered polarization-sensitive photodetection

Polarization-sensitive photodetection enhances scene information capture, crucial for modern optoelectronic devices. One-dimensional (1D) materials with intrinsic anisotropy, capable of directly sensing polarized light, are promising for such photodetectors. NbTe4, a quasi-1D transition metal tetra-chalcogenide, offers significant benefits for polarization-sensitive photodetection due to its structural anisotropy. Nonetheless, to date, the anisotropic properties of 1D NbTe4 have not been reported. Herein, NbTe4 nanobelts were synthesized via mechanical exfoliation from needle-like bulk crystals, and their anisotropic and optoelectronic properties were comprehensively studied. Angle-resolved polarized Raman spectroscopy, in conjunction with azimuth-dependent reflectance difference microscopy, confirmed that 1D NbTe₄ exhibits intrinsic structural and in-plane optical anisotropy. The 1D NbTe4 device demonstrated characteristic anisotropic photodetection behavior, achieving dichroic ratios of 1.16 at 671 nm and 1.25 at 1064 nm. Meanwhile, the device exhibits a pronounced photothermoelectric effect, conferring a broad spectral photoresponse ranging from visible to near-infrared wavelengths (532-1064 nm), with a rapid response time of 158 ms. This study demonstrates that NbTe4 inherently possesses in-plane anisotropy, making it a promising candidate for polarization-sensitive photodetection applications.

N-Type Nanocomposite Films Combining SWCNTs, Bi2Te3 Nanoplates, and Cationic Surfactant for Pn-Junction Thermoelectric Generators with Self-Generated Temperature Gradient Under Uniform Sunlight Irradiation.

Flexible thermoelectric generators (TEGs) with pn-junction single-walled carbon nanotube (SWCNT) films on a polyimide substrate have attracted considerable attention for energy harvesting. This is because they generate electricity through the photo-thermoelectric effect by self-generated temperature gradient under uniform sunlight irradiation. To increase the performance and durability of the pn-junction TEGs, n-type films need to be improved as a priority. In this study, bismuth telluride (Bi2Te3) nanoplates synthesized by the solvothermal method were added to the n-type SWCNT films, including a cationic surfactant to form the nanocomposite films because Bi2Te3 has high n-type thermoelectric properties and high durability. The performances of the pn-junction TEGs were investigated by varying the heat treatment times. When the artificial sunlight was uniformly irradiated to the pn-junction TEGs, a stable output voltage of 0.47 mV was observed in the TEG with nanocomposite films heat-treated at 1 h. The output voltage decreased with increasing heat treatment time due to the decrease in the p-type region. The output voltage of TEG at 1 h is higher than that of the TEGs without Bi2Te3 nanoplates under the same conditions. Therefore, the addition of Bi2Te3 nanoplates was found to improve the performance of the pn-junction TEGs. These findings may aid in the development of facile and flexible optical devices, including photodetectors and hybrid devices integrating solar cells.

Large tunneling photo-thermoelectric voltage using cyclotron resonance in bilayer graphene/MoS2/monolayer graphene van der Waals tunnel junction

A tunnel junction using graphene in quantum Hall states (QHS) recently demonstrated the tunneling photo-thermoelectric effect (TPTE), generating a photovoltage under mid-infrared irradiation. Here, we investigate TPTE in a bilayer graphene (BLG)/6-layer MoS2/monolayer graphene (MLG) tunnel junction. The MoS2 layer facilitated the tuning of the resistance-area product RA of the tunnel junction with the gate voltage, which was challenging with the previously used h-BN barrier. The photovoltage responsivity R v due to TPTE increased with increasing RA, and achieved a maximum responsivity R v of 2.5 × 106 V W−1 at T = 2 K, which was substantially higher than earlier reports. In a device exhibiting high R v and RA, TPTE voltage was generated when the MLG was in the QHS, in contrast to the low R v and RA device, where TPTE voltage appeared at the boundary between the QHS and non-QHS. These findings provide insights into the TPTE effect for exploring the mid-infrared properties of 2D materials.

High responsivity zero-biased Mid-IR graphene photodetector based on chalcogenide glass waveguide

Graphene’s unique properties have made it a promising material for high-performance photodetectors due to its interesting features including broadband absorption, fast speed, and strong photothermoelectric effect. Here, an optimized waveguide photodetector incorporating double graphene layers with two cores is presented to boost the responsivity (∼twice), at Mid-IR range. The proposed structure operates in the zero-bias regime to eliminate the dark current issue associated with the zero bandgap nature of graphene and leads to lower noise equivalent power. The presented photodetector operating based on split gates to electrostatically induce the p-n junction in graphene channels, operates based on the photothermoelectric effect and provides responsivity, NEP, and 3 dB bandwidth of 6.3 V/W, 0.34 nW/Hz1/2, and 1.54 GHz, respectively for the detection at λ = 5.2 μm. The feasibility of the proposed structure is proved according to recent experimentally demonstrated photodetectors. Hence, the obtained results are reliable, in practice. The study has been accomplished by numerical simulation of mode profiles and solving the heat equation to extract the characteristics of the proposed photodetector. The zero-power consumption and tunability of the proposed structure make it a promising candidate for sensing, industrial, defense, and environmental monitoring applications with high accuracy.

Anomalous photo-thermoelectric effects of platinum and tungsten trioxide bilayers

We attempted to deposit a platinum (Pt) layer onto a tungsten trioxide (WO3) thin film (Pt/WO3). The Pt layer deposited on WO3 was oxidized by calcining Pt/WO3 in air to form PtOx/WO3. An n-type anomalous photo-thermoelectric (photo-TE) effect was confirmed for Pt/WO3 and Pt/HyWO3−x. HyWO3−x is a protonated WO3 after the gaschromic (GC) reaction of WO3 in Pt/WO3. The anomalous photo-TE effect was that both the electrical conductivity (σphoto) and the absolute value of the Seebeck coefficient (Sphoto) increased under UV light or visible light irradiation. After stopping the irradiation, σphoto and Sphoto decreased. In contrast, an n-type normal photo-TE effect was observed for PtOx/HyWO3−x after the GC reaction of PtOx/WO3, in which σphoto increased and the absolute value of Sphoto decreased under ultraviolet (UV) light irradiation, and vice versa after stopping the irradiation. These findings indicate that Pt was responsible for the anomalous photo-TE effect due to the electron accumulation capability of Pt, to which electrons were transferred from the conduction band of HyWO3−x. In contrast, electrons could not energetically transfer from HyWO3−x to PtO2, which existed in PtOx particles at the surface. Therefore, PtOx/HyWO3−x behaved similar to sole HyWO3−x, indicating the normal photo-TE effect.

Controlling photothermoelectric directional photocurrents in graphene with over 400 GHz bandwidth

Photodetection in the near- and mid-infrared spectrum requires a suitable absorbing material able to meet the respective targets while ideally being cost-effective. Graphene, with its extraordinary optoelectronic properties, could provide a material basis simultaneously serving both regimes. The zero-band gap offers almost wavelength independent absorption which lead to photodetectors operating in the infrared spectrum. However, to keep noise low, a detection mechanism with fast and zero bias operation would be needed. Here, we show a self-powered graphene photodetector with a > 400 GHz frequency response. The device combines a metamaterial perfect absorber architecture with graphene, where asymmetric resonators induce photothermoelectric directional photocurrents within the graphene channel. A quasi-instantaneous response linked to the photothermoelectric effect is found. Typical drift/diffusion times optimization are not needed for a high-speed response. Our results demonstrate that these photothermoelectric directional photocurrents have the potential to outperform the bandwidth of many other graphene photodetectors and most conventional technologies.

Ultra-low dark current self-powered metal-graphene-metal photodetector based on photo-thermoelectric (PTE) effect

Ultra-low dark current self-powered metal-graphene-metal photodetector based on photo-thermoelectric (PTE) effect

Recent Progress of Self-Powered Optoelectronic Devices Based on 2D Materials

Harvesting energy through light radiation is an attractive solution for powering wireless devices in the future. In particular, self-driven optoelectronic devices are especially attractive for low-energy devices on the Internet of Things. Two-dimensional (2D) materials at atomic scale thicknesses are very attractive for future self-powered optoelectronic devices due to not only their unique electronic and optical properties, but also the feasibility to fabricate desirable heterostructures, which differ from their bulk counterparts and conventional optoelectronic materials. In this review, we mainly summarized the mechanism and performance of self-powered optoelectronic devices based on 2D materials. The figure of merit and mechanism of self-driving optoelectronic devices including the interface-junction effect, bulk photovoltaic effect, and photothermoelectric effect are discussed in detail. In addition, the recent progress on the performance of self-powered optoelectronic devices based on 2D materials is compared, followed by the perspective of this field. This review is aimed to give a generalized knowledge of 2D self-powered optoelectronic devices, and thus prompt the exploration and development of novel functional devices based on 2D materials.

Key parameters to optimize the photothermoelectric effect of thermoelectric materials

Recently, photothermoelectric effect of thermoelectric materials has been hotly explored to develop self-powered and large bandwidth photodetectors working at ambient conditions. However, the key parameters for optimized photothermoelectric effect are still elusive. Here, based on the two-temperature model under static condition, we theoretically studied the key parameters to optimize the photothermoelectric performance of thermoelectric materials. Results verify that when the incident electromagnetic wave only generates electronic intra-band excitation, there is an ideal carrier concentration to optimize the photothermoelectric voltage; when the wavelength of a detected electromagnetic wave can resonantly excite quasi-particle (like phonons) except electrons, the photothermoelectric voltage can be enhanced significantly around the resonant wavelength regime; and when the electronic inter-band transition can be excited by an electromagnetic wave, photothermoelectric voltage is significantly increased due to the high optical absorption. As an example, the theoretical dependence of the photothermoelectric voltage of SnSe on wavelength is in line with the experimental result. This work elucidates the crucial parameters of thermoelectric materials to achieve the ideal photothermoelectric performance.

Enhanced optical responsivity in photothermoelectric effect of SnSe–SnSe2 composite at near-infrared band

We experimentally demonstrated that composites, being effective in optimizing the thermoelectric performance, can also enhance photothermoelectric effects in this work. In detail, we employed an alternating-growth in chemical-vapor-transport to grow the SnSe–SnSe2 composite crystals. The photo-responsivities of SnSe–SnSe2 (atomic-weight-ratio as 44%–56%) composite are comparable to SnSe crystals in the visible band (444 and 532 nm). However, the responsivities of SnSe–SnSe2 have remarkable 27.3% enhancement than those of SnSe crystal at the near-infrared band (1310 and 1550 nm). Supported by optical spectroscopy and theoretical electronic band structure, the enhanced optical responsivity of SnSe–SnSe2 composites is due to the formation of P–N junctions at interfaces between SnSe and SnSe2, leading to more optical transition channels and corresponding optical absorptions in near-infrared band. Our work verifies that hetero-junction formed among constituent compounds in composites is effective in optimizing the photothermoelectric response of thermoelectric materials in certain electromagnetic bands, paving the way to develop photoelectric detection devices.

Enhancement of the photothermoelectric effect through synergistic modulation of multiple parameters

The performance of photothermoelectric materials is severely limited by various intrinsic parameters that are difficult to simultaneously modulate, thereby hindering their applications in the fields of photodetectors, solar cells, thermoelectric therapy and so on. In this study, we have prepared suspended films composed of carbon nanotube (CNT) and molybdenum disulfide quantum dots (MoS2 QDs), which demonstrate a remarkable maximum photothermal conversion efficiency of 2201 K·mm2·W−1. This outstanding performance is attributed to the formation of a heterojunction between CNT and MoS2 QDs. Furthermore, the light absorption, temperature coefficient of resistance, and Seebeck coefficient of this suspended film are simultaneously modulated in a direction conducive to enhancing the photothermoelectric effect. Consequently, we have fabricated CNT-CNT/MoS2 QDs p-n junction photodetectors to showcase the improved photoresponse performance. This study presents an innovative approach for modulating multiple intrinsic parameters of photothermoelectric materials, which offers valuable insights for enhancing the performance of corresponding photothermoelectric devices.

Enhanced photothermoelectric conversion in self-rolled tellurium photodetector with geometry-induced energy localization

Photodetection has attracted significant attention for information transmission. While the implementation relies primarily on the photonic detectors, they are predominantly constrained by the intrinsic bandgap of active materials. On the other hand, photothermoelectric (PTE) detectors have garnered substantial research interest for their promising capabilities in broadband detection, owing to the self-driven photovoltages induced by the temperature differences. To get higher performances, it is crucial to localize light and heat energies for efficient conversion. However, there is limited research on the energy conversion in PTE detectors at micro/nano scale. In this study, we have achieved a two-order-of-magnitude enhancement in photovoltage responsivity in the self-rolled tubular tellurium (Te) photodetector with PTE effect. Under illumination, the tubular device demonstrates a maximum photovoltage responsivity of 252.13 V W−1 and a large detectivity of 1.48 × 1011Jones. We disclose the mechanism of the PTE conversion in the tubular structure with the assistance of theoretical simulation. In addition, the device exhibits excellent performances in wide-angle and polarization-dependent detection. This work presents an approach to remarkably improve the performance of photodetector by concentrating light and corresponding heat generated, and the proposed self-rolled devices thus hold remarkable promises for next-generation on-chip photodetection.

Optimal design of graphene-based plasmonic enhanced photodetector using PSO

In this paper, we report a graphene-based plasmonic photodetector optimized using the particle swarm optimization (PSO) algorithm and compatible with complementary metal–oxide–semiconductor (CMOS) technology. The proposed photodetector structure is designed to minimize fabrication challenges and reduce production costs compared to more complex alternatives. Graphene has been used for its unique properties in the detection region, titanium nitride (TiN) as a CMOS-compatible metal, and both to aid in plasmonic excitation. Photodetectors have key parameters influenced by multiple independent variables. However, practical constraints prevent thorough adjustment of all variables to achieve optimal parameter values, often resulting in analysis based on several simplified models. Here we optimize these variables by presenting a new approach in the field of photodetectors using the capabilities of the PSO algorithm. As a result, for the proposed device at the wavelength of 1550 nm, the voltage responsivity is 210.6215 V/W, the current responsivity is 3.7213 A/W, the ultra-compressed length is less than 3μm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu {\ ext{m}}$$\\end{document}, and the specific detectivity is 2.566×107\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${10}^{7}$$\\end{document} Jones were obtained. Furthermore, the device in question works under the photothermoelectric effect (PTE) at zero bias and has zero dark current, which ultimately resulted in a very low noise equivalent power (NEP) of 4.5361 pW/Hz\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{pW}}/\\sqrt{\ ext{Hz}}$$\\end{document}.

Effective Self‐Powered Semimetal TaTe2 Photodetector with the Thermal Localization Photothermoelectric Effect from Ultraviolet to Mid‐Infrared Range

AbstractUltra‐broadband photodetectors based on semimetal crystals have recently become popular because of their gapless band structures. In particular, semimetal crystals have large carrier mobility or high Seebeck coefficient; this almost eliminates the possibility of using semimetal crystals as photodetectors. In addition, a larger temperature gradient can cause photocurrent generation based on the photothermoelectric effect. Surprisingly, the TaTe2 crystal has a huge absorption coefficient (≈104 cm−1), a minimal specific heat (≈0.172 J g−1 K−1), and a low thermal conductivity (0.3 W m−1 K−1), which is beneficial for generating a high photothermal conversion efficiency of 30.2%, despite its small Seebeck coefficient, and achieving a large temperature gradient occurs for the heat generated by external illumination. Herein, the possibility of photoresponse based on the TaTe2 detector is explored, which has a low carrier mobility (≈10 cm2 V−1 s−1) and a small Seebeck coefficient (≈7.1 µV K−1). The self‐powered TaTe2 photodetector can also provide a competitive photoresponse range from 355 to 2715 nm and exhibit a maximum responsivity of 1.1 mA W−1 with a detectivity of 4.7 × 108 Jones at 455 nm. This study provides a new design scheme and operating mechanism for semimetal photodetectors and enriches semimetal crystal photodetectors.

Chiral photothermoelectric effect driven by high-Q quasi-bound states in the continuum

Bound states in continuum (BIC) have been proposed as a means to efficiently improve light-matter interactions in metasurfaces. While breaking the mirror symmetry of structure and developing BIC into a reachable and observable quasi-BIC, it is usually accompanied by the chiral phenomenon with high quality (Q) factor. Here, we report a spin-sensitive photodetector in the infrared (NIR) region comprising a silicon metasurface with chiral quasi-BIC, a silver layer, and a thermoelectric layer. A chiral quasi-BIC supported by a silicon metasurface can be realized under normal incidence. Based on finite element method simulations, a silicon metasurface with a silver layer shows a high Q-factor of 958.6 with a giant absorption circular dichroism of 0.83. Subsequently, we study the thermal performance of the chiral absorbers by using the heat transfer module of COMSOL. Combined with the thermoelectric material bismuth telluride, we calculate the differential photothermoelectric effects of the system under circular-polarized light irradiation. When the incident flux is 100 W cm−2, the output voltage under right-circular-polarization (left-circular-polarization) light reaches 0.59 mV (0.08 mV), which can be used for polarization detection. Therefore, our designed structure incorporating thermoelectricity broadens the applications of chiral BIC in sensors and detectors.

A Flexible and Wearable Photodetector Enabling Ultra-Broadband Imaging from Ultraviolet to Millimeter-Wave Regimes.

Flexible and miniaturized photodetectors, offering a fast response across the ultraviolet (UV) to millimeter (MM) wave spectrum, are crucial for applications like healthcare monitoring and wearable optoelectronics. Despite their potential, developing such photodetectors faces challenges due to the lack of suitable materials and operational mechanisms. Here, the study proposes a flexible photodetector composed of a monolayer graphene connected by two distinct metal electrodes. Through the photothermoelectric effect, these asymmetric electrodes induce electron flow within the graphene channel upon electromagnetic wave illumination, resulting in a compact device with ultra-broadband and rapid photoresponse. The devices, with footprints ranging from 3 × 20 µm2 to 50 × 20 µm2, operate across a spectrum from 325nm (UV) to 1.19mm (MM) wave. They demonstrate a responsivity (RV) of up to 396.4 ± 5.1mVW-1, a noise-equivalent power (NEP) of 8.6 ± 0.1 nW Hz- 0.5, and a response time as small as 0.8 ± 0.1ms. This device facilitates direct imaging of shielded objects and material differentiation under simulated human body-wearing conditions. The straightforward device architecture, aligned with its ultra-broadband operational frequency range, is anticipated to hold significant implications for the development of miniaturized, wearable, and portable photodetectors.

A bionic self-driven retinomorphic eye with ionogel photosynaptic retina.

Bioinspired bionic eyes should be self-driving, repairable and conformal to arbitrary geometries. Such eye would enable wide-field detection and efficient visual signal processing without requiring external energy, along with retinal transplantation by replacing dysfunctional photoreceptors with healthy ones for vision restoration. A variety of artificial eyes have been constructed with hemispherical silicon, perovskite and heterostructure photoreceptors, but creating zero-powered retinomorphic system with transplantable conformal features remains elusive. By combining neuromorphic principle with retinal and ionoelastomer engineering, we demonstrate a self-driven hemispherical retinomorphic eye with elastomeric retina made of ionogel heterojunction as photoreceptors. The receptor driven by photothermoelectric effect shows photoperception with broadband light detection (365 to 970 nm), wide field-of-view (180°) and photosynaptic (paired-pulse facilitation index, 153%) behaviors for biosimilar visual learning. The retinal photoreceptors are transplantable and conformal to any complex surface, enabling visual restoration for dynamic optical imaging and motion tracking.

Multi-Functional Actuators Made with Biomass-Based Graphene-Polymer Films for Intelligent Gesture Recognition and Multi-Mode Self-Powered Sensing.

Multi-functional actuation systems involve the mechanical integration of multiple actuation and sensor devices with external energy sources. The intricate combination makes it difficult to meet the requirements of lightweight. Hence, polypyrrole@graphene-bacterial cellulose (PPy@G-BC) films are proposed to construct multi-responsive and bilayer actuators integrated with multi-mode self-powered sensing function. The PPy@G-BC film not only exhibits good photo-thermoelectric (PTE) properties but also possesses good hydrophilicity and high Young's modulus. Thus, the PPy@G-BC films are used as active layers in multi-responsive bilayer actuators integrated with self-powered sensing functions. Here, two types of multi-functional actuators integrated with self-powered sensing functions is designed. One is a light-driven actuator that realizes the self-powered temperature sensing function through the PTE effect. Assisted by a machine learning algorithm, the self-powered bionic hand can realize intelligent gesture recognition with an accuracy rate of 96.8%. The other is humidity-driven actuators integrated a zinc-air battery, which can realize self-powered humidity sensing. Based on the above advantages, these two multi-functional actuators are ingeniously integrated into a single device, which can simultaneously perform self-powered temperature/humidity sensing while grasping objects. The highly integrated design enables the efficient utilization of environmental energy sources and complementary synergistic monitoring of multiple physical properties without increasing system complexity.

Photo-thermoelectric effect-driven detection of optical communication light in graphene/hBN heterostructures

We report on the photodetection properties of high-quality graphene encapsulated by hexagonal boron nitride under illumination with optical communication light. We demonstrate a gate-tunable photocurrent and zero-bias switching cycle operation at RT. Through gate and temperature-dependent photocurrent measurements, we determine that the dominant photoresponse mechanism is the photo-thermoelectric effect. At low temperatures, the photocurrent in finite doping regions correlates with the Seebeck coefficient, while sharp peaks emerge near the charge neutrality point due to an edge-excited photocurrent. Our study provides guidelines for high-performance graphene-based optoelectronic devices.

Photothermoelectric and Hydrovoltaic Effect Synergistic Multistage Core–Shell Structure Coated Fabrics of Flexible Fabricated Photothermoelectric Panels

Photothermoelectric and Hydrovoltaic Effect Synergistic Multistage Core–Shell Structure Coated Fabrics of Flexible Fabricated Photothermoelectric Panels