Photothermoelectric Research Articles

Strong Anisotropy and Giant Photothermoelectricity of 1D Alloy Nb3Se12I-Based Photodetector for Ultrabroadband Light-Detection and Encryption Imaging Application.

Securing high-capacity and safe communication holds great potential for ushering in the new era of digital society. In this study, a wide-band photodetector based on the quasi-1D niobium selenide compounds (Nb3Se12I), showing up photothermoelectric (PTE) dominated multiple synergistic effects with high responsivity across a wide wavelength range from deep-ultraviolet (254nm) to terahertz (0.30 THz), providing an efficient strategy for high-capacity optical processing is introduced. Combined with the polarized-sensitive property of the Nb3Se12I photodetector, an encrypted imaging technology using polarization-resolved PTE current is developed. This technology is capable of transforming encrypted messages into polarization states, which can be restored through a specially designed decryption algorithm, greatly enhancing the concealment and security of the information transmission process. Overall, the Nb3Se12I-based detector manifests in terms of high responsivity (283.2 A W-1 to 520nm, 1632.4 A W-1 to 980nm, and 1868.1 A W-1 for short-wave infrared light of 2200nm), suitable response speed of 43 µs for 0.30 THz wave and polarization anisotropy ratio of 1.83. The versatile abilities of photodetector in the realm of ultrabroadband polarized detection and encryption imaging may advance the use of anisotropic thermoelectric materials in high-capacity and secure information communication applications.

Decipher the Wavelength and Intensity Using Photothermoelectric Detectors.

Broadband photodetectors that can decipher the wavelength (λ) and intensity (I) of an unknown incident light are urgently demanded. Photothermoelectric (PTE) detectors can achieve ultrabroadband photodetection surpassing the bandgap limitation; however, their practical application is severely hampered by the lack of deciphering strategy. In this work, we report a variable elimination method to decipher λ and I of the incident lights based on an integrated Ag2Se film-based PTE detector. Nanostructured Ag2Se films with controlled thickness are synthesized using an ion sputtering of Ag and a room-temperature selenization method and then assembled into a detector. Under identical illumination, Ag2Se films of different thicknesses produce varying output photothermal voltages, influenced by factors including λ. By establishing a direct relationship between the photothermal voltage and the absorption of Ag2Se films of varied thickness, we successfully eliminate variables independent of λ, thus determining λ. Subsequently, I is determined by the calibrated responsivity relationship using obtained λ. Our PTE detector achieves a broadband spectrum from 400 to 950 nm and high accuracy, with deviations as low as ∼2.63 and ∼0.53% for deciphered λ and I, respectively. This method allows for self-powered broadband decipherable photodetection without a complex device architecture or computational assistance, which could boost the research enthusiasm and promote the commercialization of PTE broadband detectors.

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

Light-Cured Junction Formation and Broad-Band Imaging Application in Thermally Mismatched van der Waals Heterointerface.

Van der Waals (vdW) heterostructures are mainly fabricated by a classic dry transfer procedure, but the interface quality is often subject to the vdW gap, residual strains, and defect species. The realization of interface fusion and repair holds significant implications for the modulation of multiple photoelectric conversion processes. In this work, we propose a thermally mismatched strategy to trigger broad-band and high-speed photodetection performance based on a type-I heterostructure composed of black phosphorus (BP) and FePS3 (FPS) nanoflakes. The BP acts as photothermal source to promote interface fusion when large optical power is adopted. The regulation of optical power enables the device from pyroelectric (PE) and/or alternating current photovoltaic (AC-PV) mode to a mixed photovoltaic (PV)/photothermoelectric (PTE)/PE mode. The fused heterostructure device presents an extended detection range (405~980 nm) for the FPS. The maximum responsivity and detectivity are 329.86 mA/W and 6.95 × 1010 Jones, respectively, and the corresponding external quantum efficiency (EQE) approaches ~100%. Thanks to these thermally-related photoelectric conversion mechanism, the response and decay time constants of device are as fast as 290 μs and 265 μs, respectively, superior to current all FPS-based photodetectors. The robust environmental durability also renders itself as a high-speed and broad-band imaging sensor.

Ultrahigh-response flexible photothermoelectric photodetectors based on a graded Bi2Te3-carbon nanotube hybrid

Photothermoelectric (PTE) detectors can work in a broad band range without using a cooling unit and external bias and therefore have attracted intense research interest. However, the performance of PTE detectors constructed using traditional TE materials has been limited by their poor optical absorption and intrinsic brittleness. We report a flexible graded TE material comprised of Bi2Te3 nanocrystals adsorbed on a single-wall carbon nanotube (SWCNT) network, which has excellent flexibility, high photo-thermal conversion ability and good TE properties. Flexible PTE detectors were constructed, and had an ultrahigh responsivity of 0.71 V/W, a high peak detectivity up to 2.1 × 108 Jones, and a broad response band ranging from the infrared to the terahertz band. The excellent PTE performance of the detectors is attributed to the broadband optical absorption of SWCNTs, the high TE performance of Bi2Te3 nanocrystals, and the graded layer structure of the hybrid.

Four-channel graphene optical receiver

Abstract Silicon photonics with the advantages of low power consumption and low fabrication cost is a crucial technology for facilitating high-capacity optical communications and interconnects. The graphene photodetectors (GPDs) featuring broadband operation, high speed, and low integration cost can be good additions to the SiGe photodetectors, supporting high-speed photodetection in wavelength bands beyond 1.6 μm on silicon. Here we realize a silicon-integrated four-channel wavelength division multiplexing (WDM) optical receiver based on a micro-ring resonator (MRR) array and four p-n homojunction GPDs. These photo-thermoelectric (PTE) GPDs exhibit zero-bias responsivities of ∼1.1 V W−1 and set-up limited 3 dB-bandwidth >67 GHz. The GPDs show good consistence benefiting from the compact active region array (0.006 mm2) covered by a single mechanically exfoliated hBN/graphene/hBN stack. Moreover, the WDM graphene optical receiver realized 4 × 16 Gbps non-return-to-zero optical signal transmission. To the best of our knowledge, it is the first GPD-array-based optical receiver using high-quality mechanically exfoliated graphene and edge graphene-metal contacts with low resistances. Apparently, our design is also compatible with CVD-grown graphene. This work sheds light on the large-scale integration of GPDs with high consistency and uniformity, enabling the application of high-quality mechanically exfoliated graphene, and promoting the development of the graphene photonic integrated circuits.

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.

Thermoelectric-Feedback Nanocomposite Hydrogel for Temperature-Synchronized Monitoring and Regulation in Accurate Photothermal Therapy.

Photothermal therapy (PTT) is a promising approach for tumor ablation and cancer treatment. However, controlling the therapeutic temperature during treatment remains challenging, and imprecise thermal regulation can harm adjacent healthy tissues, reduce therapeutic accuracy, and promote the thermotolerance of cellular phenotypes, potentially leading to tumor invasion and recurrence. Although existing methods provide basic temperature control by adjusting irradiation power and photothermal agent dosing, they lack real-time temperature monitoring and feedback control capabilities, underscoring the urgent need for more integrated and precise PTT systems. In this context, an innovative photothermoelectric (PTE) cobalt-infused chitosan (CS) nanocomposite hydrogel (PTE-Co@CS) is developed for precise temperature-regulated PTT, exhibiting desirable mechanical properties and exceptional biocompatibility. Enhanced by embedded nanoparticles, PTE-Co@CS demonstrates superior photothermal conversion efficiency compared with existing methods, while also featuring thermoelectric responsiveness and increased sensitivity to photostimuli. Its advantageous PTE response characteristics ensure a linear correlation between temperature shifts and resistance changes (e.g., R2 = 0.99919 at 0.5Wcm⁻2), enabling synchronized qualitative and quantitative control of PTT temperature through electrical signal monitoring. This allows for real-time monitoring and regulation during PTT, effectively addressing the issue of uncontrollable temperatures and improving therapeutic efficacy.

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.

All-Automated Fabrication of Freestanding and Scalable Photo-Thermoelectric Devices with High Performance.

Flexible photo-thermoelectric (PTE) devices have great application prospects in the fields of solar energy conversion, ultrabroadband light detection, etc. A suitable manufacturing process to avoid the substrate effects as well as to create a narrow transition area between p-n modules for high-performance freestanding flexible PTE devices is highly desired. Herein, an automated laser fabrication (ALF) method is reported to construct the PTE devices with rylene-diimide-doped n-type single-walled carbon nanotube (SWCNT) films. Thewet-compressing approach is developed to improve the thermoelectric power factors and figure of merit (ZT) of the SWCNT hybrid films. Then, the films are cut and patterned automatically to make PTE devices with various structures by the proposed ALF method. The freestanding PTE device with a narrow transition area of ≈2-3 µm between the p and n modules exhibits a high-power density of 0.32 µW cm-2 under the light of 200 mW cm-2, which is among the highest level for freestanding-film-based PTE devices. The results pave the way for the automatic production process of PTE devices for green power generation and ultrabroadband light detection.

2D Materials for Photothermoelectric Detectors: Mechanisms, Materials, and Devices

Abstract2D materials, with outstanding optical, thermal, and electric properties, are emerging as promising candidates for fabricating high‐performance photodetectors. Recently, impressive progresses have been made in this area and some challenges are remaining to improve the properties of photodetectors. As one important part in the mainstream photodetection mechanisms, photothermoelectric (PTE) effect is showing unique priorities in fabricating advanced photodetectors, especially broadband detection operating in the mid‐infrared and terahertz spectral regime. Here, recent progress on PTE photodetectors based on layered 2D materials is reviewed. The physical mechanism of PTE effect is first discussed and then the optical and thermoelectric properties of various 2D materials are analyzed. Furthermore, strategies to improve the photodetection performance of PTE detectors are summarized in two major categories including enhanced photothermal conversion and thermoelectric conversion processes. Finally, the challenges and prospects for future research in 2D thermoelectric materials and PTE detectors are also provided.

Pulse irradiation synthesis of metal chalcogenides on flexible substrates for enhanced photothermoelectric performance

High synthesis temperatures and specific growth substrates are typically required to obtain crystalline or oriented inorganic functional thin films, posing a significant challenge for their utilization in large-scale, low-cost (opto-)electronic applications on conventional flexible substrates. Here, we explore a pulse irradiation synthesis (PIS) to prepare thermoelectric metal chalcogenide (e.g., Bi2Se3, SnSe2, and Bi2Te3) films on multiple polymeric substrates. The self-propagating combustion process enables PIS to achieve a synthesis temperature as low as 150 °C, with an ultrafast reaction completed within one second. Beyond the photothermoelectric (PTE) property, the thermal coupling between polymeric substrates and bismuth selenide films is also examined to enhance the PTE performance, resulting in a responsivity of 71.9 V/W and a response time of less than 50 ms at 1550 nm, surpassing most of its counterparts. This PIS platform offers a promising route for realizing flexible PTE or thermoelectric devices in an energy-, time-, and cost-efficient manner.

Boosted photothermoelectric effect in silver nanoparticles decorated carbon nanotube films for infrared detection and actuation

Photothermoelectric (PTE) effect provides a platform for utilization both photon and thermal energy, giving rise to high-performance photodetector and radiation energy harvester. Carbon nanotube (CNT)/metal heterojunction has been demonstrated to be capable of boosting power generation based on PTE effect, and yet the responsivity and detectivity are inferior to those based on conventional optoelectronic effect. Herein, CNT films decorated by Ag nanoparticles (NPs) forming Ag/CNT heterojunctions have been investigated, showing both excellent photothermal and power conversion capability under infrared (IR) illumination. Ultrahigh ΔT of 196.4 K, maximum output voltage of 15.74 mV and power of 9.94 μW have been achieved under IR laser illumination at power density of 7.65 W/cm2, which are superior to reported photodetectors based on PTE effect. CNT@Ag NPs film possesses competitive photodetection performance as well, with responsivity and detectivity of 107 mV/W and 947.68 MHz1/2/W, respectively. Furthermore, when integrated with polydimethylsiloxane, an IR laser actuated movement function mimicking caterpillar has been realized. Our study thus expands the diverse functions of CNT-based films utilizing PTE effect toward applications in IR detection, radiation energy harvesting and soft actuation.

High-performance flexible SnS photothermoelectric photodetector for temperature sensing function

The photothermoelectric (PTE) photodetector (PD) is crucial for realizing broadband detection, which is vital for the next generation of integrated multifunctional photodetectors. Due to the limitation of material band gap...

Long-wave infrared photothermoelectric detectors with resonant nanophotonics

Photothermoelectric (PTE) detectors, renowned for their ultra-broadband photodetection capabilities at room temperature without requiring an external power supply, are pivotal for advancing infrared and terahertz detection technologies. Despite significant advancements...

Terahertz detector based on Bi1-xSbx/Cu thermoelectric branches

Although most types of room-temperature THz detectors involving photothermoelectric (PTE) elements operate in a relatively narrow frequency band due to their antenna-coupled structure, such detectors may be implemented on the basis of non-resonant structures with broadband response due to broadband nature of PTE effect. This work is devoted to improvement of PTE detector sensitivity using serial connection of PTE elements consisting of bismuth-antimony thin films and Cu electrodes. The responsivity of this detector is studied at the frequency of 140 GHz. It is shown that the average voltage produced by PTE detector reaches up to 0.6 mV and is 15 times higher than one produced by continuous film consisting of the same material, while the maximum rate of voltage change is 17 times higher in comparison with continuous film response. Noise equivalent power (NEP) of PTE detector based on Bi1-xSbx/Cu branches is equal to 12.6 nWHz−0.5, and noise equivalent temperature difference (NETD) is equal to 4.9 m °C. This detector may be applied in the field of THz and microwave photonics in scanning security systems, THz signal detection in wireless communications, imaging and diagnostics in medicine, food industry and material characterization.

Simple Non‐Destructive and 3D Multi‐Layer Visual Hull Reconstruction with an Ultrabroadband Carbon Nanotubes Photo‐Imager

AbstractWhile millimeter‐wave (MMW)–infrared (IR) broad photo‐imaging exhibits significant potential as an inspection technique, photo‐thermoelectric (PTE) detector operations employing carbon nanotubes (CNTs) are highly suitable because of their efficient absorption characteristics in the above bands. Such an imaging device design and the associated material coordination allow the aggregation of multiple wavelength‐specific optical information for the constituent identification of target objects in a non‐destructive manner with high sensitivity. On the other side, computer vision techniques facilitate 3D structure reconstruction as approaches from inspection methodologies, in addition to the aforementioned imaging device design. Although non‐destructive inspections require collectively satisfying both constituent identification and structural reconstruction, investigations combining MMW–IR broad photo imaging and computer vision monitoring are still insufficient. This work demonstrates computer vision‐driven simple 3D composite multi‐layer reconstructions via non‐destructive broadband multiple‐wavelength monitoring with the CNT film PTE imager. Visual hull evaluation, which is one of the representative computer vision techniques, converts 2D transmissive PTE images with different viewpoints into 3D reconstruction models. The subsequential graphical superposition of these wavelength‐specific models results in non‐destructive entire reconstructions of 3D composite multi‐layer target objects. Therefore, the present computer vision‐driven PTE broadband 3D reconstruction bridges the gap between methodologies and device design strategies toward non‐destructive inspection applications.

Room-ambient operation of integrated and visualized photothermoelectric system with patterned Mo2C/PEDOT: PSS flexible devices

Photothermoelectric (PTE) devices have emerged as highly promising technological advancements in energy harvesting and electronics. However, the development of PTE devices faces challenges in achieving exceptional performance, adaptable flexibility, durable stability, and compatibility within a system. This study proposes a self-powered PTE device that operates at room temperature by integrating molybdenum carbide (Mo2C)/ Poly(3,4-ethylene-dioxythiophene)-poly (styrene sulfonate) (PEDOT: PSS) nanomaterials with a flexible poly (ethylene terephthalate) (PET) substrate. We achieve precise control over the device size through a spray coating technique and employ a laser-involved mask technique for efficient fabrication. Our Mo2C/PEDOT: PSS devices demonstrate remarkable long-term stability and outstanding flexibility and can be folded and twisted without increasing performance degradation. The devices exhibit a responsivity of 4.2 V W−1 and a detectivity of 1.2 × 108 cm Hz1/2 W−1 at 973 K black-body radiation. By employing these advantages, we integrate two potential systems—the motion tracking system and the non-destructive (NDT) imaging system—that showcase time-tracking of human radiation and high-resolution imaging. These promising platforms expand the potential of PTE technology into diverse applications, including industry, aerospace, public health, security, and wearable monitoring.

Spiral room-temperature thin-filmed photo-thermoelectric THz detector based on Bi88Sb12 solid solutions

A terahertz (THz) room-temperature photo-thermoelectric (PTE) detector based on elements of spiral shape has been proposed. The units have been fabricated on a 20 μm mica substrate from 150 nm thin films of Bi88Sb12 and copper by a thermal deposition technique. Thermoelectric Bi88Sb12 leg acted as a sensitive element due to its high absorption and spiral shape that enable heating. It also acts as a radiator to maintain a temperature difference and a thermo-electromotive force formation. A prototype of a PTE detector has been designed, fabricated, and tested at the 0.14 THz radiation frequency. Measurements showed a voltage signal of 275 μV from 1 unit, the responsivity of 50.7 mV/W. It showed a noise equivalent power of 158 nW Hz−1/2, which is 1–2 orders of magnitude higher than for bolometers and Golay cells, but is comparable with pyroelectric detectors. The response time was 2.21 s and 1.75 s according to the experiment and the simulation, respectively, which is a bit better than for pyroelectric detectors. Based on numerical simulation an improved detector design has been proposed allowing the voltage up to 800 μV from 1 unit. The proposed PTE detector possesses several significant advantages resulting from the usage of Bi88Sb12 and comprehensive design. The fabrication process is fast, low-cost, and CMOS-compatible. The design is compact and simple and requires only two materials that simultaneously act as an absorber, thermocouple, electrical contacts, and radiator. The detector operates at room temperature and can be applied in 6 G communication systems, imaging and medical diagnostics.

All‐Screen‐Coatable Photo‐Thermoelectric Imagers for Physical and Thermal Durability Enhancement

AbstractCarbon nanotube (CNT) film photo‐thermoelectric (PTE) imagers are suitable for non‐destructive inspection techniques owing to their functionalities. Simultaneously, their practical application remains a crucial bottleneck due to low yield handling in the device fabrication (e.g., disconnections between photo absorbent channels and readout electrodes). However, studies clarifying the above malfunction mechanism and associated dominant factors in device handling, such as specific fabrication or material selection steps, still need to be completed. To address this issue, this work introduces all‐screen‐coatable fabrication techniques for CNT film PTE imagers to enhance their physical and thermal durabilities. First, this work determined that the transfer of CNT films on supporting substrates dominantly governs the mechanical robustness of the channels and that thermal curing in the subsequent fabrication process is an essential factor in the yields of channel‐electrode connections. The proposed approach ensures a transfer‐free direct coating of the CNT film on diverse substrates and is sufficiently durable against thermal curing‐induced disconnections at the channel‐electrode interfaces. The screen‐coating technique is also available for whole device materials of solution‐processable CNT film PTE imagers, simplifying fabrication processes. All‐screen‐coatable CNT film PTE imagers synergize their inherent functional sensing and high‐yield operations toward versatile applications.