Photothermoelectric Detectors Research Articles

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.

Touchless Thermosensation Enabled by Flexible Infrared Photothermoelectric Detector for Temperature Prewarning Function of Electronic Skin.

Artificial skin, endowed with the capability to perceive thermal stimuli without physical contact, will bring innovative interactive experiences into smart robotics and augmented reality. The implementation of touchless thermosensation, responding to both hot and cold stimuli, relies on the construction of a flexible infrared detector operating in the long-wavelength infrared range to capture the spontaneous thermal radiation. This imposes rigorous requirements on the photodetection performance and mechanical flexibility of the detector. Herein, a flexible and wearable infrared detector is presented, on basis of the photothermoelectric coupling of the tellurium-based thermoelectric multilayer film and the infrared-absorbing polyimide substrate. By suppressing the optical reflection loss and aligning the destructive interference position with the absorption peak of polyimide, the fabricated thermopile detector exhibits high sensitivity to the thermal radiation over a broad source temperature range from -50 to 110°C, even capable of resolving 0.05°C temperature change. Spatially resolved radiation distribution sensing is also achieved by constructing an integrated thermopile array. Furthermore, an established temperature prewarning system is demonstrated for soft robotic gripper, enabling the identification of noxious thermal stimuli in a contactless manner. A feasible strategy is offered here to integrate the infrared detection technique into the sensory modality of electronic skin.

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.

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.

Ion migration mediated high Seebeck effect in halide perovskites and application in infrared detection

Thermoelectric materials play an important role in thermopower systems, thermal sensing and infrared photo-thermoelectric imaging. Ionic thermoelectric materials have recently attracted attentions considering their relatively high Seebeck coefficient. However, the ionic thermoelectric materials have to use liquid or hydrogels for ion conduction, and are susceptible to leakage, evaporation and portability issues. Metal halide perovskites possess low thermal conductivity and prominent ion migration characteristics, making them theoretically suitable candidates for thermoelectric conversion. Here we present the first-ever study of the ionic thermoelectric properties in typical solid perovskite composition MAPbI3, revealing an extremely high Seebeck coefficient of 35.7 mV/K. Furthermore, the assembled photo-thermoelectric detector of carbon/MAPbI3 single crystal/carbon demonstrated a high response (0.58 V/W) toward infrared light and the imaging test was well resolved. This research provides a novel avenue to investigate efficient thermoelectric devices based on ionic and electronic mixed conductors and develop photo-thermoelectric applications.

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.

A thermocouple based on wideband hybrid metamaterial absorber for mid-infrared photo-thermoelectric detector

A mid-infrared (MIR) photo-thermoelectric (PTE) detector is proposed based on a hybrid thermocouple consisting of a wideband metamaterial absorber and Seebeck material. When a mid-infrared wave illuminates the detector, the incident energy of the MIR beam is efficiently detected in this process of converting the energy of the light wave into the absorbed heat firstly by the wideband metamaterial absorber, and then outputting a voltage change according to the variation in temperature by a semiconductor material with a high Seebeck coefficient. Because of the existence of the metamaterial absorber, the high absorptions are almost achieved at a wide wavelength range from 3.4μm to 4.8μm with the absorptivity over 80%, and the average absorptivity is 93.6%. Meanwhile, the perfect absorptions appear at the wavelengths of 3.6μm, 4μm and 4.4μm. Comparing with the other reported detectors based on black materials and multilayer resonant cavities, this metamaterial absorber has a high absorptivity as well as a wide bandwidth, facilitating the maximum responsivity of single thermocouple as high as 0.89V/W. This hybrid thermocouple is able to operate at room temperature and has the advantages of angle insensitivity, simple in structure and easy integration, which has good potential applications in mid-infrared detection, sensing and imaging.

Long-wave infrared photothermoelectric detectors with ultrahigh polarization sensitivity

Filter-free miniaturized polarization-sensitive photodetectors have important applications in the next-generation on-chip polarimeters. However, their polarization sensitivity is thus far limited by the intrinsic low diattenuation and inefficient photon-to-electron conversion. Here, we implement experimentally a miniaturized detector based on one-dimensional tellurium nanoribbon, which can significantly improve the photothermoelectric responses by translating the polarization-sensitive absorption into a large temperature gradient together with the finite-size effect of a perfect plasmonic absorber. Our devices exhibit a zero-bias responsivity of 410 V/W and an ultrahigh polarization ratio (2.5 × 104), as well as a peak polarization angle sensitivity of 7.10 V/W•degree, which is one order of magnitude higher than those reported in the literature. Full linear polarimetry detection is also achieved with the proposed device in a simple geometrical configuration. Polarization-coded communication and optical strain measurement are demonstrated showing the great potential of the proposed devices. Our work presents a feasible solution for miniaturized room-temperature infrared photodetectors with ultrahigh polarization sensitivity.

Capillary‐Assisted Self‐Assembly of Carbon Nanotubes for the Self‐Powered Photothermoelectric Detector

The development of mid‐infrared (MIR) detectors has become a hot research topic with significant progress in low‐dimensional materials and clean‐room fabrication strategies. Some of the applications of MIR detectors include industrial non‐destructive testing, wearable safety monitoring, and other Internet of Things. Photothermoelectric (PTE) mechanism, as a room‐temperature free‐bias conversion mode, is comprehensively developed in the MIR regimes in the last decade. Although carbon nanotubes (CNTs) and their related materials are demonstrated as effective PTE conversion materials, the large‐area scalable detector fabrication based on the Si substrate is still underdeveloped, thus limiting further PTE device designs and industrial applications. Herein, the self‐assembly CNT‐based detectors driven by the capillary force are fabricated to achieve sensitive and rapid IR detection, and photoresponse measurements of PTE detectors are experimentally performed at room temperature and atmospheric conditions. This work reveals that the PTE mechanism can play a key role in the IR response, thereby broadening horizons about high‐performance IR detectors in industrial applications.

An infrared photothermoelectric detector enabled by MXene and PEDOT:PSS composite for noncontact fingertip tracking

Photothermoelectric (PTE) detectors functioning on the infrared spectrum show much potential for use in many fields, such as energy harvesting, nondestructive monitoring, and imaging fields. Recent advances in low-dimensional and semiconductor materials research have facilitated new opportunities for PTE detectors to be applied in material and structural design. However, these materials applied in PTE detectors face some challenges, such as unstable properties, high infrared reflection, and miniaturization issues. Herein, we report our fabrication of scalable bias-free PTE detectors based on Ti3C2 and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) composites and characterization of their composite morphology and broadband photoresponse. We also discuss various PTE engineering strategies, including substrate choices, electrode types, deposition methods, and vacuum conditions. Furthermore, we simulate metamaterials using different materials and hole sizes and fabricated a gold metamaterial with a bottom-up configuration by simultaneously combining MXene and polymer, which achieved an infrared photoresponse enhancement. Finally, we demonstrate a fingertip gesture response using the metamaterial-integrated PTE detector. This research proposes numerous implications of MXene and its related composites for wearable devices and Internet of Things (IoT) applications, such as the continuous biomedical tracking of human health conditions.

Flexible Multi-Element Photothermoelectric Detectors Based on Spray-Coated Graphene/Polyethylenimine Composites for Nondestructive Testing

Photothermoelectric (PTE) detectors receive much attention owing to the superiority of self-powered, non-bias input, and friendly ambient environments, facilitating abundant prospective applications in industrial inspection, medical diagnostics, homeland security, and wearable Internet of Things. However, many drawbacks of currently applicable PTE materials, involving unstable material oxidation, an uncontrollable fabrication process, and unscalable manufacturing, hinder the development of industrial productions. Herein, we demonstrate a vertical graphene/polyethylenimine composite PTE detector fabricated with an optimized spray-coating method in compact alignment on various surfaces, achieving a significant photovoltage detectivity and responsivity of 6.05 × 107 cm Hz1/2 W-1 and 2.7 V W-1 response at a 973 K blackbody temperature radiation (2.98 μm peak wavelength). In addition, the long-term stability and resistible concave and convex bending flexibility are presented. Furthermore, a nondestructive testing system is established and verified through high-spatial-resolution and high-penetration illustration. Overall, the spray-coated and flexible PTE graphene/polyethylenimine multi-elements with broadband infrared absorption compatibility and stable energy conversion are promising candidates for future health monitoring and wearable electronics.

Low-noise room-temperature terahertz detector based on the photothermoelectric effect of graphene oxide-Bi films

Graphene has a very wide range of applications in terahertz (THz) photothermoelectric (PTE) detection due to its unique optical properties, but its high thermal conductivity leads to less than ideal performance of graphene PTE detectors. We experimentally demonstrate a method using UV/ozone to oxidize graphene, breaking the C–C bond by UV irradiation on the graphene surface and reacting with the excited oxygen atoms to promote the release of CO2, CO gas from the surface defects to produce hole structures by oxidative etching of graphene. Bi was assembled at the surface defects by liquid phase treatment to form graphene oxide (GO) - Bi films. The surface feature morphology was analyzed by SEM and XPS, and the optimal treatment time was found by setting control groups (G-0 to G-5) for UV/ozone oxidation. The devices are able to achieve a responsivity of 0.226 V/W for 0.22 THz and a value of NEP about 1.34 nW/√Hz. Simple preparation method provides new ideas for designing terahertz detectors.

System design of large-area vertical photothermoelectric detectors based on carbon nanotube forests with MXene electrodes.

Photothermoelectric (PTE) detectors that combine photothermal and thermoelectric conversion have emerged in recent years. They can overcome bandgap limitations and achieve effective infrared detection. However, the development of PTE detectors and the related system design are in the early phases. Herein, we present vertical PTE detectors utilizing the active layer of carbon nanotube forests with MXenes acting as top electrodes. The detector demonstrates its capacity for sensitive infrared detection and rapid infrared response. We also investigated the relationship between photoresponse and different MXene electrode types as well as their thickness, which guides the PTE detector configuration design. Furthermore, we packed the PTE detectors with a polytetrafluoroethylene (PTFE, Teflon) cavity. The photoresponse is improved and the degradation is significantly delayed. We also applied this PTE detector system for non-destructive tracking (NDT) applications, where the photovoltage mapping pattern proves the viability of the imaging track. This work paves the way toward infrared energy harvesters and customized industrial NDT measurement.

Fast optical‐writing recognition based on two‐dimensional photothermoelectric effect assisted with deep learning

AbstractThe photothermoelectric (PTE) effect enables a simple structure to construct a noncontact and self‐powered writing device. PTE detectors based on active materials and one‐dimensional (1D) position‐sensitive PTE effect have attracted considerable attentions. However, there is no research on applying the 1D position‐sensitive PTE effect to a two‐dimensional (2D) surface. Besides, flexible writing devices based on the PTE effect have not been reported. Here, we demonstrate a self‐powered flexible optical writing device based on the 2D position‐sensitive PTE effect of SnSe thin film. Laser positioning, tracking, and distinguishing of optically written characters have been realized by only measuring the bi‐directional output voltages during the writing process. A deep convolutional neural network has been introduced to recognize optically written numbers and characters with high recognition accuracy (92%) and fast processing speed (8.6 ms). The flexible optical‐writing device with a simple structure could rapidly and accurately recognize characters in a noncontact fashion using a small amount of training data.image

Photothermal‐Induced Electrical Behavior of Micron‐Sized Platinum Structures and Their Efficient Photodetection

Photothermal effects have recently been widely investigated for applications in the fields of biomedicine, physics, and chemistry. Unfortunately, only a few reports describe their potential use in ultrafast photodetectors. Herein, direct evidence for ultrafast photothermal‐induced electrical behavior of a platinum microwire (Pt MW) illuminated by a focused laser beam and modulated at different frequencies (329 Hz, 10, 50, and 150 kHz) is provided. The obtained electrical behavior images indicate that Pt‐based structures can be used to develop a new type of photodetector, namely, a photo‐thermo‐electric (PTE) detector. A high photoresponsivity of 0.3 mA W−1 and a fast response time of ≈50 μs on a single 1 μm wide Pt PTE detector are obtained. To further amplify the PTE effect of Pt MW, an integrated array of Pt MWs and a coating of gold nanorods is combined into a hybrid PTE detector, achieving a higher responsivity close to 100 mA W−1, which is 300 times higher than that of a single Pt MW PTE detector. These results confirm that Pt‐based PTE devices are promising candidates for efficient and fast‐response photodetectors.

Ultra-broadband SnSe-based photothermoelectric detector for mid-infrared gas spectroscopy

Seebeck effect is one of the desirable pathways for developing advanced room-temperature (RT) broadband photothermoelectric (PTE) detectors, which are important for infrared spectroscopy applications. However, achieving high performance PTE detectors utilizing materials with high Seebeck coefficient remains a great challenge and further improvements are highly desired. Herein, we introduce a layered material SnSe with high Seebeck coefficient up to 507 ± 20 μV K−1 and further demonstrate an RT ultra-broadband PTE detector ranging from a visible region to a mid-infrared (MIR) region (0.532–13.2 μm). The detector yields a high responsivity of 0.47 V W−1 and a moderate response speed of 107 ms at an excitation wavelength of 8.1 μm at zero bias, which is comparable or higher than those parameters of the commercial products. Moreover, we have retrieved absorption fingerprints of molecular gases during MIR spectroscopy by using this detector owing to its wide response range, which illustrates great potential of this type of broadband high performance PTE detector toward advanced optoelectronics applications.

On-chip mid-infrared photothermoelectric detectors for full-Stokes detection

On-chip polarimeters are highly desirable for the next-generation ultra-compact optical and optoelectronic systems. Polarization-sensitive photodetectors relying on anisotropic absorption of natural/artificial materials have emerged as a promising candidate for on-chip polarimeters owing to their filterless configurations. However, these photodetectors can only be applied for detection of either linearly or circularly polarized light, not applicable for full-Stokes detection. Here, we propose and demonstrate three-ports polarimeters comprising on-chip chiral plasmonic metamaterial-mediated mid-infrared photodetectors for full-Stokes detection. By manipulating the spatial distribution of chiral metamaterials, we could convert polarization-resolved absorptions to corresponding polarization-resolved photovoltages of three ports through the photothermoelectric effect. We utilize the developed polarimeter in an imaging demonstration showing reliable ability for polarization reconstruction. Our work provides an alternative strategy for developing polarization-resolved photodetectors with a bandgap-independent operation range in the mid-infrared.

SrTiO3/CuNi‐Heterostructure‐Based Thermopile for Sensitive Human Radiation Detection and Noncontact Human–Machine Interaction

AbstractNoncontact interactive technology provides an intelligent solution to mitigate public health risks from cross‐infection in the era of COVID‐19. The utilization of human radiation as a stimulus source is conducive to the implementation of low‐power, robust noncontact human–machine interaction. However, the low radiation intensity emitted by humans puts forward a high demand for photodetection performance. Here, a SrTiO3−x/CuNi‐heterostructure‐based thermopile is constructed, which features the combination of high thermoelectric performance and near‐unity long‐wave infrared absorption, to realize the self‐powered detection of human radiation. The response level of this thermopile to human radiation is orders of magnitude higher than those of low‐dimensional‐materials‐based photothermoelectric detectors and even commercial thermopiles. Furthermore, a touchless input device based on the thermopile array is developed, which can recognize hand gestures, numbers, and letters in real‐time. This work offers a reliable strategy to integrate the spontaneous human radiation into noncontact human–machine interaction systems.

Large-Area, Flexible, and Dual-Source Co-Evaporated Cs3Cu2I5 Nanolayer to Construct Ultra-Broadband Photothermoelectric Detector from Visible to Terahertz

Large-Area, Flexible, and Dual-Source Co-Evaporated Cs₃Cu₂I₅ Nanolayer to Construct Ultra-Broadband Photothermoelectric Detector from Visible to Terahertz

Design of room-temperature infrared photothermoelectric detectors based on CNT/PEDOT:PSS composites

Self-powered, flexible, and uncooled mid-wavelength infrared (MWIR) detectors based on the photothermoelectric (PTE) mechanism are promising for the next-generation wearable Internet of Things (IoT).