Interface-Located Photothermoelectric Effect of Organic Thermoelectric Materials in Enabling NIR Detection

the radiation emitted by the room-temperature object is mainly in the LWIR region, with the peak wavelength of about 10 µm. [1] Because of these two properties, photodetectors operating in the LWIR range are of significant importance for the heat-seeking technologies, such as all-weather surveillance, night vision, and missile guidance. To detect such lowenergy radiation by photon detectors, commonly used photosensitive materials are narrow-bandgap semiconductors (e.g., HgCdTe) and quantum wells (e.g., GaAs/ InGaAs). [2,3] For these photodetectors, the dark current at room temperature usually is large, and thus a cryogenic cooling unit is indispensable, which certainly increases the size and weight of photon detectors. Therefore, to miniaturize the volume and weight of LWIR detectors, the development of high-performance uncooled photodetectors is vital. Thermal detectors are well known for their ultra-broadband spectral response from UV to far-infrared and even to terahertz at room temperature. The excellent ability of terahertz radiation (0.1-1 mm) to penetrate through nonconducting materials renders it particularly attractive for applications in tomographic inspection. [4,5] Thermal detectors are based on the measurement of temperature-dependent properties, such as the resistance for bolometers, the temperature-difference-driven voltage for photothermoelectric (PTE) detectors, and the spontaneous polarization for pyroelectric (PE) detectors. The photoresponse in PE detectors depends on the variation of the spontaneous polarization vector with temperature; therefore, an external chopper is needed when measuring the power of continuous-wave (CW) radiation. For bolometers, an external bias is required, which introduces the extra 1/f noise. The typical temperature-sensitive materials in commercial bolometers are vanadium oxide (VO x ) or amorphous silicon. The main advantage of VO x lies in that its temperature coefficient of resistance is high (≈4% K −1 ) while the resistivity remains low, which is beneficial to reduce the noise level. [6] Detailed comparisons among different kinds of photodetectors are listed in Table 1.PTE detectors are based on the photothermal conversion and thermoelectric effect. As schematically shown in Figure 1, after absorbing the photons on one side of PTE detector, a temperature difference (ΔT) is built up, which drives the directed diffusion of charge carriers from the hot end to the cold end, establishing an electric potential difference (ΔU). This process High-performance uncooled photodetectors operating in the long-wavelength infrared and terahertz regimes are highly demanded in the military and civilian fields. Photothermoelectric (PTE) detectors, which combine photothermal and thermoelectric conversion processes, can realize ultra-broadband photodetection without the requirement of a cooling unit and external bias. In the last few decades, the responsivity and speed of PTE-based photodetectors have made impressive progress with the discovery of novel thermoelectric materials and ...

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Section: Bulk Materialsmentioning

confidence: 99%

“…Huang et al explored the PTE effect in poly[Cu x (Cu‐ethylenetetrathiolate)]‐based film. The PTE voltage depends strongly on the channel width.…”

Section: Bulk Materialsmentioning

confidence: 99%

Progress of Photodetectors Based on the Photothermoelectric Effect

et al. 2019

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“…Conventional thermoelectric materials employed in industrial production or fundamental researches are mainly focused on solid materials, including inorganic materials of Bi 2 Te 3 , PbTe, SiGe, skutterudite, half-Heusler alloys, Mg 2 (Si,Sn) solid solutions, [1][2][3][4][5] organic materials of poly(3-hexylthiophene), [6] poly(3,4-ethylenedioxyselenophene), [7] benzodifurandione based poly(p-phenylene vinylene) (BDPPV), [8] carbon materials of carbon nanotube, [9] graphene, [10] and organic-inorganic hybrid materials of MOF, [11] conducting polymers doped or intercalated with inorganic materials. [12,13] However, in the era of booming development on flexible electronics, solid materials have to overcome urgent challenges, including the lack of portability, bending ability, flexibility, and eco friendliness, for meeting various highlevel demands. Compared with solid materials, liquid materials intrinsically possess three attractive advantages consisting of excellent deformability, ease of doping, and self-healing abilities, which could afford great promise for flexible electronics.…”

mentioning

confidence: 99%

Flexible and Self‐Healing Thermoelectric Converters Based on Thermosensitive Liquids at Low Temperature Gradient

Jia

Tao

Wang

2016

Adv Elect Materials

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electrode surface. The mechanism of thermal harvesting is similar with thermal charge of ionic solution, which is confirmed by previous researches on non-redox ionic thermally capacitive cells. [26,27] It is of importance that Seebeck coefficient (S), power factor (PF), and thermoelectric figure of merit (ZT) are three important parameters used to evaluate the thermoelectric performance of potential thermoelectric materials. To maximize the thermoelectric performance, lower thermal conductivity ( ) κ , higher electrical conductivity (σ), and S are needed according to Equation (1)Herein, we designed a flexible and self-healing thermoelectric converter based on thermosensitive liquids with low temperature gradient. Ionic liquid acting as a thermosensitive fluid was employed owing to their intrinsic merits of liquid materials. The converter generates thermoelectric potential variation of tens of millivolt under low temperature gradient on account of asymmetrically heating. Notably, ionic liquids could also be integrated with flexible substrates or functional nanoparticles to render thermoelectric converter possessing the performance of flexibility, self-healing property, and photo-thermo-electric (PTE) conversion.Four imidazolium cations with different alkyl side chain and two anions including inorganic and organic species were combined to investigate thermoelectric performances of seven ionic liquids, excluding 1-ethyl-3-methyl imidazolium hexafluorophosphate ([EMIm][PF 6 ]) behaving as solid at room temperature. A measurement setup for monitoring the realtime change of open-circuit potential of ionic liquid thermoelectric converter (ILTE converter) was constructed to evaluate the S as shown in Figure 1a,b. The ILTE converter placed on two Peltier devices was heated at left end and kept the other end unheated at room temperature (25 °C). Temperature gradient between two ends of ILTE converter was well maintained owing to poor thermal conductivity of ionic liquid, confirmed by the measured thermal conductivity and thermal imaging of infrared camera (Table 1, Figure S8 and Movie S1, Supporting Information). Typical ILTE converter filled with [EMIm][Tf 2 N] was tested for potential variation generated from alternate heating and cooling of Peltier device (Figure 1c). The potential of left electrode immediately decreases when heated left end of converter. Clearly, this phenomenon results from the different ionic mobility, and cation-anion, ion-metal interactions. With unchanged ionic arrangement on right unheated electrode, ionic rearrangement, and migration on heated end lead to the change of open-circuit potential. The potential variation of converter as the value of 42.2 mV shows the approximately same value under fixed temperature gradient of 26.3 K for six cycles, Concerns of urgent global issues on energy crisis and sustainable development have pushed researchers to find new energy sources and novel strategies to utilize the waste energy in the ambient surroundings. Thermoelectric materials are a kind of promising...

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“…Basically, the temperature of cold junction is maintained at room temperature, while hot junction temperature is to be increased due to the electromagnetic heating. In literature, the effect combining optical and thermoelectric phenomena is called photothermoelectric, and it has been studied with the use of different advanced materials: graphene [10], single-layered MoS 2 [11], Bi 2 Se 3 nanoribbons [12], and organic thermoelectrics [13]. A line of works about THz detectors working on the TE effect have been published.…”

Section: Introductionmentioning

confidence: 99%

FEM Simulation of THz Detector Based on Sb and Bi88Sb12 Thermoelectric Thin Films

et al. 2020

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A terahertz (THz) detector based on thermoelectric thin films was simulated using the finite elements method. The thermoelectric circuit consisted of S b and B i 88 S b 12 150-nm films on the mica substrate. S b , B i 88 S b 12 , and mica-substrate properties have been measured experimentally in the THz frequency range. The model of electromagnetic heating was used in order to estimate possible heating of S b - B i 88 S b 12 contact. THz radiation power varied from 1 μ W to 50 mW, and frequency varied in the range from 0.3 to 0.5 THz. The calculations showed a temperature difference of up to 1 K, voltage up to 0.1 mV, and responsivity of several mVW − 1 . The results show that thin S b and B i − S b thermoelectric films can be used for THz radiation detection at room temperatures.

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Interface-Located Photothermoelectric Effect of Organic Thermoelectric Materials in Enabling NIR Detection

Cited by 48 publications

References 29 publications

Progress of Photodetectors Based on the Photothermoelectric Effect

Progress of Photodetectors Based on the Photothermoelectric Effect

Flexible and Self‐Healing Thermoelectric Converters Based on Thermosensitive Liquids at Low Temperature Gradient

FEM Simulation of THz Detector Based on Sb and Bi88Sb12 Thermoelectric Thin Films

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