Academic literature on the topic 'Photo-thermoelectric generators'

Zinc oxide ceramics exhibit various semiconductor properties through optimized elements or materials doping. The elements doping of aluminum or gallium can control the electric conductivity, and composites doping of indium and rare earth such as yttrium can increase the thermoelectric conversion efficiency. In this investigation, dendritic lattice structures of the zinc oxide semiconductors with periodically ordered arrangements or self similar patterns were fabricated successfully to increase the surfaces area and porosity values by using micro patterning stereolithography of a computer aided design and manufacturing. These semiconductor dendrites with penetrable paths and extensive interfaces will be used for fluid and heat flow receptors and applied to the novel sensor devices and energy generators. The dendritic lattice models sliced into a series of cross sectional patterns with uniform thickness by using a stereolithographic file format convertor. These numerical data were transferred into the micro processing equipment. High viscosity slurry material was prepared through the mixing of photo sensitive acrylic resin and the zinc oxide particle at 30 % in volume fraction. The slurry was supplied on a flat substrate with 8 μm in layer thickness by using a mechanical knife edge. The cross sectional image was exposed on the slurry surface by using digital micro mirror devices. Through the layer by layer processes, the solid component was obtained with micrometer order part accuracies. The dense ceramic sample was purchase after de-waxing and sintering process.

Silicon tin (Si1−x Sn x ) binary alloys are attractive materials for next-generation Si-based photonics and thermoelectronics. The energy band calculations predicted that the conduction band at the Γ point is more rapidly decreased than the others by the Sn substitution, and direct band gap semiconductors can be realized at more than sufficient Sn content [1], although they varied from 25 to 90% by the calculation methods. The corresponding wavelength range will be matched to the optical communication band, suggesting Si1−x Sn x can be applied to near-infrared light source and detector. Another interest is the dramatic reduction of the thermal conductivity by the Sn substitution owing to the mass-difference phonon scattering. Theoretically [2], the thermal conductivity of bulk Si (145 Wm−1K−1 [3]) can be decreased to ~5 Wm−1K−1 by the 10% Sn substitution; the lowest thermal conductivity (3 Wm−1K−1) is obtained at 50% Sn, which is the lowest value among bulk group-IV alloys. The low thermal conductivity achieves high thermoelectric performance and can help to ensure temperature differences within small thermoelectric generators (TEGs) integrated on Si chips, as is the case of Si nanowire TEGs [4]. In contrast to the theoretical studies mentioned above, experimental studies are very limited compared with other group-IV alloys such as silicon germanium and germanium tin. Difficulties of the Si1−x Sn x synthesizing are the extremely low solid solubility of Sn in Si (0.1%), a tenth of that in Ge, and the large (∼20%) mismatch between the Si and α-Sn lattices. Nevertheless, some research groups, including us, showed some possibilities to achieve a high Sn content Si1−x Sn x thin films (x>10%) experimentally; reported the optical properties such as photoluminescence and photo-absorption. However, the technology for freely controlling Sn content is still in its infancy; the Si1−x Sn x ’s thermoelectric properties have not been clarified yet. We will discuss the recent progress on the growth techniques of Si1−x Sn x thin films using solid phase epitaxy/crystallization [5-7], molecular beam epitaxy [8,9], sputtering [10], and the potential in thin-film TEGs application. Acknowledgments This work was partly supported by JSPS KAKENHI (Nos. 19K21971, 20H05188, and 21H01366), PRESTO (No. JPMJPR15R2), and CREST (No. JPMJCR19Q5) from JST, the TEPCO Memorial Foundation, and the Naito Research Grant. References [1] R. A. Soref and C. H. Perry, J. Appl. Phys. 69, 539 (1991). [2] S. N. Khatami and Z. Aksamiji, Phys. Rev. Appl. 6, 014015 (2016). [3] P. D. Maycock, Solid-State Electron. 10, 161 (1967). [4] T. Watanabe et al., 2017 IEEE Electron Devices Technology and Manufacturing Conference, Toyama, Japan, 2017, pp. 86-87. [5] M. Kurosawa et al., Appl. Phys. Lett. 106, 171908 (2015). [6] M. Kurosawa et al., Appl. Phys. Lett. 111, 192106 (2017). [7] M. Kurosawa et al., Jpn. J. Appl. Phys. 58, SAAD02 (2019). [8] R. Yokogawa et al., ECS Trans. 98, 291 (2020). [9] K. Fujimoto et al., Appl. Phys. Express 16, 045501 (2023). [10] T. Oiwa et al., Extended Abstracts of the 2022 International Conference on Solid State Devices and Materials, Makuhari, Japan, 2022, pp. 95-96.

Thermoelectric (TE) energy converters have attracted great interest due to their maintenance-free, long-life, and high-reliability properties. However, improving the output power of TE devices remains a huge challenge. In this work, a high-efficient photo-TE coupling generator based on cuprous iodide (CuI) film is proposed to increase the output power of TE devices. Here, CuI film was prepared by the successive ionic layer adsorption and reaction method. The influence of the photovoltaic (PV) effect on the TE output voltage of CuI film was investigated by an analysis of the experimental results. The results showed that the output voltage of the photo-TE coupling generator had a maximum increment of 83.47% at 343 K compared to the sum of TE and PV voltages. The increase in the output voltage was mainly because of the PV effect rather than the TE effect, while the photo-generated electrons also induce a considerable change in the TE figure of merit. Hence, the strategy proposed in this work might be a potential approach to further improve the output performance of other TE materials.

This paper proposes a concept of battery-assisted battery charger with maximum power point tracking for DC energy transducer such as thermoelectric generator and photo voltaic generator, and shows experimental results to prove the concept. The DC energy transducer is connected in series with a battery to increase the voltage. The plus terminal for the DC energy transducer is connected with the input terminal of a DC-DC buck converter, whereas the battery is connected with the output terminal of the converter. Thus, the current is boosted from the input to the output. When the net current to the battery is positive, the system works as a battery charger. To extract the as much power from the DC energy transducer as possible for high charging efficiency, maximum power point tracking is introduced. The converter was designed in 180 nm 3V CMOS with a silicon area of 1.05 mm2. The concept was experimentally proven by varying the reference voltages to control the input voltage. An all-solid-state battery was charged up from 2.2 V to 2.3 V in two hours by the converter with a flexible thermoelectric generator which had an open-circuit voltage of 0.6 V.

The activation of carbon dioxide (CO2) molecules and separation/transfer of photoinduced charge carriers are two crucial factors influencing the efficiency of CO2 photoreduction. Herein, we report a p-type Bi2Te3/commercial TiO2 (pBT/P25) nanocomposite for enhanced CO2 photoreduction. Upon light irradiation, a temperature gradient formed in pBT induces the Seebeck effect to build a thermoelectric field, which promotes the charge carriers’ separation/transfer. Additionally, pBT with a strong light absorption capacity generates the photothermal effect favoring the activation of CO2 molecules. In addition, the excellent electric conductivity and large work function render pBT an efficient cocatalyst for further improving the charge carriers’ separation/transfer. Owing to the synergistic enhancement effect of pBT on the activation of CO2 molecules and promotion of charge separation/transfer, we achieved the highest CO evolution rate over pBT(2)/P25 of 19.2 μmol·gcat−1·h−1, which was approximately 5.5 times that of bare P25. This work suggests that a thermoelectric material/semiconductor nanocomposite could be developed as an efficient photo-thermo-electro-chemical conversion system for enhanced CO2 reduction via promoting the charge carriers’ separation/transfer.

碩士
國立臺北科技大學
機電整合研究所
98
This study self-develops a novel type of photoelectric conversion modules, adopting pre-prepared dye-sensitized solar cells (DSSCs) and combing with nano-Cu thermoelectric thin film to cover on the sides of the thermoelectric generator (TEG) to absorb outside light to generate electricity and use recycled waste heat to re-generate electricity. And then, the close-loop pulsating heat pipe of filling nano-CuO fluid is prepared on the cooling-side to increase cooling effects and enhance whole power generation efficiency. Thus, this study focuses on the application of elevating efficiency of the thermoelectric modules. For the preparation of the thermoelectric modules, commercial nano-Cu powder is firstly used and the doctor blade is adopted to fabricate nano-Cu heat-transfer film, serving as the media of thermal conductivity and coated on the TEG to promote the output of heat flux and energy. Secondly, submerged arc nanoparticle synthesis system (SNASS) is used to fabricate the nano-CuO fluid and the filling close-loop pulsating heat pipe is applied to the cold side to employ the variation of gas and liquid to increase cooling effects. For the fabrication of photoelectric conversion modules, this study adopts DSSCs with multi-layer TiO2 nano-film to combine with two systems to assemble the photo-thermoelectric modules. For the test of photo-thermoelectric modules, I-V measuring system and heating platform are used to deal with the output effects and electrical storage loop system and nickel-metal hydride batteries are used to test electrical storage time of photo-thermoelectric modules. Finally, the temperature measurement device is employed to analyze the performance output and conversion efficiency of photo-thermoelectric modules by simulated light and practical light. Results shows when the heat source of photo-thermoelectric modules attains 90 ℃, 85.7% power output can be elevated. The temperature difference of cold and hot sides of TEG can reach 7oC shone by simulated light of photo-thermoelectric modules and thermoelectric conversion efficiency can achieve 2.17% and produce 11.32mW/cm2 power output, enhancing 1.4% compared to singly adopting DSSCs.

Heat generation in metallic nanostructure under plasmon is known as plasmonic local heat, and it has been utilized in various applications, for example, cancer therapy, photohermal chemistry, nanowire growth, and so on [1]. G. Baffou et al. reported that Au single nanoparticle generates local heat about 90 K under the light irradiation of 100 mW/cm2 [2]. These facts indicate plasmonic nanostructures will be effective nano-heaters.