Effect of mesopore-induced strain/stress on the thermoelectric properties of mesoporous ZnO thin films

Hong, Min Hee; Shim, Dong Il; Cho, Hyung Hee; Park, Hyung Ho

doi:10.1016/j.apsusc.2018.01.283

Cited by 10 publications

(7 citation statements)

References 26 publications

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“…Recent work has focused on a multiscale disorder to reduce the phonon contribution to thermal conductivity while maintaining electrical conductivity . Thin-film thermoelectrics allow great control over disorder using strain, grain boundary control, and local doping techniques. − The advantage of thin-film thermoelectrics is that they can handle higher heat fluxes compared to the bulk due to their lower thermal resistance, but a downside is that a lower temperature difference (Δ T ) can be sustained across them. Ultimately, to improve microcooler performance, one must optimize both the material properties and the electrical interfaces with the contacts.…”

Section: Introductionmentioning

confidence: 99%

Electrodeposited Thin-Film Micro-Thermoelectric Coolers with Extreme Heat Flux Handling and Microsecond Time Response

Corbett

Gautam

Lal

et al. 2021

ACS Appl. Mater. Interfaces

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Thin-film thermoelectric coolers are emerging as a viable option for the on-chip temperature management of electronic and photonic integrated circuits. In this work, we demonstrate the record heat flux handling capability of electrodeposited Bi 2 Te 3 films of 720(±60) W cm −2 at room temperature, achieved by careful control of the contact interfaces to reduce contact resistance. The characteristic parameters of a single leg thin-film devices were measured in situ, giving a Seebeck coefficient of S = −121(±6) μV K −1 , thermal conductivity of κ = 0.85(±0.08) W m −1 K −1 , electrical conductivity of σ = 5.2(±0.32) × 10 4 S m −1 , and electrical contact resistivity of ∼10 −11 Ω m 2 . These thermoelectric parameters lead to a material ZT = 0.26(±0.04), which, for our device structure, allowed a net cooling of ΔT max = 4.4(±0.12) K. A response time of τ = 20 μs was measured experimentally. This work shows that with the correct treatment of contact interfaces, electrodeposited thin-film thermoelectrics can compete with more complicated and expensive technologies such as metal organic chemical vapor deposition (MOCVD) multilayers.

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Section: Introductionmentioning

confidence: 99%

Electrodeposited Thin-Film Micro-Thermoelectric Coolers with Extreme Heat Flux Handling and Microsecond Time Response

Corbett

Gautam

Lal

et al. 2021

ACS Appl. Mater. Interfaces

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“…(A)Temperature‐dependent PF values of GZO thin films in this work; (B) the highest PF value comparison at higher (left side) and lower (right side) temperatures for GZO thin film in this work and other ZnO‐based thin films from references (AO/ZnO is Al 2 O 3 /ZnO superlattices and ZTO stands for Sn doped ZnO films) 10,29‐32 [Color figure can be viewed at wileyonlinelibrary.com]…”

Section: Resultsmentioning

confidence: 97%

“…Consequently, with excellent electrical conductivity originated from higher carrier concentration and Seebeck coefficient due to large DOS effective mass, GZO-3 nm ZnO-GZO-V thin film presents better power factor values over the entire temperature range with the highest value of 434 μW m −1 K −2 at 623 K, as shown in Figure 7A. Compared with other ZnO-based thin films taken from the references 10,[29][30][31][32] (Figure 7B), the PF value of our GZO-ZnO-GZO-V thin film is still the highest and competitive not only at higher temperatures but also at room temperature. As a result, sandwich structure design combined with defect engineering is an effective approach to realize simultaneous increase of the Seebeck coefficient and electrical conductivity and thus further improve the thermoelectric performance for ZnO-based thin films.…”

mentioning

confidence: 96%

A sandwich structure assisted by defect engineering for higher thermoelectric performance in ZnO‐based films

Zhou

Zou

et al. 2020

J. Am. Ceram. Soc.

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Gallium (Ga) doping together with low dimensionality has been a promising approach to improve thermoelectric performance of zinc oxide (ZnO) materials, due to the increase of carrier concentration and suppression of phonon transport. So far, the highest power factor of Ga-doped ZnO (GZO) thin films has reached 280 μW m −1 K −2 , which is still limited for practical applications. In this work, we have simultaneously optimized the electrical conductivity and Seebeck coefficient of GZO thin films using the combination of oxygen defects and sandwich structure (GZO-ZnO-GZO). Benefiting from energy filtering effect at the interface between GZO and ZnO layers and high oxygen vacancy concentration, the density of states (DOS) effective mass has been increased together with a relatively high carrier concentration. As a result, an improved power factor value of 434 μW m −1 K −2 at 623 K has been achieved, which is comparable to the best values reported for ZnO-based films. This method of combining defect engineering and sandwich structure design shows great potential in enhancing the thermoelectric performance of ZnO-based thin films or other oxide materials. K E Y W O R D S defect engineering, electrical conductivity, energy filtering effects, GZO thin film, sandwich structure design How to cite this article: Zhou Z, Xu Y, Zou M, et al. A sandwich structure assisted by defect engineering for higher thermoelectric performance in ZnO-based films.

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“…56 In the presintering process, the low-temperature increase rate helps to stabilize the films, thereby decreasing the collapse of the ZnO films. 27 However, under UV irradiation, photooxidative degradation directly occurs, which results in breaking of the polymer chains into free radicals and small molecules. 57 Therefore, a more serious collapse and smaller pore sizes are observed in the final UV-irradiated ZnO films.…”

Section: Resultsmentioning

confidence: 99%

“…However, as far as we know, rare effort has been made to study the influence of different post-treatment techniques on the pore size of the final polymer-free inorganic films. In the literature, the strain changes of mesoporous ZnO structures after organic surfactant decomposition via ultraviolet (UV) irradiation and thermal annealing were compared to accurately calculate the strain change in the ZnO crystallization process . In general, UV irradiation and high-temperature sintering are two commonly used methods for the diblock copolymer removal from polymer–metal oxide composite films prepared via sol–gel synthesis. ,,− During UV irradiation or sintering, the polymer template is removed.…”

Section: Introductionmentioning

confidence: 99%

Comparison of UV Irradiation and Sintering on Mesoporous Spongelike ZnO Films Prepared from PS-b-P4VP Templated Sol–Gel Synthesis

Xia

Cao

Hohn

et al. 2018

ACS Appl. Nano Mater.

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Mesoporous ZnO films with large surface-area-to-volume ratio show great promise in multiple applications, among which solid-state dye-sensitized solar cells (ssDSSCs) have attracted great attention in the field of photovoltaics. An appropriate mesopore size in the nanostructured ZnO films significantly plays an indispensable role in improving the device efficiency that resulted from an efficient penetration of dye molecules and solid hole transport material. In the present work, mesoporous spongelike ZnO films are prepared using sol–gel synthesis templated by a diblock copolymer polystyrene-block-poly(4-vinylpyridine). Two different template removal techniques, ultraviolet (UV) irradiation and high-temperature sintering, are used to compare their respective impact on the pore sizes of the final ZnO thin films. Both the surface morphology and the inner morphology show that mesopores obtained via UV irradiation are smaller as compared to their sintered counterparts. Moreover, increasing the template-to-ZnO precursor ratio is found to further enlarge present mesopores. Accordingly, a strong correlation between the pore sizes of sol–gel synthesized ZnO films and photovoltaic performance of fabricated ssDSSCs is demonstrated. In contrast with the devices fabricated from the UV-irradiated ZnO films, those obtained from sintered samples show >2 times higher efficiency.

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Effect of mesopore-induced strain/stress on the thermoelectric properties of mesoporous ZnO thin films

Cited by 10 publications

References 26 publications

Electrodeposited Thin-Film Micro-Thermoelectric Coolers with Extreme Heat Flux Handling and Microsecond Time Response

Electrodeposited Thin-Film Micro-Thermoelectric Coolers with Extreme Heat Flux Handling and Microsecond Time Response

A sandwich structure assisted by defect engineering for higher thermoelectric performance in ZnO‐based films

Comparison of UV Irradiation and Sintering on Mesoporous Spongelike ZnO Films Prepared from PS-b-P4VP Templated Sol–Gel Synthesis

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