Organic Thermoelectric Materials: Emerging Green Energy Materials Converting Heat to Electricity Directly and Efficiently

Zhang, Qian; Sun, Yimeng; Xu, Wei; Zhu, Daoben

doi:10.1002/adma.201305371

Cited by 809 publications

(627 citation statements)

References 161 publications

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“…Recently, a lot of work has been reported on p-type thermoelectric organic semiconductors (OSCs), [2][3][4][5][6] for example, achieving a highest power factor PF over 300 µW m −1 K −2 with a thermoelectric figure of merit ZT ≈ 0.25 based on PEDOT derivatives. [5] Compared to p-type OTE, the development of n-type thermoelectric materials is lagging behind, which can www.advelectronicmat.de n-type OTE by studying the most common n-type OSC, PCBM, doped with an N-DBI derivative.…”

Section: High Seebeck Coefficient and Power Factor In N-type Organic mentioning

confidence: 99%

High Seebeck Coefficient and Power Factor in n‐Type Organic Thermoelectrics

Zuo

Wang

et al. 2017

Adv Elect Materials

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be attributed to the absence of an n-type equivalent of PEDOT, the overall scarcity of n-type OSCs, and the inefficiency of most n-type dopants. Since most good OSCs that are used as n-type materials like [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) and N2200 have a lowest unoccupied molecular orbital (LUMO) around −4.0 eV, [7,8] it is very difficult to realize a stable dopant with a HOMO above −4.0 eV as would be required for efficient electron transfer. Fortunately, Wei et al. have reported a promising material, (4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl) dimethylamine (N-DMBI), that can be used as stable n-type dopant due to a two-step thermally activated doping mechanism. [9] Very recently, Huang et al. used this dopant to achieve record values for PF = 105 µW m −1 K −2 and ZT = 0.11 at room temperature for the small molecule A-DCV-DPPTT. [10] Some reports also have demonstrated that dihydro-1H-benzoimidazol-2-yl (N-DBI) derivatives can improve the electrical conductivity by several orders of magnitude in n-type OTE by solution-processing. For example, Schlitz et al. have shown that solution mixtures of P(NDIOD-T2) with 9 mol% N-DBI derivatives can achieve σ ≈ 1 S m −1 and a PF over 0.6 µW m −1 K −2 . [11] Yuan et al. reported a small-molecule 2DQTT-o-OD that, with 10 wt% of a novel N-DBI derivative incorporated in solution, acquires a PF of 17.2 µW m −1 K −2 at room temperature. [12] Shi et al. achieved a high electron mobility in FBDPPV with σ ≈ 1400 S m −1 and PF ≈ 28 µW m −1 K −2 , when adding around 5 wt% N-DMBI in solution. [13] Despite the positive effect of N-DMBI and N-DBI derivatives on electrical conductivity, it probably fails to further increase σ and PF upon further increasing the volume fraction in solution mixtures due to degradation of the blend morphology. [14] Liu et al. demonstrated a modified fullerene derivative, PTEG-1, that shows an increased miscibility at the nanoscale level and thereby achieved a PF of 16.7 µW m −1 K −2 with σ ≈ 205 S m −1 at 40 mol% of N-DMBI. [15] For p-type OTE, most reported experimental data seem to follow an empirical quasi-universal power law relationship between the Seebeck coefficient S and conductivity as S ∝ σ − 1/4 . [2,3] In view of the limited number of reported data, it is still unclear whether n-type OTE also follow this power law, and different power law slopes have been reported. [15,16] Here, we introduce a novel, inverse-sequential doping procedure that mitigates the need for solvent orthogonality in conventional sequential doping to investigate the potential of deposited on a previously cast dopant 4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)-N,N-diphenylaniline film to achieve a very high power factor PF ≈ 35 µW m −1 K −2 with a conductivity σ ≈ 40 S m −1 is introduced. It is also shown that n-type organic semiconductors obey the −1/4 power law relation between Seebeck coefficient S and σ that are previously found for p-type materials. An analytical model on basis of variable range hopping unifies these results. Th...

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Section: High Seebeck Coefficient and Power Factor In N-type Organic mentioning

confidence: 99%

High Seebeck Coefficient and Power Factor in n‐Type Organic Thermoelectrics

Zuo

Wang

et al. 2017

Adv Elect Materials

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“…Besides, organic materials usually have lower thermal conductivity, can be easier produced, are cost effective and are environmentally friendly. In the past two decades big efforts were undertaken to investigate the thermoelectric applications of organic materials, especially of conducting polymers (see the review [1]). …”

Section: Introductionmentioning

confidence: 99%

Thermoelectric Properties of Nanostructured Tetrathiotetracene Iodide Crystals: 3D Modeling

Casian

Sanduleac

2015

Materials Today: Proceedings

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A more complete three-dimensional (3D) physical model for nanostructured crystals of tetrathiotetracene iodide, TTT 2 I 3 , is presented. The restrictions on the thermoelectric figure of merit ZT that this model involves are determined. At the same time, the criteria of application of simplified 1D model are defined more precisely. In TTT 2 I 3 crystals the carriers are holes. As earlier, two interaction mechanisms of holes with acoustic phonons are considered, generalized for 3D case. One interaction is similar to that of polaron and other to that of deformation potential. Interaction of carriers with impurities and defects is also taken into account. Along chains (x direction) the transport mechanism is of the band type, but in the transversal directions it is of hopping type. The electrical conductivity σ xx , the thermopower (Seebeck coefficient) S xx , the electronic thermal conductivity e xx  and (ZT) xx along the conductive chains have been modelled for the first time in the 3D model. Optimal parameters which predict a considerable increase of (ZT) xx are determined.

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“…C In recent years, use of organic semiconductors for heat-to-electricity conversion at relatively low temperatures has attracted considerable attention. [1][2][3][4][5][6] Compared with their inorganic counterparts, organic semiconductors benefit from the possibility of large-area device fabrication, low energy consumption during device fabrication, low capital costs, and design flexibility. To accurately evaluate candidate thermoelectric materials, the so-called Seebeck coefficient (voltage difference divided by a corresponding temperature difference), electrical conductivity, and thermal conductivity are the most important parameters that need to be scrutinized.…”

mentioning

confidence: 99%

Measurement of in-plane thermal conductivity in polymer films

et al. 2016

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Measuring the in-plane thermal conductivity of organic thermoelectric materials is challenging but is critically important. Here, a method to study the in-plane thermal conductivity of free-standing films (via the use of commercial equipment) based on temperature wave analysis is explored in depth. This subject method required a free-standing thin film with a thickness larger than 10 μm and an area larger than 1 cm2, which are not difficult to obtain for most solution-processable organic thermoelectric materials. We evaluated thermal conductivities and anisotropic ratios for various types of samples including insulating polymers, undoped semiconducting polymers, doped conducting polymers, and one-dimensional carbon fiber bulky papers. This approach facilitated a rapid screening of in-plane thermal conductivities for various organic thermoelectric materials.

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Organic Thermoelectric Materials: Emerging Green Energy Materials Converting Heat to Electricity Directly and Efficiently

Cited by 809 publications

References 161 publications

High Seebeck Coefficient and Power Factor in n‐Type Organic Thermoelectrics

High Seebeck Coefficient and Power Factor in n‐Type Organic Thermoelectrics

Thermoelectric Properties of Nanostructured Tetrathiotetracene Iodide Crystals: 3D Modeling

Measurement of in-plane thermal conductivity in polymer films

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