Morphology controls the thermoelectric power factor of a doped semiconducting polymer

Patel, Shrayesh N.; Glaudell, Anne M.; Peterson, Kelly A.; Thomas, Elayne M.; O’Hara, Kathryn; Lim, Eunhee; Chabinyc, Michael L.

doi:10.1126/sciadv.1700434

Cited by 301 publications

(422 citation statements)

References 71 publications

(142 reference statements)

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“…[50] A general theoretical frame relating to the S = f(σ) scaling law was recently proposed by these authors. [51,52] The set of (S, σ) data obtained over a large range of conductivities (1.0-10 5 S cm −1 ) in this study helps further probe the S = f(σ) correlations and its anisotropy especially in a regime of high conductivities (σ > 10 3 S cm −1 ). [50] In PEDOT:TOS, the S-σ curve is well fitted with s = 1 pointing at a transport mechanism dominated by acoustic phonon scattering.…”

Section: Correlations Between Thermopower and Charge Conductivity In mentioning

confidence: 74%

Bringing Conducting Polymers to High Order: Toward Conductivities beyond 10⁵ S cm⁻¹ and Thermoelectric Power Factors of 2 mW m⁻¹ K⁻²

Vijayakumar

Zhong

Untilova

et al. 2019

Advanced Energy Materials

163

181

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Here, an effective design strategy of polymer thermoelectric materials based on structural control in doped polymer semiconductors is presented. The strategy is illustrated for two archetypical polythiophenes, e.g., poly(2,5‐bis(3‐dodecyl‐2‐thienyl)thieno[3,2‐b]thiophene) (C12‐PBTTT) and regioregular poly(3‐hexylthiophene) (P3HT). FeCl3 doping of aligned films results in charge conductivities up to 2 × 105 S cm−1 and metallic‐like thermopowers similar to iodine‐doped polyacetylene. The films are almost optically transparent and show strongly polarized near‐infrared polaronic bands (dichroic ratio >10). The comparative study of structure–property correlations in P3HT and C12‐PBTTT identifies three conditions to obtain conductivities beyond 105 S cm−1: i) achieve high in‐plane orientation of conjugated polymers with high persistence length; ii) ensure uniform chain oxidation of the polymer backbones by regular intercalation of dopant molecules in the polymer structure without disrupting alignment of π‐stacked layers; and iii) maintain a percolating nanomorphology along the chain direction. The highly anisotropic conducting polymer films are ideal model systems to investigate the correlations between thermopower S and charge conductivity σ. A scaling law S ∝ σ−1/4 prevails along the chain direction, but a different S ∝ −ln(σ) relation is observed perpendicular to the chains, suggesting different charge transport mechanisms. The simultaneous increase of charge conductivity and thermopower along the chain direction results in a substantial improvement of thermoelectric power factors up to 2 mW m−1 K−2 in C12‐PBTTT.

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Section: Correlations Between Thermopower and Charge Conductivity In mentioning

confidence: 74%

Bringing Conducting Polymers to High Order: Toward Conductivities beyond 10⁵ S cm⁻¹ and Thermoelectric Power Factors of 2 mW m⁻¹ K⁻²

Vijayakumar

Zhong

Untilova

et al. 2019

Advanced Energy Materials

163

181

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“…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.…”

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

confidence: 99%

“…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%

“…[14] We therefore attribute the increased conductivity, and virtually unaltered thermopower, of the inverse-sequentially doped samples to a better morphology that effectively leads to faster transport while the energetics, which determine the thermopower, are largely unaffected. [6,17] In terms of the simple model that is discussed below, the effect of the improved morphology would be mapped on the (increased) attempt to hop frequency, which increases conductivity while leaving the thermopower unaffected. The mentioned values combine into a maximum PF ≈ 35 µW m −1 K −2 (average PF, 30 ± 5 µW m −1 K −2 ), which is among the highest n-type power factor that has been reported for solution-processed OTE.…”

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

confidence: 99%

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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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“…Figure 2ab shows the absorption spectra for films of several (semi-) conducting polymers and carbon nanotubes, respectively. [21] PEDOT:PSS in comparison absorbs weakly in the UV-vis range but absorbs NIR radiation strongly due to a Drude tail of free carriers. [25] In contrast, a film of PBTTT vapor-doped with F 4 TCNQ shows broad absorption across the UV-vis regions and even reaching up to 1000 nm in the NIR region.…”

Section: Solar Absorber Characterizationmentioning

confidence: 99%

Solar Harvesting: a Unique Opportunity for Organic Thermoelectrics?

Jurado

Dörling

Zapata‐Arteaga

et al. 2019

Advanced Energy Materials

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Thermoelectrics have emerged as a strategy for solar‐to‐electricity conversion, as they can complement photovoltaic devices as IR harvesters or operate as stand‐alone systems often under strong light and heat concentration. Inspired by the recent success of inorganic‐based solar thermoelectric generators (STEGs), in this manuscript, the potential of benchmark organic thermoelectric materials for solar harvesting is evaluated. It is shown that the inherent properties of organic semiconductors allow the possibility of fabricating organic STEGs (SOTEGs) of extraordinary simplicity. The broadband light absorption exhibited by most organic thermoelectrics combined with their low thermal conductivities results in a significant temperature rise upon illumination as seen by IR thermography. Under 2 sun illumination, a temperature difference of 50 K establishes between the illuminated and the non‐illuminated sides of a poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) film, and ≈40 K for a carbon nanotube/cellulose composite. Moreover, when using light as a heat source, the Seebeck coefficient remains unaffected, while a small photoconductivity effect is observed in PEDOT:PSS and carbon nanotubes. Then, the effect of several geometrical factors on the power output of a solar organic thermoelectric generator is investigated, enabling us to propose simple SOTEG geometries that capitalize on the planar geometry typical of solution‐processable materials. Finally, a proof‐of‐concept SOTEG is demonstrated, generating 180 nW under 2 suns.

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Morphology controls the thermoelectric power factor of a doped semiconducting polymer

Abstract: The orientational correlation length of domains in a semiconducting polymer controls its thermoelectric performance.

Cited by 301 publications

References 71 publications

Bringing Conducting Polymers to High Order: Toward Conductivities beyond 10⁵ S cm⁻¹ and Thermoelectric Power Factors of 2 mW m⁻¹ K⁻²

Bringing Conducting Polymers to High Order: Toward Conductivities beyond 10⁵ S cm⁻¹ and Thermoelectric Power Factors of 2 mW m⁻¹ K⁻²

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

Solar Harvesting: a Unique Opportunity for Organic Thermoelectrics?

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Morphology controls the thermoelectric power factor of a doped semiconducting polymer

Abstract: The orientational correlation length of domains in a semiconducting polymer controls its thermoelectric performance.

Cited by 301 publications

References 71 publications

Bringing Conducting Polymers to High Order: Toward Conductivities beyond 105 S cm−1 and Thermoelectric Power Factors of 2 mW m−1 K−2

Bringing Conducting Polymers to High Order: Toward Conductivities beyond 105 S cm−1 and Thermoelectric Power Factors of 2 mW m−1 K−2

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

Solar Harvesting: a Unique Opportunity for Organic Thermoelectrics?

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Bringing Conducting Polymers to High Order: Toward Conductivities beyond 10⁵ S cm⁻¹ and Thermoelectric Power Factors of 2 mW m⁻¹ K⁻²

Bringing Conducting Polymers to High Order: Toward Conductivities beyond 10⁵ S cm⁻¹ and Thermoelectric Power Factors of 2 mW m⁻¹ K⁻²