Validity of the Mott formula and the origin of thermopower in 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>π</mml:mi></mml:math>
-conjugated semicrystalline polymers

Watanabe, Shun; Ohno, Masahiro; Yamashita, Yu; Terashige, T.; Okamoto, Hiroshi; Takeya, Jun

doi:10.1103/physrevb.100.241201

Cited by 31 publications

(31 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Recently, it has been proved that thermopower is generated from crystalline domains in highly doped polymers, while σ is limited by the localized carriers at the grain boundary. 46 Based on this, we hypothesis that The ESR signal intensity of PCPDTBT-SO 3 K was distinctly increased by H 2 SO 4 treatment, with the increase in integrated area and decrease in full width at half maximum ( Figure 2c).…”

Section: Resultsmentioning

confidence: 75%

A Highly Conductive Conjugated Polyelectrolyte for Flexible Organic Thermoelectrics

Kee

Haque

Lee

et al. 2020

ACS Appl. Energy Mater.

View full text Add to dashboard Cite

Organic thermoelectrics have attracted considerable attention owing to their remarkable advantages, including room-temperature power generation, skin-attachable/wearable applications with biocompatibility, and solution-based high-throughput fabrication. Selfdoped conjugated polyelectrolytes (CPEs) constitute a promising class of conductive organic materials that are considered potential candidates for organic thermoelectrics.

show abstract

Section: Resultsmentioning

confidence: 75%

A Highly Conductive Conjugated Polyelectrolyte for Flexible Organic Thermoelectrics

Kee

Haque

Lee

et al. 2020

ACS Appl. Energy Mater.

View full text Add to dashboard Cite

show abstract

“…Recent work utilized this approach to increase the charge transfer efficiency between the common dopant, F 4 TCNQ, and poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno [3,2-b]thiophene] (PBTTT). [27,28] It was found that F 4 TCNQ dissolved in ionic liquid can increase the doping efficiency of F 4 TCNQ with PBTTT while simultaneously exchanging F 4 TCNQ •− in the film to the counter-ion in the ionic liquid. Since the doping efficiency of F 4 TCNQ was higher when ionic liquid was present, more F 4 TCNQ molecules were ionized which led to more carriers induced in PBTTT.…”

Section: Introductionmentioning

confidence: 99%

Effects of Counter‐Ion Size on Delocalization of Carriers and Stability of Doped Semiconducting Polymers

Thomas

Peterson

Balzer

et al. 2020

Adv Elect Materials

View full text Add to dashboard Cite

Molecular charge transfer dopants either oxidize or reduce the polymeric backbone through accepting or donating an electron. In such cases, the neutralizing counter-ion to the charge carrier on the polymer is the dopant molecule. [1] Protonating the polymer backbone with a Brønsted acid provides a similar effect with the proton donor acting as the counter-ion. [2,3] Electrochemical methods can be used to supply, or remove, electrons if the polymer is supported by a conductive substrate with infiltration of a counter-ion from an electrolyte. [4] These methods effectively tune the electrical conductivity in polymeric semiconductors for emerging applications including bioelectronics [5] and thermoelectrics. [6] For all doping mechanisms, the interactions that exist between a conjugated polymer, a charge carrier, and its corresponding counter-ion are difficult to ascertain. Our lack of understanding stems from a multitude of complications that arise from doping polymers. The morphology of thin films can evolve upon infiltration of dopants, which convolutes the effects of morphology and carrier concentration on the resulting electrical properties. [7] The use of dopants of varying molecular sizes simultaneously changes steric interactions and the energetics of charge transfer, along with the additional possibility of the formation of charge transfer complexes. [8-10] These confounding factors make simple relationships, like how the degree of interaction between the dopant counter-ion and charge carrier impacts the electronic mobility, challenging to determine. A recent formalism to elucidate the importance of interactions between charge carriers and their associated counterions in semiconducting polymers was developed through examining their spectroscopic signatures in the infrared region. The optical properties of polaronic charge carriers in semiconducting polymers are affected by factors such as electronic/vibrational coupling between chains, coulombic interactions, and disorder. [11,12] One model, developed by Spano and coworkers, rationalizes the optical transitions of polaronic carriers in poly(3-hexylthiophene) (P3HT) using a Holstein Hamiltonian modified to incorporate disorder that is present in crystallites of polymers. [13] Both the predicted energies of the optical transitions and their intensities were in good agreement with experimental observations of field-induced charge carriers Since doped polymers require a charge-neutralizing counter-ion to maintain charge neutrality, tailored and high degrees of doping in organic semiconductors requires an understanding of the coupling between ionic and electronic carrier motion. A method of counter-ion exchange is utilized using the polymeric semiconductor poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b] thiophene]-C 14 to deconvolute the effects of ionic/polaronic interactions with the electrical properties of doped semiconducting polymers. In particular, exchanging the counter-ions of the dopant nitrosonium hexafluorophosphate enables investigation into the...

show abstract

“…In principle, PF is related to both α and σ as the magnitude of σ increases as function of n while, in contrast, the magnitude of α decreases with n 11,25 . Fundamentally, studies of thermoelectric properties of semiconducting polymers have been investigated in the context of charge transport mechanisms where researchers have been exploring the correlation between α and σ 25–35 . In 2014, Glaudell et al presented an empirical relation where

α \sim

σ −1/4 by compiling studies of doped thiophene‐based polymers.…”

Section: Introductionmentioning

confidence: 99%

Correlating conductivity and Seebeck coefficient to doping within crystalline and amorphous domains in poly(3‐(methoxyethoxyethoxy)thiophene)

Dong

Onorato

et al. 2021

Journal of Polymer Science

View full text Add to dashboard Cite

Molecular doping of conjugated polymers (CPs) plays a vital role in optimizing organic electronic and energy applications. For the case of organic thermoelectrics, it is commonly believed that doping CPs with a strong dopant could result in higher conductivity (σ) and thus better power factor (PF). Herein, by investigating thermoelectric performance of a polar side‐chain bearing CP, poly(3‐(methoxyethoxyethoxy)thiophene) (P3MEET), vapor doped with fluorinated‐derivative of tetracyanoquinodimethane FnTCNQ (n = 1, 2, 4), we show that using strong dopants can in fact have detrimental effects on the thermoelectric performance of CPs. Despite possessing higher electron affinity, doping P3MEET with F4TCNQ only results in a σ (27.0 S/cm) comparable to samples doped with other two weaker dopants F2TCNQ and F1TCNQ (26.4 and 20.1 S/cm). Interestingly, F4TCNQ‐doped samples display a marked reduction in the Seebeck coefficient (α) compared to F1TCNQ‐ and F2TCNQ‐doped samples from 42 to 13 μV/K, leading to an undesirable suppression of the PF. Structural characterizations coupled with Kang‐Snyder modeling of the α–σ relation show that the reduction of α in F4TCNQ‐doped P3MEET samples originates from the generation of low mobility carrier within P3MEET's amorphous domain. Our results demonstrate that factors such as dopant distribution and doping efficiency within the crystalline and amorphous domains of CPs should play a crucial role in advancing rational design for organic thermoelectrics.

show abstract

Validity of the Mott formula and the origin of thermopower in π -conjugated semicrystalline polymers

Cited by 31 publications

References 38 publications

A Highly Conductive Conjugated Polyelectrolyte for Flexible Organic Thermoelectrics

A Highly Conductive Conjugated Polyelectrolyte for Flexible Organic Thermoelectrics

Effects of Counter‐Ion Size on Delocalization of Carriers and Stability of Doped Semiconducting Polymers

Correlating conductivity and Seebeck coefficient to doping within crystalline and amorphous domains in poly(3‐(methoxyethoxyethoxy)thiophene)

Contact Info

Product

Resources

About