3,4,5‐Trimethoxy Substitution on an N‐DMBI Dopant with New N‐Type Polymers: Polymer‐Dopant Matching for Improved Conductivity‐Seebeck Coefficient Relationship

Abstract

Achieving high electrical conductivity and thermoelectric power factor simultaneously for n-type organic thermoelectrics is still challenging. By constructing two new acceptor-acceptor n-type conjugated polymers with different backbones and introducing the 3,4,5-trimethoxyphenyl group to form the new n-type dopant 1,(TP-DMBI), high electrical conductivity of 11 S cm À1 and power factor of 32 mW m À1 K À2 are achieved. Calculations using Density Functional Theory show that TP-DMBI presents a higher singly occupied molecular orbital (SOMO) energy level of À1.94 eV than that of the common dopant 4-(1, 3dimethyl-2, 3-dihydro-1H-benzoimidazol-2-yl) phenyl) dimethylamine (N-DMBI) (À2.36 eV), which can result in a larger offset between the SOMO of dopant and lowest unoccupied molecular orbital (LUMO) of n-type polymers, though that effect may not be dominant in the present work. The doped polymer films exhibit higher Seebeck coefficient and power factor than films using N-DMBI at the same doping levels or similar electrical conductivity levels. Moreover, TP-DMBI doped polymer films offer much higher electron mobility of up to 0.53 cm 2 V À1 s À1 than films with N-DMBI doping, demonstrating the potential of TP-DMBI, and 3,4,5-trialkoxy DMBIs more broadly, for high performance n-type organic thermoelectrics.

Pyrazinacene conjugated polymers: a breakthrough in synthesis and unraveling the conjugation continuum

“…These pyrazinacene polymers hold great promise across a wide range of applications, including organic electronics, energy conversion and storage, electrochemical transistors, catalysis, and sensors. [68][69][70][71][72][73][74][75] Additionally, they help to narrow the gap between number of p-type and n-type polymers.…”

Thermoelectric Properties of Spray Coated n-Type PEDOT:PSS Film

“…However, inorganic TE materials have some significant drawbacks, including high production costs, high heat loss, fragility, and possible toxicity from heavy metals [4]. Organic conducting polymers e.g., PEDOT:PSS present a promising platform as an alternative because of their great mechanical flexibility, high stretchability, ease of solution processing, and environmental friendliness [5]. Because of these benefits, using organic conducting polymers in scale TE generators is now technically and financially possible.…”

Molecular Descriptor and Criterion for Efficient N-Doping of Organic Semiconductors

“…Nevertheless, its dehydrogenated neutral radical N-DMBI• is very reductive; the singly occupied molecular orbital (SOMO) level is calculated to be ca. ~ -2.4 eV 34,[41][42][43] or ~ -2.8 eV, 28,44 depending on the method. Therefore, the C-H bond activation process to form N-DMBI• that can reduce OSCs was first proposed, 33 and it was supported by the primary kinetic isotope effect (KIE) experiment.…”