Remarkable conductivity enhancement in P-doped polythiophenes via rational engineering of polymer-dopant interactions

High‐Performance and Ecofriendly Organic Thermoelectrics Enabled by N‐Type Polythiophene Derivatives with Doping‐Induced Molecular Order

“…The resulting polymer-dopant-polymer supramolecular systems with ultra-tight packing allow for fast charge transfer in a higher doping load, resulting in remarkable enhancements in charge carrier mobility and electrical conductivity. [30] In brief, there are three possible pathways in which doping enhances the molecular packing: i) After doping, the ground state polythiophene is transformed into the charged state, accompanied by the introduction of dopant counterions, both of which affect molecular stacking. [28b] ii) Straightening of alkyl side chains when dopants enter the side chains region, which increases the lamellar spacing but can additionally allow the polymer backbones to be stacked more tightly in the 𝜋-𝜋 stacking direction.…”

Interplay between Side Chain Density and Polymer Alignment: Two Competing Strategies for Enhancing the Thermoelectric Performance of P3HT Analogues

“…A recent study by Kim et al has also observed the same trend upon doping a similar copolymer system with F4TCNQ. Albeit at lower electrical conductivity, they observed an increase in electrical conductivity of thin films with more thiophene co-monomer when doping via blending in solution …”

“…Albeit at lower electrical conductivity, they observed an increase in electrical conductivity of thin films with more thiophene co-monomer when doping via blending in solution. 25 As a simple synthetic tool, we thus find that introducing side chain vacancies does not, perhaps somewhat contrary to simplistic consideration regarding the extra free volume, allow for higher charge carrier concentrations during doping. On the other hand, the introduction of side chain vacancies makes the T19 and T24 copolymers more facile to structural reorganization upon doping.…”

“…The positions of the units with and without side chains are randomly distributed in the polymer chain. The effect of randomly altering the side chain density in polythiophenes is well documented to improve the charge carrier mobility; however, the effect on the thermoelectric properties is not so established. − For the non-aligned films, the electrical conductivity after doping with F4TCNQ increased gradually with the decreasing side chain density, affording a sixfold increase for the highest thiophene content ( x = 24) compared to P3HT. On the other hand, polymer alignment by high-temperature rubbing proved less efficient with decreasing side chain density .…”

A Highly Conductive n-Type Polythiophene Derivative: Effect of Molecular Weight on n-Doping Behavior and Thermoelectric Performance

“…Moreover, for a given target charge carrier density, the poor miscibility largely increases the amount of the incorporated dopant molecules, which tends to destroy the microstructure and morphology of the film, thereby reducing the carrier mobility and conductivity of n-doped polymers. , To improve miscibility between the host polymers and dopants, the common design strategies are to introduce twisted polymer backbone or polar side chains. − However, these strategies often have an adverse effect on the molecular stacking of conjugated polymers in the solid state and, thus, reduce the carrier mobility. , For example, Fabiano et al reported that doping distorts the D–A copolymer backbone, and this distorted backbone structure affects the polaron delocalization length and activation energy for charge transport, resulting in higher activation energy of polaron generation for the structurally disordered D–A copolymer . Recently, several strategies have been reported to enhance the dopant tolerance of p-type polymers. , However, at present, there are few methods that can simultaneously improve the carrier mobility, doping level, and dopant tolerance/miscibility of n-type conjugated polymers.…”