High Efficiency Doping of Conjugated Polymer for Investigation of Intercorrelation of Thermoelectric Effects with Electrical and Morphological Properties

Abstract

Intercorrelation of thermoelectric properties of a doped conjugated semiconducting polymer (PIDF-BT) with charge carrier density, conductive morphology, and crystallinity are systematically investigated. Upon being doped with F4-TCNQ by the sequential doping method, PIDF-BT exhibited a high electrical conductivity over 210 S cm–1. The significant enhancement of electrical conductivity resulted from a high charge carrier density, which is attributed to the effective charge–transfer-based integer doping between PIDF-BT and dopant molecules. Based on the systemic characterization on the optical, electrical, and structural properties of doped PIDF-BT annealed at different temperatures, we investigated the characteristic correlations between thermoelectric properties of PIDF-BT films and their four-probe electrical conductivity, charge carrier density, and charge carrier mobility obtained from AC Hall effect measurements. This study revealed that exercising fine control over the crystallinity and conductive migration of the conjugated polymer films can be a strategic approach to suppressing the degradation of the Seebeck coefficient at high charge carrier density and ultimately to maximizing the power factors of organic thermoelectric devices.

Exploring Wholly Doped Conjugated Polymer Films Based on Hybrid Doping: Strategic Approach for Optimizing Electrical Conductivity and Related Thermoelectric Properties

“…To demonstrate the general applicability of the developed hybrid doping method, we applied the method to a different CP, PIDF-BT (Figure 7a), having a relatively lower degree of crystallinity and in the film and higher degree of CT with F4-TCNQ compared to P3HT. [54,55] It has been reported that sequentially doped PIDF-BT film exhibited a high σ 4P of 240 S cm −1 owing to the efficient dopant (F4-TCNQ) diffusion through the free volume of the amorphous domains (c.f. σ of PIDF-BT film doped by the mixture blending process is 5.0 S cm −1 ).…”

Unraveling Doping Capability of Conjugated Polymers for Strategic Manipulation of Electric Dipole Layer toward Efficient Charge Collection in Perovskite Solar Cells

“…As the degree of diffusion of the doping solution into the polymer matrix is deteriorated significantly because of the tightly inter‐packed chain configuration within the crystalline domain, [ 27 ] sequential doping was conducted with as‐cast films of the CPs without thermal annealing. The CP films were formed from partially nonvolatile o ‐dichlorobenzene (DCB, b.p.…”

“…Compounds 1, 1,2‐bis(5‐(trimethylstannyl)thiophen‐2‐yl)ethene, (3,3′‐difluoro‐[2,2′‐bithiophene]‐5,5′‐diyl)bis(tri‐methylstannane) and 5,5′‐bis(trimethylstannyl)‐2,2′‐bithiazole were prepared according to previously described procedures. [ 27,34–36 ] Detailed chemical structure and synthetic procedures are summarized in Supporting Information, and the molecular weight of obtained CPs was determined by gel permeation chromatography (GPC, Figure S11, Supporting Information).…”

Improvement of Electrical Conductivity in Conjugated Polymers through Cascade Doping with Small‐Molecular Dopants

“…PIDF‐BT containing the IDID moiety has recently been reported to exhibit an outstanding electrical conductivity of >240 S cm −1 upon the implementation of diffusion‐controlled F4TCNQ doping, due to its strong electronic coupling with F4TCNQ. [ 23,24 ] Thus, PIDF‐BT was adopted as a molecular doping platform to quantitatively compare the doping efficiency, and the effectiveness of the devised doping strategy was demonstrated by the cascade doping of F4TCNQ in acetone, followed by NOBF 4 or AuCl 3 treatment in separate acetone and acetonitrile, respectively ( Figure a). After immersing the as‐cast PIDF‐BT film in each dopant solution for 10 s, the current density ( J ) versus electric field ( E ) characteristics were monitored using two‐terminal electrodes to compare the electric response of each doped film under an applied bias (Figure 1b).…”