Science News: 2022 Nature (IF 49.962), N-type Conducting Polymers with Ultrahigh conductivity Achieved by Solution Processing!
Since the pioneering work on doped polyacetylene, conductive polymers (CPs) with high conductivity and solution processability have made great progress, thus opening up a new field of “organic synthetic metals”. A variety of high-performance CPs have been realized, making possible the applications of several organic electronic devices. To achieve highly conductive n-type conducting polymers (n-CPs), both efficient electron transport and high carrier concentration should be obtained. So far, n-CPs with milestone conductivity of 100 S cm-1 have been achieved. However, most high-performance n-CPs have complex chemical structures that require tedious doping procedures involving multiple synthesis steps and oxygen-free condition, limiting the technological transition from research to large-scale commercial production. At present, it is still a challenge to realize a n-CP with thousand-level conductivity and metallic state that are comparable to p-type CPs. This requires a breakthrough in the development of n-CPs.
The researchers published a study in Nature in 2022. Here, the authors propose an easily synthesized highly conductive n-type polymer poly(benzodifurandione) (PBFDO). The reaction combines oxidative polymerization and in situ reductive n-doping, which substantially improves the doping efficiency, reaching nearly 0.9 charges doping level per repeating unit. The results of the study found:
- The resultant polymer exhibits a breakthrough electrical conductivity of over 2,000 S cm-1 with excellent stability and an unexpected solution processability without extra side chains or surfactants.
- Furthermore, detailed investigations of PBFDO revealed coherent charge-transport properties and the existence of metallic state.
This further demonstrates the benchmark performances of electrochemical transistors and thermoelectric generators, thus paving the way for the application of n-type CPs in organic electronics.
The possible mechanisms of combined oxidative polymerization and reductive n-doping for the synthesis of PBFDO. The reaction begins from TMQ-promoted lactone dimerization through a radical pathway, which is followed by oxidative dehydrogenation. Along with the oxidative polymerization proceeding, the formed polymer can be doped with the generated TMQH simultaneously. Doping also makes the doped polymer soluble in DMSO.
The temperature-dependent conductivity and Hall measurement of PBFDO a, Log–log plot of W(T) versus temperature for PBFDO films. The dashed lines show the characteristics of the insulator and metal. b, Conductivity properties at low temperatures. c, Schematic illustration of the Hall measurement. d, Hall resistance VH/I measured at various temperatures ranging from 20 to 323 K. e, Temperature dependence of the conductivity (σ). f, Temperature dependence of the inverse Hall coefficient RH⁻¹ and average carrier concentration assuming ideal Hall effect. g, Temperature dependence of the Hall mobility μH estimated from μH = RHσ.
Py-IR spectra of PBFDO at different temperatures.
Key Word: Conducting polymer, conductivity, organic electronic, doping efficiency
Article link: https://doi.org/10.1038/s41586-022-05295-8