Charge carrier transport properties of porous carbon nanostructure with covalent organic frameworks

Carbon-framework-based nanostructures (CFBNs) with atomically precise well-tailored carbon-vacancy defect structures hold significant potentials for application in optoelectronic devices and catalysis materials. However, a major challenge for the practical application of these materials is their notable low conductivity. In this study, we conducted terahertz time-domain spectroscopy (THz-TDS) measurements and first-principles calculations to investigate the transport properties of CFBNs with different carbon-vacancy defect structures or porous configurations. Our THz-TDS measurements reveal that high carrier densities exist in CFBNs we studied and show that electron scattering at disordered lattices domains and defect or porous edges significantly reduces carrier mobility. Despite the observed high carrier densities, our first-principles calculations revealed a semiconducting band structure for pristine CFBNs and deep transition energy level for native defects. By combining these calculated results with the measured conductivity and carrier density, we propose that the high carrier density observed in CFBN samples is the result of thermally excited charge carriers in localized states, while the low conductivity is contributed by carrier hopping in localized states and extreme scattering in extended states. Both of these phenomena are induced by the disordered lattices in CFBNs. Our findings provide insights into the transport properties of CFBNs, which are essential for the advancement of high-performance carbon-based devices.