Electron transport in organic matter

Natural carbonaceous materials (NCMs) have recently emerged as promising organic semiconducting materials for electronics and catalysis, although the fundamental picture of charge transport within NCM systems is still incomplete. Morphologically, NCMs exhibit reminiscence of disordered organic solids, yet the experimental measurements demonstrate a transport regime that surprisingly follows Mott’s formula derived for variable-range hopping in inorganic noncrystalline materials. With ab initio and kinetic Monte Carlo simulations, a temperature scaling is revealed between the Gaussian-defect model log(σ) ∼ T^−2 typical for organic matter and the Mott-like log(σ) ∼ T^−1/4 for a wide spectrum of intermolecular connectivity. As dominant transport descriptors, energy levels and coupling strengths are screened among 30 small molecules with varying sizes, shapes, sp2 /sp3 ratios, side chains, and functional groups. These analyses provide insight for the design of NCM electronics, and should also be applicable to disordered molecular materials in general.

• Charge Transport in Highly Heterogeneous Natural Carbonaceous Materials (Advanced Functional Materials, 2019)