Tunable two-dimensional interfacial coupling in molecular heterostructures

Two-dimensional van der Waals heterostructures are of considerable interest for the next generation nanoelectronics because of their unique interlayer coupling and optoelectronic properties. Here, we report a modified Langmuir-Blodgett method to organize twodimensional molecular charge transfer crystals into arbitrarily and vertically stacked heterostructures, consisting of bis(ethylenedithio) tetrathiafulvalene (BEDT-TTF)/C-60 and poly (3-dodecylthiophene-2,5-diyl) (P3DDT)/C-60 nanosheets. A strong and anisotropic interfacial coupling between the charge transfer pairs is demonstrated. The van der Waals heterostructures exhibit pressure dependent sensitivity with a high piezoresistance coefficient of -4.4 x 10(-6) Pa-1, and conductance and capacitance tunable by external stimuli (ferroelectric field and magnetic field). Density functional theory calculations confirm charge transfer between the n-orbitals of the S atoms in BEDT-TTF of the BEDT-TTF/C-60 layer and the pi* orbitals of C atoms in C-60 of the P3DDT/C-60 layer contribute to the inter-complex CT. The two-dimensional molecular van der Waals heterostructures with tunable optical-electronic-magnetic coupling properties are promising for flexible electronic applications.