Large spatially-resolved rectification in a donor-acceptor molecular heterojunction

Abstract

We demonstrate that rectification ratios (RR) of <250 (<1000) at biases of 0.5 V (1.2 V) are achievable at the two-molecule limit for donor-acceptor bilayers of pentacene on C60 on Cu using scanning tunneling spectroscopy and microscopy. Using first-principles calculations, we show that the system behaves as a molecular Schottky diode, with a tunneling transport mech- anism from semiconducting pentacene to Cu-hybridized metallic C60. Low-bias RR’s vary by two orders-of-magnitude at the edge of these molecular heterojunctions due to increased Stark shifts and confinement effects.