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

TL;DR

This study demonstrates high rectification ratios in donor-acceptor molecular heterojunctions, revealing their potential as molecular diodes with tunable electronic properties at the two-molecule scale.

Contribution

It provides experimental evidence and theoretical analysis of rectification behavior in pentacene-fullerene heterojunctions, highlighting their diode-like characteristics and underlying tunneling mechanisms.

Findings

Rectification ratios >250 at 0.5 V bias and >1000 at 1.2 V bias.

System behaves as a molecular Schottky diode with tunneling transport.

Low-bias rectification ratios vary significantly due to Stark shifts and confinement.

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 fullerene 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 mechanism from semiconducting pentacene to Cu-hybridized metallic fullerene. Low-bias RRs vary by two orders-of-magnitude at the edge of these molecular heterojunctions due to increased Stark shifts and confinement effects.