Intermolecular electron‐transfer reactions are key processes in physics, chemistry, and biology. The electron‐transfer rates depend primarily on the system reorganization energy, that is, the energetic cost to rearrange each reactant and its surrounding environment when a charge is transferred. Despite the evident impact of electron‐transfer reactions on charge‐carrier hopping, well‐controlled electronic transport measurements using monolithically integrated electrochemical devices have not successfully measured the reorganization energies to this date. Here, it is shown that self‐rolling nanomembrane devices with strain‐engineered mechanical properties, on‐a‐chip monolithic integration, and multi‐environment operation features can overcome this challenge. The ongoing advances in nanomembrane‐origami technology allow to manufacture the nCap, a nanocapacitor platform, to perform molecular‐level charge transport characterization. Thereby, employing nCap, the copper‐phthalocyanine (CuPc) reorganization energy is probed, ≈0.93 eV, from temperature‐dependent measurements of CuPc nanometer‐thick films. Supporting the experimental findings, density functional theory calculations provide the atomistic picture of the measured CuPc charge‐transfer reaction. The experimental strategy demonstrated here is a consistent route towards determining the reorganization energy of a system formed by molecules monolithically integrated into electrochemical nanodevices.

The bottom-up engineering of organic/inorganic hybrids is a crucial step toward advanced nanomaterial technologies. Understanding the energy level alignment at hybrid interfaces provides a valuable comprehension of the systems′ electronic properties -which are decisive for well-designed device applications. Here, active interfaces of ultrathin (≈10 nm) molecular rectifying diodes that are capable of achieving a 4-order-magnitude rectification ratio along with 10 MHz cutoff frequency, both in a single nanodevice, are engineered. Atomic force microscopy and Kelvin-Probe analysis are employed to investigate the surface potential of the hybrid devices′ organic/inorganic interfaces, which comprise a metal (M) electrode in contact with a fewnanometer-thick copper phthalocyanine (CuPc) film. Thereby a nanometerresolved quantification of the CuPc film work functions as well as the M/ CuPc diode's space-charge densities are delivered. By recognizing that the molecular rectifying diode is a functional building block for nanoscale electronics, the findings address crucial advances to the design of high-performance molecular rectifiers based on organic/inorganic interface engineering.