Nanoscale probing of charge transport in an organic field-effect transistor at cryogenic temperatures

Abstract

We studied charge transport in a field-effect transistor based on an anthracene crystal by single-molecule spectroscopy at cryogenic temperatures. When applying a control voltage to the gate, source and drain electrodes, we observe spectral drifts of the probe molecules' lines, which follow strongly non-exponential (stretched) kinetics, from seconds to tens of minutes. Applying a gate voltage alone, we find a dependence of the spectral shift as the logarithm of time. When an additional source-drain voltage is applied, the spectral shift follows a power law of time, similar to the elementary step of conduction in amorphous solids, postulated in the continuous-time random walk theory of Scher and Montroll.

Single-molecule photophysics, from cryogenic to ambient conditions

“…Experimental studies of these kinetics were limited to times longer than a fraction of a second by the spectral scanning rate of the laser, and shorter than several hours by the available liquid helium supply. 102 These slow processes are attributed to trapping and detrapping of injected charges, which (at cryogenic temperatures) occur through widely distributed tunneling steps. Experiments were conducted in two different regimes, both at constant negative gate voltage V g .…”

Reverse Intersystem Crossing of Single Deuterated Perylene Molecules in a Dibenzothiophene Matrix

“…Both the singlet and triplet of DBThio are higher in energy than the excited singlet state of perylene. The higher electronic energy levels of the host prevent intermolecular ISC, which is responsible for efficient quenching of single‐molecule fluorescence of perylene in anthracene [22] and of terrylene in anthracene [24] …”

“…So far, the 0–0 zero‐phonon line (ZPL) for the phosphorescence of perylene‐doped matrices has been detected solely for perylene in anthracene [22] and was determined to be around 12844±1 cm −1 , blue‐shifted by 472 cm −1 compared to the origin of phosphorescence found for a pure perylene crystal [23] . Unfortunately, fluorescence from single perylene molecules in anthracene could not be detected, probably because of intermolecular ISC [24] . For future studies on the phosphorescence of perylene in the dibenzothiophene matrix, we chose to study deuterated perylene in this work, instead of the commonly employed hydrogenated perylene.…”

Design and synthesis of aromatic molecules for probing electric fields at the nanoscale

“…In 2001, one of us has suggested using organic molecules as nanoprobes to measure charge distributions in organic semiconductors [4]. In follow-up experiments, we demonstrated the optical detection of trapped charges in organic crystals [5]. Other theoretical modelings have shown the possibility of detecting charge displacements of merely 10 pm by triangulation methods [6].…”