Effects of Temperature and Light Illumination on the Current–Voltage Characteristics of Molecular Self-Assembled Monolayer Junctions

Abstract

We systematically studied the charge transport properties of a series of self-assembled monolayer crossbar junctions with different alkanethiol and conjugated molecules, respectively. The junction was fabricated using a soft stamp-printing method. Current–voltage characteristics were measured at varied temperatures between 300 down to 90 K under different light illumination conditions. Strong temperature dependence and optoelectronic switching phenomena were observed in the as-fabricated junctions in both dark and light situations. To understand the charge transport mechanism, the Simmons and Fowler–Nordheim tunneling were used to analyze the experimental data. The distinctly different adsorbing nature of the top printed Au/molecule interface in the crossbar junctions is shown to play a dominant role in causing the asymmetric transport behavior. The charge injection barrier is strongly dependent on both the substrate temperature and the molecular length/conjugation structures. The barrier decreases with the increase of the substrate temperature and/or the molecular length, while a conjugated molecular structure can obviously enhance the junction charge transport. Our work may offer some useful information for developing molecular electronic devices.

Photoconductivity enhancement and charge transport properties in a conjugated polyelectrolyte/carbon nanotube hybrid studied by scanning probe microscopy

“…At negative bias, the changes in 4 0 are different at different wavelengths and the decrease in L is small. The observations at positive bias are consistent with the literature results, 65 suggesting a photoinduced electron transfer process from PTETDA to the MWCNT. 22,23 The photocurrent was mainly generated by the photogenerated charge carriers, reducing 4 0 .…”

“…The charge transport mechanisms in nanomaterials may be described by different models, which include Simmons tunneling, Fowler-Nordheim tunneling, hopping conduction, Poole-Frenkel emission and thermionic emission. 65 Different transport mechanisms have their unique I-V characteristics. The I-V data were t into different models to check the goodness of t and if the extracted physical quantities are meaningful.…”

“…Otherwise, the Simmons model should t to the I-V data at negative and positive biases separately. 65 G characterizes the symmetry of the charge transport. Under dark conditions, for pristine MWCNTs, G was calculated to be 2.6 AE 0.1 and for the PTETDA/MWCNT, it was 1.8 AE 0.1.…”

“…22,23 The photocurrent was mainly generated by the photogenerated charge carriers, reducing 4 0 . 65 Illumination may also increase the image force, thereby reducing both 4 0 and L by rounding off the corners of the effective tunneling barrier. 82 In contrast, at negative bias, the increase in 4 0 upon illumination is inconsistent with the literature result.…”

Enhanced performance through trap states passivation in quantum dot light emitting diode

“…Based on the correlation between current density and voltage and the dependence of current density on the temperature, we believe that the Poole-Frenkel emission is the charge transport mechanism in QLEDs, therefore trap states play an important role. [20,21] Poole-Frenkel effect describes the increase of the thermal emission rate of carriers in an external electric field due to the reduction of the barrier. Take the electron emission as an example, in the absence of an electric field, the minimum energy for an electron to escape from a trap state is qΦt, n (where q is the elementary charge).…”