Towards a unified description of the charge transport mechanisms in conductive atomic force microscopy studies of semiconducting polymers

Abstract

In this work, conductive atomic force microscopy (C-AFM) is used to study the local electrical properties in thin films of self-organized fibrillate poly(3-hexylthiophene) (P3HT), as a reference polymer semiconductor. Depending on the geometrical confinement in the transport channel, the C-AFM current is shown to be governed either by the charge transport in the film or by the carrier injection at the tip-sample contact, leading to either bulk or local electrical characterization of the semiconducting polymer, respectively. Local I-V profiles allow discrimination of the different dominating electrical mechanisms, i.e., resistive in the transport regime and space charge limited current (SCLC) in the local regime. A modified Mott-Gurney law is analytically derived for the contact regime, taking into account the point-probe geometry of the contact and the radial injection of carriers. Within the SCLC regime, the probed depth is shown to remain below 12 nm with a lateral electrical resolution below 5 nm. This confirms that high resolution is reached in those C-AFM measurements, which therefore allows for the analysis of single organic semiconducting nanostructures. The carrier density and mobility in the volume probed under the tip under steady-state conditions are also determined in the SCLC regime.

Investigation of Electroactive and Antibacterial Properties of Polyethersulfone Membranes Blended With Copper Nanoparticles

“…However, it can be also seen that the 2% CuNPs blended membrane's surface has different pore shapes at different sizes. C‐AFM studies were used for the investigation of electrical conductance ability of copper blended membranes . C‐AFM images display surface conductivity of copper blended membranes.…”

Semiconducting Polymer Thin Films Used in Organic Solar Cells: A Scanning Tunneling Microscopy Study

“…pc‐AFM measurements provide insights of the OPVs nanoscale morphology and their local electrical properties simultaneously; further, from local current density ( J – V ) curves measurements the hole mobility through the film can be extracted, mobility value is an important parameter for charge transport because high values are desired in order to improve the OPV performance . These pc‐AFM determinations provide additional and complementary information to the STM analysis regarding nanoscale morphology and its correlation with the local PV performance . Device architecture was ITO/PEDOT:PSS (P VP AI 4083)/P3HT:[70]PCBM/PFN with a thickness of ≈40 nm for PEDOT:PSS, ≈100 nm for the active layer (area = 0.07 cm 2 ) and ≈5–10 nm for PFN (used as EEL) and, as top electrode, an AFM tip with gold conductive coating was used.…”

Exploring the Capabilities of Scanning Microwave Microscopy to Characterize Semiconducting Polymers

“…In this work, SMM is applied on poly(3-hexylthiophene-2,5-diy) (P3HT) [1]. P3HT remains a reference hole transporting a semiconducting polymer in OPV, as the combination of the relative stability, the nanostructural tunability [28] and the decreasing production costs of the material with the sufficient photovoltaic performances of the devices, make it a pertinent case-study for material validations later to be extended to more specific structures as foreseen in different industrial applications. As the sensitivity of SMM to the variations of electrical properties in P3HT is observed, the choice of experimental parameters and the mechanisms ruling the different S 11 signals recorded by the Keysight Power Network Analyzer (PNA) must be elucidated to reach meaningful properties of the materials under study.…”