Transmission-based charge modulation microscopy on conjugated polymer blend field-effect transistors

Abstract

Charge modulation microscopy (CMM) is an electro-optical method that is capable of mapping the spatial distribution of induced charges in an organic field-effect transistor (OFET). Here, we report a new (and simple) implementation of CMM in transmission geometry with camera-based imaging. A significant improvement in data acquisition speed (by at least an order of magnitude) has been achieved while preserving the spatial and spectral resolution. To demonstrate the capability of the system, we measured the spatial distribution of the induced charges in an OFET with a polymer blend of indacenodithiophene-co-benzothiadiazole (IDTBT) and polyvinylcarbazole (PVK) that shows micrometer-scale phase separation. We were able to resolve spatial variations in the accumulated charge density on a length scale of 500 nm. We demonstrate through a careful spectral analysis that the measured signal is a genuine charge accumulation signal that is not dominated by optical artefacts.

The relationship between ionic-electronic coupling and transport in organic mixed conductors

“…The relative transmission intensity through PEDOT:PSS in the visible range (1.6 to 2.5 eV) is expected to be related to the concentration of absorbing neutral PEDOT chains (28,33). Thus, ∆T/T 0 images should provide quantitative information about the local change in hole concentration, p. To quantify the relationship between ∆T/T 0 and p, we measured the voltage-dependent transmission spectra (Fig.…”