Abstract
Standing at the meeting between solid state physics and optical spectroscopy, microwave characterization methods are efficient methods to probe electronic mechanisms and mesoscopic transport in semiconducting polymers. Scanning microwave microscopy, augmented with a Mach-Zehnder interferometer detection unit to allow for the probing of high impedance structures was applied on poly(3-hexylthiophene-2,5-diy) and exhibited high sensitivity while operating at the nanoscale. Provided a well-defined experiment protocol, S11 phase and amplitude signals are shown to lead simultaneously yet independently to probing the variations of the dielectric properties in the materials, i.e., conductive and capacitive properties, respectively, upon applied DC gate bias. Adjusting the operating microwave frequency can also serve to probe carrier trapping mechanisms.
Highlights
The increasing demand for sustainable and renewable energy to cope with incoming crucial environmental challenges has been promoting alternative photovoltaic technologies since the turn of the century
Scanning microwave microscopy (SMM) equipped with a Mach-Zehnder interferometer to allow for 50 Ω free detection system and probing high impedance semiconducting materials was applied to electrically characterize P3HT as a reference semiconducting polymer in a Metal-Insulator-Semiconductor structure
Provided the operating setpoint is appropriately adjusted in the vicinity of a chosen interferometric fringe to ensure enough sensitivity (|fOP − f0 | < 100 kHz) and avoid cross-talking artifacts (|fOP − f0 | > 10 kHz), performance network analyzer (PNA) phase and amplitude signal variations could be simultaneously and independently correlated to the conductive and capacitive mechanisms modifying the properties of P3HT upon bias
Summary
The increasing demand for sustainable and renewable energy to cope with incoming crucial environmental challenges has been promoting alternative photovoltaic technologies since the turn of the century. Hybrid perovskite and bulk heterojunction organic photovoltaic (OPV) technologies count among the most promising, considering the achieved performances and the huge scientific forces at work to conceive materials and unravel their complex properties [1,2,3,4] This requires high-resolution characterization techniques among which microwave-based methods were recently proven efficient for probing conductive properties of semiconducting materials [5,6,7,8,9] in addition the initial craze involving macroscale techniques since the beginning of the century [10,11,12,13]. These mechanisms include depth probing, mesoscopic transport and trapping mechanisms, demonstrating versatile capability for the study of OPV thin films both in scientific and industrial operating environment
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