## 1 Introduction  
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. Today, the most promising ones are standing on the brink of industrial development. Additionally, despite pending issues such as durability, photovoltaic technologies exhibiting specification such as low fabrication cost, lightweight, mechanical flexibility, low environmental impact and short energy payback time can now be foreseen in a near future with specific cases of use. These technologies are very diverse and based on many different types of materials and combinations with continuous development towards higher performing devices. Among them, 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 therefore 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]. As these techniques are sensitive to the loss of reflected transmitted microwaves in a (semi-)conducting medium and can be carried out without mechanical contacts, remote measurements can be considered on structures capped with encapsulating layers, as required in these devices to ensure sufficient stability.  
This also makes them suitable techniques for future implementation in industrial environments as in-line feedback tools in process evaluation. Scanning microwave microscopy (SMM) consists of a microwave-based probing method integrated in a scanning probe microscope [14; 15; 16; 17; 18; 19; 20], thus allowing for two-dimensional mapping of electronic properties at the nanoscale. It can be used to investigate dielectric [21; 22; 23] and conductivity [24; 25; 26] properties. On organic-inorganic trihalides perovskites, Kelvin Force Microscopy (KFM) was also proposed to correlate the material's (photo)conductivity with its structural and morphological properties as they are well known to strongly affect the performances of the corresponding photovoltaic devices [27]. Meanwhile, the ability of dielectric resonators to electrically characterize organic conductors was demonstrated to operate at 9 GHz on a benzothiophene derivative [13]. Similar quantitative studies at the nanoscale are, however, lacking. In this work, SMM is applied on poly(3-hexylthiophene-2,5-diy) (P3 HT) [1]. P3 HT 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 P3 HT 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. Different key parameters including the microwave frequency and the operating setpoint compared to the adjacent frequency are explored. SMM capability to probe simultaneously and independently GHz dielectric properties, i.e., microwave conductive and capacitive mechanisms is evidenced. These mechanisms include depth probing, mesoscopic transport and trapping mechanisms, thus demonstrating versatile capability for the study of OPV thin films both in scientific and industrial operating environment.