## 1 Introduction  
Among the Al\({}^{\Pi}\)-BVI semiconducting compounds [1; 2; 3], Cadmium Telluride (CdTe) is a P-type semiconductor with excellent physical and chemical properties [4], and is commonly used as photoabsorbing layer within optoelectronic devices such as infrared windows [5], electro-optic modulators [6], electroluminescent diodes [7], nuclear detectors [8], and solar cells [9]. For the latter category, the ideal band gap of CdTe (1.51 eV), as well as its outstanding stability against ionizing radiations (including cosmic rays), render it particularly interesting for both terrestrial and space-based solar photoconversion applications [10; 11]. In such scenarios, the photovoltaic element typically relies on a \"substrate\"-type configuration, in which the CdTe absorber is synthesized on top of a back-electrode typically made of a thin film of gold (Au), copper (Cu), or an AuCu combination [12; 13]. Consequently, a finite Schottky barrier inherently appears at the interface between the CdTe layer and the metallic film, potentially lowering the photogenerated charge carriers' collection and hence diminishing the power conversion efficiency (PCE) of these kind of thin film-based solar cells. Unfortunately, the properties of this interface are not simply affected by the metal work function and semiconductor band structure, and depend considerably on the initial surface morphology of the materials. For instance, the Schottky barrier height can be decreased by carefully optimizing the contact interface between the layers in order to enhance the performance of such solar cells [14]. Although these systems have been widely studied theoretically [14; 15], little has been reported regarding the experimental optimization of metal/CdTe heterojunctions for photovoltaic applications [16]. In this regard, by exploiting the advantages of up-to-date nanotechnologies it may be possible to obtain an improved interface by first creating a large array of vertically-aligned metallic nanowires (NWs) acting as a back-electrode, then fully embedding them within a consistent CdTe layer to ultimately secure a considerably enlarged electrically-active medium. Furthermore, the fabrication of \"brush\"-like electrodes is of particular interest for \"substrate\"-type photovoltaic structures based on semiconducting A\({}^{\text{II}}\)-BVI heterojunctions, as such perpendicular metallic NWs can be designed to approach the spatial charge region. Hence, they can be expected to play an important role in the charge collection mechanism, currently one of the limiting factors in achieving high efficiency from this type of solar cells [17]. However, the design of such well-controlled arrays of one-dimensional (1D) nanoarchitectures in a low-cost manner and with easily tunable geometrical features faces several limitations. Thus far, complex patterning methods such as electron-beam lithography, nanoimprinting, and nanosphere lithography have been employed to create vertically-aligned NWs with excellent spatial and geometric control; however, their fabrication involves high costs and time-consuming methods [18; 19; 20]. Alternatively, more cost-effective methods have been developed entailing an electrochemical synthesis approach within a suitable nanoporous template, such as track-etched polycarbonate (PC) or anodic aluminum oxide (AAO) membranes, where the resulting array of NWs represents an inverse replica of the initial nanoporous host [21; 22]. AAO is generally preferred thanks to its dense and highly-ordered hexagonally-packed nanopore arrangement, which favourably compares to the typical random distribution and low-density profile of the nanopores within a PC template. In addition, facile control of the nanopores' geometrical aspect by simple regulation of the anodization parameters, as well as the possibility of generating thin supported AAO nanoporous films which adhere well on various substrates, render this template-based technology suitable for cost-effective preparation of dense arrays of parallel vertically-standing NWs.