Effect of the Cadmium Telluride Deposition Method on the Covering Degree of Electrodes Based on Copper Nanowire Arrays

Abstract

In this work, we report the preparation of nanostructured electrodes based on dense arrays of vertically-aligned copper (Cu) nanowires (NWs) to be subsequently covered by cadmium telluride (CdTe) thin films, with great potential to be used within “substrate”-type photovoltaic cells based on AII-BVI heterojunctions. In particular, the multi-step preparation protocol presented here involves an electrochemical synthesis procedure within a supported anodic aluminum oxide (AAO) nanoporous template for first generating a homogeneous array of vertically-aligned Cu NWs, which are then further embedded within a compact CdTe thin film. In a second stage, we tested three deposition methods (vacuum thermal evaporation, VTE; radio-frequency magnetron sputtering, RF-MS; and electrochemical deposition, ECD) for use in obtaining CdTe layers potentially able to consistently penetrate the previously prepared Cu NWs array. A comparative analysis was performed to critically evaluate the morphological, optical, and structural properties of the deposited CdTe films. The presented results demonstrate that under optimized processing conditions, the ECD approach could potentially allow the cost-effective fabrication of absorber layer/collecting electrode CdTe/Cu nanostructured interfaces that could improve charge collection mechanisms, which in turn could allow the fabrication of more efficient solar cells based on AII-BVI semiconducting compounds.

Effect of the back contact electrode on the performances of the ultra-thin photovoltaic cells based on the CdS/CdTe heterojunction

“…The large values of both CdS and CdTe's absorption coefficients [6] together with their direct energy bands alignment; i.e. [7] and 1.43 − 1.45 eV for CdTe [8], for bulk materials and with small variations for confined structures, increased and varied the assigned applications. Versatility in terms of easy building architectures is another attribute of CdS and CdTe materials, so the optimization of CdS/CdTe device performances may be performed by different approaches; i.e.…”

“…E. Artegiani et al analysed the influence of the transparent electrode on the photo-electrical response and time stability for a superstrate structure by testing an indium tin oxide/zinc oxide (ITO/ZnO) configuration compared to individual ITO and/or fluorine tin oxide (FTO) [9], while X. Mathew et al took a step forward and fabricated CdS/CdTe devices onto flexible substrates [10]. The use of different substrates was possible because both CdS and CdTe thin films can grow by assorted methods, including thermal evaporation [8,[11][12][13], radio-frequency (RF) magnetron sputtering [8,[14][15][16], close-space sublimation [17,18], electrodeposition [8,19,20], and molecular beam epitaxy [21,22]. Despite so many obtaining alternatives, the literature reports indicate thermal evaporation as the main approach and due to this, the thickness of samples is usually about 2 − 3 μm.…”