Characterization of the TCO Layer on a Glass Surface for PV IInd and IIIrd Generation Applications

Abstract

In the dynamic field of photovoltaic technology, the pursuit of efficiency and sustainability has led to continuous novelty, shaping the landscape of solar energy solutions. One of the key elements affecting the efficiency of photovoltaic cells of IInd and IIIrd generation is the presence of transparent conductive oxide (TCO) layers, which are key elements impacting the efficiency and durability of solar panels, especially for DSSC, CdTe, CIGS (copper indium gallium diselenide) or organic, perovskite and quantum dots. TCO with low electrical resistance, high mobility, and high transmittance in the VIS–NIR region is particularly important in DSSC, CIGS, and CdTe solar cells, working as a window and electron transporting layer. This layer must form an ohmic contact with the adjacent layers, typically the buffer layer (such as CdS or ZnS), to ensure efficient charge collection Furthermore it ensures protection against oxidation and moisture, which is especially important when transporting the active cell structure to further process steps such as lamination, which ensures the final seal. Transparent conductive oxide layers, which typically consist of materials such as indium tin oxide (ITO) or alternatives such as fluorine-doped tin oxide (FTO), serve dual purposes in photovoltaic applications. Primarily located as the topmost layer of solar cells, TCOs play a key role in transmitting sunlight while facilitating the efficient collection and transport of generated electrical charges. This complex balance between transparency and conductivity highlights the strategic importance of TCO layers in maximizing the performance and durability of photovoltaic systems. As the global demand for clean energy increases and the photovoltaic industry rapidly develops, understanding the differential contribution of TCO layers becomes particularly important in the context of using PV modules as building-integrated elements (BIPV). The use of transparent or semi-transparent modules allows the use of building glazing, including windows and skylights. In addition, considering the dominant position of the Asian market in the production of cells and modules based on silicon, the European market is intensifying work aimed at finding a competitive PV technology. In this context, thin-film, organic modules may prove competitive. For this purpose, in this work, we focused on the electrical parameters of two different thicknesses of a transparent FTO layer. First, the influence of the FTO layer thickness on the transmittance over a wide range was verified. Next, the chemical composition was determined, and key electrical parameters, including carrier mobility, resistivity, and the Hall coefficient, were determined.