Photovoltaic cells and panels are multilayer structures ( Fig. 1, Fig. 2 ).

Some cell components come in a few generations. In addition to the conceptually different active layers in which the photovoltaic phenomenon occurs, each cell includes contact electrodes. The cell electrode located on the side of the Sun may have the form of a thin-film transparent electrode, strips of silver and aluminum paste (busbar electrode), or thin conductive wires (smart wire). The counter-electrode is usually shaped like a metallic aluminium layer. There are also constructions in which both electrodes are placed at the back (so-called HIT, Heterojunction with Intrinsic Thin Layer). By the top electrode we still mean the layer on the Sun side (on which the Sun's radiation falls), while by the bottom electrode we mean the electrode not directly illuminated by the Sun. An encapsulant is used to provide insulation, encapsulation and protection against mechanical and chemical damage to the cell. Polymer films are used for this purpose. The most common material is EVA (ethylene vinyl acetate). The top surfaces in cells are covered with anti-reflective layers [1].
The functions of these layers are detailed in the sections: 4.4 Antireflective layers, 4.5 Passivation layers.