Metallic electrodes, as well as transparent electrodes, are responsible for the current flow from the photovoltaic cell into the circuit and therefore have a significant influence on its electrical parameters. Depending on geometry and architecture, we distinguish between electrodes in the form of thin horizontal tracks (busbar¹), as thin conductive wires (smart wire²) and the electrodes on the back of the cell (HIT³).
To ensure that the charge generated by the cell is transferred to the external circuit, it is important to have the lowest possible resistance between the semiconductor material that makes up the active layer of the cell and the metallic electrode. This resistance between the semiconductor and the metal can be linear or non-linear. The occurrence of linear (ohmic) or non-linear (Schottky) conductivity is determined by the parameters of the materials used. The contact should not influence the current-voltage characteristics of the cell [1]. In practice, the resistance of a cell is influenced by the length of distance an electrical charge has to travel in a plate, an important parameter of electrode materials is the work function of an electron from a metal ( Fig. 1 based on [2]). The second parameter affecting the type of conductivity is the Fermi level of the semiconductor.

The most commonly used electrode material is silver, but other materials such as aluminium and copper are also being implemented. In CIGS cells, molybdenum and aluminium are used [3], [4].

The method most commonly used to apply contacts is screen printing. In order to maintain a large open area of the screen and to produce precise patterns, meshes with increasingly thin stainless-steel wires are used. The advantages of screen printing are the high throughput of the process and the wide availability of materials. Thin film technologies are also being developed (e.g., aerosol jetting).