Chemical treatment of crystalline silicon solar cells as a main stage of PV modules recycling

In recent years, photovoltaic systems have gained worldwide recognition and popularity as a environmentally friendly way of solving energetic problems. However, a problem of utilizing worn out photovoltaic systems, amount of which will rapidly increase in the future, is yet to be solved. Establishing a technology of recycling and reusing obsolete photovoltaic panels is a necessity. Photovoltaic modules of crystalline silicon solar cells are made of the following elements, in order of increasing mass: glass, aluminum frame, EVA copolymer transparent hermetizing layer, photovoltaic cells, installation box, Tedlar protective foil and assembly bolts. From an economic point of view, taking into account the price and supply level, pure silicon, which can be recycled from PV cells, is the most valuable building material used. A way of utilizing obsolete and out-of-use photovoltaic silicon cells has been presented. Because of a high quality requirement for silicon obtained, chemical processing is the most important stage of recycling process. Conditions for chemical treatment need to be precisely adjusted in order to achieve the required purity level of recycled silicon. For crystalline silicon based PV systems, a series of etching processes has been performed on, in order: electric connectors, ARC and n-p junction layer. The compositions of etching solutions were individually adjusted for different silicon cell types. Efforts were taken to formulate a universal etching solution composition, yet the results showed that a solution modification is required for different types of PV cells.