TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Process: Alternatively, removing non-bonding compounds from respective absorber layers of each of absorber substrates during a cleaning process, involves setting conditions of a solution in a solvent tank used to clean the non-bonding compounds from the absorber layers of the absorber substrates; calculating a thickness of boundary layers formed on the absorber layers in the solvent tank during the cleaning process; setting of spacing between the absorber substrates and circulation speed of the solution in the solvent tank during the cleaning process; and immersing and cleaning the absorber substrates in the solvent tank under of the set conditions, spacing and circulation speed of the solution. The non-bonding compounds are formed at grain boundaries of polycrystalline material of the absorber layer of the absorber substrate during fabrication of the absorber substrate. The method further involves setting pH value of the solution at 4-12; setting temperature of the solution at 25-85 degrees C; adding solvent into the solution so as to reduce viscosity of the solution; and increasing the circulation speed of the solution to reduce the thickness of boundary layer thickness and increase flow speed of the solution. The method also involves: (a) arranging the absorber substrates in pairs, where the absorber substrates in each pair are immersed in the solution with their respective absorber layers facing each other; (b) setting the spacing between the pair of absorber substrates based on the thickness of the boundary layers formed on the absorber substrates to speed up the cleaning process; (c) setting the spacing between the pair of absorber substrates to be greater than twice the thickness of the boundary layers on the absorber substrates; and (d) setting the spacing between the pair of absorber substrates based on length of the absorber substrates. Preferred Components: The absorber layer comprises one of copper indium gallium selenide (CIGS) cadmium telluride (CdTe), copper indium diselenide (CulnSe2) (CIS), copper gallium diselenide (CuGaSe2)(CGS), Cu(In,Ga)(Se,S)2 (CIGSS), and amorphous silicon. The absorber substrate is an unfinished solar cell with the absorber layer uncovered and exposed for cleaning. The absorber substrates are arranged in pairs with the absorber substrates in each pair are immersed in the solution with their respective absorber layers facing each other. The spacing between the pair of absorber substrates is set based on the thickness of the boundary layers formed on the absorber substrates to speed up the cleaning process. The spacing between the pair of absorber substrates is set based on length of the absorber substrates for fast cleaning of non-bonding compounds on the absorber layers. Preferred Conditions: The conditions of the solution include content, pH value, and temperature of the solution. Preferred Parameter: The thickness of the boundary layers formed on the absorber layers is calculated based on hydrodynamics of the solution in the tank during the clean process.