The present invention describes a method of producing a photovoltaic solar cell with stoichiometric p-type copper indium gallium diselenide (CuInxGa1-xSe2) (abbreviated CIGS) as its absorber layer and II-IV semiconductor layers as the n-type layers with electrodeposition of all these layers. The method comprises a sequence of novel procedures and electrodeposition conditions with an ionic liquid approach to overcome the technical challenges in the field for low-cost and large-area production of CIGS solar cells with the following innovative advantages over the prior art: (a) low-cost and large-area electrodeposition of CIGS in one pot with no requirement of post-deposition thermal sintering or selenization; (b) low-cost and large-area electrodeposition of n-type II-VI semiconductors for the completion of the CIGS solar cell production; and (c) low-cost and large-area deposition of a buffer layer of CdS or other compounds with a simple chemical bath method.