NOVELTY - Solution-based deposition process for depositing an absorber layer on a substrate involves contacting hydrazine and a source of copper (Cu), indium (In), gallium (Ga), selenium (Se), and optionally sulfur (S); coating the solution on substrate to produce a coated substrate; and heating the coated substrate to produce absorber layer; where absorber layer comprises a doped or undoped composition of Cu, In, Ga, Se.    USE - For depositing an absorber layer (claimed) useful in production of photovoltaic device e.g. solar cell.    ADVANTAGE - In the solution-based approaches, high vacuum conditions are not required, thus reducing fabrication costs and renders the fabrication of large area devices much more convenient. The deposition process is less energy intensive, can be prepared at room temperature and can be simply solution-processed e.g. spin coated, ink-jet printed, doctor bladed, stamped, dip coated onto the substrate. Materials utilization efficiency is generally much higher for present method, such that materials costs and processing wastes are kept as small as possible. The present solution-based approach has higher production throughput and is compatible with roll-to-roll and large area processing. The present solution-based technique does not involve oxygen or oxides, and does not require anneal in a chalcogen-containing atmosphere. The present method is faster, cleaner and simpler than electrochemical approaches. The present solution-based technique enables facile incorporation of dopants such as Al, Sb, Na, or Te, either in uniform or in a graded manner as desired. The method is simple to implement and, permits one to tailor the chemical composition of the absorber layer by simply changing the ratio of elements in the solution or dissolving other elements, such as, Ga, Na, and Sb, into the deposition solution. Such incorporation facilitates grain growth and optimization of the absorber layer and can improve the electrical characteristics of the device. The precursor and solution of the method employ only the metal chalcogenide, chalcogen and hydrazine (or a hydrazine-like compound), thus eliminates many sources for potential film impurities, including carbon, oxygen, and halides. The method is very simple and potentially very low cost, as no vacuum-based treatments or depositions are required. There is also no need to carefully prepare nanoparticles prior to the fabrication. The optimized photovoltaic devices according to the present method are lower cost and are expected to operate with better electrical characteristics than analogous devices in which the absorber layer is deposited using other solution-based approaches.    DETAILED DESCRIPTION - Solution-based deposition process for depositing an absorber layer on a substrate involves contacting hydrazine and a source of Cu, In, Ga, Se; coating the solution on substrate to produce a coated substrate; and heating the coated substrate to produce absorber layer; where absorber layer comprises a doped or undoped composition of formula Cu1-yIn1-xGaxSe2-zSz.    x=0-1;    y=0-0.15;    z=0-2.