NOVELTY - Preparing an optoelectric device, comprises: providing a substrate on which is formed a first electrode layer; forming an electron transport layer by forming a film of a coating ink, drying the film, and heating the dry film; forming an active layer by e.g. applying a coating ink; forming a hole transport layer on the active layer by coating the active layer with a solution comprising a hole transporting compound, water and an alcohol to form a film, and drying the film to form a hole transport layer; and forming a second electrode layer on the hole transport layer.    USE - The method is useful for preparing an optoelectric device, preferably a solar cell (all claimed).    ADVANTAGE - The method is cost effective, and produces the solar cell with excellent stability and environmentally friendly manner.    DETAILED DESCRIPTION - Preparing an optoelectric device, comprises: (a) providing a substrate on which is formed a first electrode layer; (b) forming an electron transport layer by (bi) forming a film of a coating ink comprising zinc acetate in aqueous solution, (bii) drying the film, and (biii) heating the dry film such that the zinc acetate is substantially converted to zinc oxide; (c) forming an active layer by either (ci) applying a coating ink comprising a light-harvesting polymer and a fullerene to the electron transport layer and drying the coating ink layer, or (cii) applying a coating ink comprising a soluble precursor of a light harvesting polymer, a fullerene and a solvent to the electron transport layer, drying the coating ink layer and treating the dried coating ink layer to convert the soluble precursor of a light-harvesting polymer into a light harvesting polymer that is substantially insoluble in the solvent comprised in the coating ink; (d) forming a hole transport layer on the active layer by (di) coating the active layer with a solution comprising a hole transporting compound, water and an alcohol to form a film, and (dii) drying the film to form a hole transport layer; and (e) forming a second electrode layer on the hole transport layer.