Method of making optoelectric devices

A method of preparing an optoelectric device, comprising: (a) providing a substrate on which is formed a first electrode layer; (b) forming an electron transport layer according to the following method: i) forming a film of a coating ink comprising zinc acetate in aqueous solution; ii) drying the film; iii) heating the dry film such that the zinc acetate is substantially converted to ZnO; (c) forming an active layer according to either of the following methods: i) applying a coating ink comprising a light-harvesting polymer and a fullerene to the electron transport layer and drying the coating ink layer; or (ii) 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 according to the following method: i) coating the active layer with a solution comprising a hole transporting compound, water and an alcohol to form a film; ii) drying the film to form a hole transport layer; (e) forming a second electrode layer on the hole transport layer.