Monodisperse Cu and Cu2O nanoparticles (NPs) are synthesized using tetradecyl-phosphonic acid as a capping agent. Dispersing the NPs in chloroform and hexane at room temperature results in the formation of hollow Cu2O NPs and Cu@Cu2O core/shell NPs, respectively. The monodisperse Cu2O NPs are used to fabricate hybrid solar cells with efficiency of 0.14% under AM 1.5 and 1 Sun illumination.