Cyclic voltammetry and chronoamperometry were used to study the deposition process at the initial stage of Cu2O electrodeposition on indium tin oxide-coated glass. The current transient data and predicted values were analyzed by the instantaneous and progressive nucleation models under different electrolyte concentrations. The effects of the Cu2O nucleation mechanism on microstructure and photoelectric properties of Cu2O were investigated by X-ray photoelectron spectroscopy, X-ray diffractometry, scanning electron microscopy, ultraviolet visible spectrophotometry and fluorescence spectrophotometry. The results show that the electrochemical deposition process of Cu2O is irreversible and controlled by diffusion, and the diffusion coefficient was calculated to be 2.2 x 10(-6) cm(2).s(-1). The nucleation mechanism of Cu2O is related to the electrolyte concentration. When the concentrations of Cu(AC)(2) were 5 mM and 15 mM, the nucleation processes of Cu2O were consistent with the progressive nucleation and instantaneous nucleation models, respectively. Under the instantaneous nucleation mechanism, the prepared Cu2O displayed a uniform structure, composed of sword-shaped dendritic crystal. Compared to the progressive nucleation, the purity of the Cu2O was higher, the bandgap narrower (2.006 eV), and the photoluminescence intensity higher. The Cu2O had a high carrier density (4.9 x 10(22) cm(-3)) and a low charge transfer resistance (127.27 K Omega.cm(2)). It exhibits superior photoelectric performance. (c) The Author(s) 2017. Published by ECS. All rights reserved.