ZnO exhibits a remarkable potential application in organic solar cells as an electronic transfer layer.However,the large numbers of defects on nanomaterials surface will trap electron and then decrease the photocurrent of the device.In this research,we fabricated differe nt sizes of ZnO nanoparticles under different reaction temperatures.The impact of the particle size on the surface defects is further studied.The morphologies and optical properties are researche d by transmission electron microscopy (TEM),ultraviolet-visible absorption spectra and the fluore scence spectra.Analysis results showed the size and the specific surface area increase with the increase of reac tion temperature,while the defect density of ZnO nanoparticles is decreased.Finally,ZnO nanoparticle s with different reaction temperatures were incorporated in the organic photovoltaic devices as electron c onductive layer,and the optimized device (60℃) shows the highest power conversion efficiency of 3.05%. It is indicated that the grown particles result in the decrease of surface defects density,which is favo rable to the electron transfer and device performance improvement.