We report on the performance enhancement of n-type organic field-effect transistors (OFETs) through the use of gold source and drain electrodes that are both modified with rubidium carbonate (Rb2CO3) reducing the electron injection barrier. Devices are fabricated using n-channel N, N′-ditridecyl-3,4,9,10-perylenetetracarboxylicdiimide (PTCDI-C13) and a polymeric gate dielectric with various thicknesses of Rb2CO3, and the dependence of device's electrical performance on Rb2CO3 thickness is investigated. The device with 10 Å Rb2CO3 exhibits the best performance, and its mobility is five times higher than that of the device without Rb2CO3. UV–visible, x-ray and ultraviolet photoemission spectroscopy are used to investigate the interface between Rb2CO3 and PTCDI-C13, and we find that charge transfer from Rb2CO3 to PTCDI-C13 occurs, resulting in the reduction of the electron charge injection barrier from the gold electrode. The charge injection mechanism and OFET performance enhancement with Rb2CO3 are discussed in detail.