Cuprous oxide (Cu2O) has many advantages. These advantages include a direct band gap (the forbidden band gap is 2.1 eV), Earth-abundance, no toxicity, low cost and high absorption coefficients, etc. Because of these advantages, cuprous oxide has the potential to be used in solar cells. Theoretical work predicts that the maximum efficiency of Cu2O pn homojunction solar cells can reach 20%. However, experimental work demonstrates that the maximum is less than 2%. The reason lies in the n-type layer in these homojunctions. The n-type layers in the homojunctions in the literature were all fabricated with electrodeposition. Electrodeposition can result in the surface accumulation of Cu 2+ ions. The Cu2+ ions make the layers to behave like n-type conduction, though the layers were actually of p-type. To realize the n-type conduction, we tried doping Cu2O with indium or zinc. The indium-doped Cu2O thin films were fabricated with reactive direct current magnetron sputtering. The two targets were circular copper and indium disks. The substrates were K9 glass and the gases were Ar and O2. By properly selecting the sputtering powering and gas flow rates, etc., pure-phase Cu2O doped with indium can be fabricated. The samples were characterized with various methods such as X-ray diffraction (XRD), etc. and the results were analyzed and discussed. The results show that the indium-doped Cu2O thin films are of n-type conduction below 400K and indium atoms are possible donors in Cu2O. Zinc-doped Cu2O thin films were also fabricated with reactive direct current magnetron sputtering and characterized with XRD, etc. Pure-phase Cu2O doped with zinc can also be fabricated. The results show that all zinc-doped samples are still of p-type conduction.