N-type, highly conductive CuO:In3+ films magnetron reactively sputtered at different reactive pressures

•N-type, highly conductive CuO:In3+ films are magnetron reactively sputtered.•Effect of reactive pressure is studied on the film's properties.•Roles In3+ plays in CuO:In3+ are proposed.•A conducting transition from n to p is observed at 1.8 Pa Preact.•Crystal lattice constants and lattice strains are calculated and analyzed. CuO is p-type conductive in nature because of its native point defects, and thus n-type, highly conductive CuO is difficult to obtain due to these native point defects. The introduction of trivalent metallic ions into CuO may deal with the problem. Thus in this work, non-stoichiometric n-type CuO:In3+ thin films are magnetron reactively sputtered at 25 °C (room temperature) and at different reactive pressures (Preact). Compared with CuO thin films, the CuO:In3+ thin films have considerably small electrical resistivity, thereby making CuO:In3+ film a potential candidate of light-absorbing materials in heterojunction solar cells. The high Preact helps improve the crystallization and mobility of the films by the weakened bombardment upon the film surface from the sputtered particles, and by the reduction of the free carrier concentration, respectively. The introduction of In3+ into CuO is more favorable to form n-type and high conduction by partial substitution of Cu by In3+. In addition, a conducting transition from n type to p type is observed at 1.8 Pa Preact. The 1.2 Pa Preact is more suitable for n-type CuO:In3+ for utilization in the photovoltaic application.