Preparation And Study Of Copper Oxide And Indium-doped Copper Oxide Thin Films Via Direct-current Magnetron Sputtering

Copper oxide（CuO）is an environmentally friendly,non-toxic,inexpensive direct-band-gap semiconductor that has a promising application potential in many fields,especially in solar cells field.Hence in this study,intrinsic CuO and indium-doped CuO（CuO:In）films were prepared via direct-current magnetron sputtering,and the impacts of the experimental parameters,including oxygen-to-argon ratio,substrate temperature,sputtering power and reactive pressure were intensively studied on the microsture,the optical and electrical properties of the films.In addition,a perovskite solar cell structured with Ag/PCBM/perovskite/CuO/FTO was fabricated and tested in J-V characteristics.The main experimental results are listed as follows:（1）Single-phased CuO films with<-111>preferred orientation were prepared at a substrate temperature of 170°C.The compressive stress exist along the crystal axes a and b,whereas a stress transition in the films from compressive to tensile occurs along the axis c with increase of substrate temperature.The optical absorption edge value of the films varies in the range between 1.85 eV and 1.94 eV,and the slight blue shift of the optical absorption edge is attributed to the quantum size effect of the grains.（2）The CuO film,prepared at oxygen-to-argon ratio of 1:2 and substrate temperature≥300°C,has a single-phase structure,whereas the film has a strongest<111>preferred orientation at substrate temperature of 600°C.A conducting transition from p to n occurs at substrate temperature of 500°C,and the microstress of the films along the crystal axes a,b and c exhibit the tensile stress.The optical absorption edge of the films first slightly blueshifts,and then redshifts with increase of substrate temperature.The free carrier concentration of the films reaches the maximum value of 3.406×10¹⁹ cm^-3 at substrate temperature of 400°C.（3）The preferred<-111>-oriented CuO:In films were room-temperature prepared by changing the sputtering power.The CuO:In is still a direct-band-gap semiconductor.With increase of sputtering power,the preferred<-111>orientation of the films is enhanced to the maxima at sputtering power of 140 W.The microstress of films along the axes a,b and c is tensile stress,and the optical absorption edge is slightly redshifted with increase of sputtering power.A conducting transition from p to n occurs at sputtering power of 100 W.The maximum free carrier concentration maximum and mobility of the films are 9.333×10¹⁸ cm^-3 and 23.38 cm²s^-1V^-1,respectively.（4）The single-phased CuO:In films were room-temperature prepared at different reactive pressures.CuO:In is still a direct-band-gap semiconductor.The Increase of reactive pressure improves the crystallization and enhances the preferred<-111>orientation of the films under high sputtering power condition.The growth of the crystallites of the films show clear anisotropy along the crystal axis a,b and c.The free carrier concentration values of the films are all greater than 10¹⁸ cm^-3,and the conducting type transitions with reactive pressure.（5）CuO can be hole transportion layer for perovskite solar cells.A solar cell inversely structured with Ag/PCBM/perovskite/CuO/FTO has a power conversion efficiency of 1.3%,a short-circuit current of 3.26E-4 A and a fill factor of 40.1%.