Chlorine-doped n-type cuprous oxide films fabricated by chemical bath deposition

The development of n-type Cu₂O has become essential for realizing high-efficiency PV devices based on Cu₂O homojunctions, thereby avoiding the numerous efficiency-reducing defects common in heterojunctions. To the best of our knowledge, we are the first to fabricate chlorine (Cl)-doped cuprous oxide (Cu₂O:Cl) thin films on a copper (Cu) substrate by using the chemical bath deposition (CBD) method. The Cu ₂O:Cl films were prepared using copper sulfate (CuSo₄) solution with the addition of copper chloride (CuCl₂) as a Cl- source. After the molar ratio of CuCl₂ to CuSo₄ ([CuCl₂]/[CuSo₄]) was varied from 0 to 2.01, hot-point probe measurements showed n-type conductivity for all the Cu₂O films produced by CBD. X-ray diffraction patterns indicate that the as-grown Cu ₂O:Cl films have a sphalerite structure with a dominant plane orientation of Cu₂O(111) parallel to the substrate surface for [CuCl₂]/[CuSo₄] of less than 1.19, while the CuCl(111) phase became dominant when [CuCl₂]/[CuSo₄] was greater than 1.19. Moreover, low-temperature photoluminescence (PL) measurements conducted at 5 K demonstrated an emission band at 1.902 eV, related to Cl doping, in addition to the emission band at 1.715 eV, attributed to doubly ionized oxygen vacancies. We found that the Cl-related PL emission was intensified with increasing amounts of Cl involved. The incorporation of Cl into the lattice of Cu₂Owas also confirmed by X-ray photoelectron spectroscopy. Our findings indicate that n-type Cu₂O:Cl films with a resistivity ranging from 40-50 ω. cm can be produced on Cu substrate by the CBD method.