Study of physical properties of copper oxide thin films prepared by spin coating for hole transport applications in perovskite solar cells

Annealing was employed at temperatures between 200 and 400 °C to tune the physical properties of copper oxide (CuO) thin films synthesized via the spin coating deposition technique. Different thin film characterization techniques, including XRD, Raman spectroscopy, SEM, ultraviolet (UV)–Vis spectroscopy, FTIR, hot probe conductivity, and IV measurements, were employed to study physical properties. XRD showed the polycrystalline structure of these thin films. In the analysis of UV–Vis spectra, a decrease in bandgap energy was observed, with values falling from 1.93 to 1.81 eV for CuO and from 2.76 to 2.66 eV for Cu2O, respectively. The Ag phonon modes at 299.22 and 304 cm−1 observed in the Raman shift confirm the formation of a pure CuO phase. FTIR spectra revealed the Cu–O stretching band at 759, 764, and 446 cm−1. SEM revealed the agglomeration of nanocrystallites along with the presence of large grains on the surface of thin films. The two-point hot probe technique showed that the conductivity of CuO thin films is p-type. Low resistivity values ranging from 0.1554 to 0.1028 Ω-cm were recorded. These findings suggest that CuO thin films can be effectively utilized as a hole transport layer in perovskite solar cells.