关键词: CuGaSe$_{2}$ thin films, CuGa$_{3}$Se$_{5}$, Cu$_{2 - x}$Se

Abstract: Polycrystalline CuGaSe$_{2}$ thin films on Mo-coated soda-lime glass substrates have been synthesized by co-evaporation process from Cu, Ga and Se sources. Structural and electrical properties of the as-grown CuGaSe$_{2}$ films strongly depend on the film composition. Stoichiometric CuGaSe$_{2}$ is fabricated, as indicated by x-ray diffraction spectroscope (XRD) and x-ray fluorescence (XRF). A two-phase region is composed of CuGaSe$_{2}$ and Cu$_{2 - x}$Se phases for Cu-rich films, and CuGaSe$_{2}$ and CuGa$_{3}$Se$_{5}$ phases for Ga-rich films，respectively. Morphological properties are detected by scanning electron microscope (SEM) for various compositional films, the grain sizes of the CuGaSe$_{2 }$films decrease with the extent of deviation from stoichiometric composition. Raman spectroscopy of Cu-rich samples shows that there exist large Cu-Se particles on the film surface. The results from Hall effect measurements for typical samples indicate that CuGaSe$_{2}$ films are always of p-type semiconductor from Cu-rich to Ga-rich. Stoichiometric CuGaSe$_{2}$ films exhibit relatively large mobility than any other compositional films. Finally, polycrystalline CuGaSe$_{2}$ thin film solar cell with a best conversion efficiency of 6.02% has been achieved under the standard air mass (AM)1.5 spectrum for 100 mW/cm$^{2 }$ at room temperature (aperture area, 0.24 cm$^{2})$. The open circuit voltage of the CuGaSe$_{2}$ solar cells is close to770 mV.

Key words: CuGaSe$_{2}$ thin films, CuGa$_{3}$Se$_{5}$, Cu$_{2 - x}$Se