The effect of composition on structural and electronic properties in polycrystalline CuGaSe2 thin film

• 来源期刊: 中国物理B(英文版)
• 关键词: CuGaSe2 thin films CuGa3Ses Cu2-xSe
• 年，卷（期）: 2008,（8）
• 页码范围: 3138-3142
• 页数: 5页
• 语种: 英文

摘要

Polycrystalline CuGaSe2 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 CuGaSe2 films strongly depend on the film composition. Stoichiometric CuGaSe2 is fabricated, as indicated by x-ray diffraction spec-troscope (XRD) and x-ray fluorescence (XRF). A two-phase region is composed of CuGaSe2 and Cu2-xSe phases for Cu-rich films, and CuGaSe2 and CuGa3Se5 phases for Ga-rich films, respectively. Morphological properties are de-tected by scanning electron microscope (SEM) for various compositional films, the grain sizes of the CuGaSe2films 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 CuGaSe2 films are always of p-type semiconductor from Cu-rich to Ga-rich. Stoichiometric CuGaSe2 films exhibit relatively large mobility than any other compositional films. Finally, polycrystalline CuGaSe2 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/cm2 at room temperature (aperture area, 0.24cm2). The open circuit voltage of the CuGaSe2 solar cells is close to770 mV.