关键词: CdxTe薄膜, 双源共蒸发, CdTe太阳电池

Abstract:

Cd_xTe thin films with different x values were deposited for the first time through controlling evaporation rates of CdTe and Te powder by vacuum co-evaporation. Then the films were annealed in N₂ atmosphere at 185℃. The morphological, structural, optical, and electrical properties of the Cd_xTe films were investigated by X ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible absorption spectrum and temperature dependence of the dark conductivity. UV-visible absorption spectrum demonstrates that energy band gaps (E_g) of different Cd_xTe films change from 0.99 eV to 1.46 eV. The absorption edges of different Cd_xTe films move towards longer wavelength and their transmittances reduce dramatically as the x value decreases from 0.8 to 0.2. XRD shows that as-deposited Cd_xTe thin films are amorphous when value of x is less than 0.6. Otherwise, Cd_xTe thin films are crystalline whose CdTe phase with preferential in (111) direction while value of x is approaching 1. The result indicates that annealing treatment is helpful for the films shifting from amorphous to polycrystalline. All the films exhibit p-type conductivity and the conductivity increases firstly as temperature rises. But it becomes abnormal while the temperature reaches a certain point. Data from this research suggest that Cd_xTe thin films can potentially be used for CdTe thin film solar cells to improve the long wavelength response.

Key words: CdxTe thin films, co-evaporation, CdTe solar cells