Effect of Cu doping on the properties of ZnTe:Cu thin films and CdS/CdTe/ZnTe solar cells
- Department of Physics, Colorado School of Mines, Golden, Colorado 80401 (United States)
The effects of Cu doping concentration and post-deposition annealing treatment on the properties of ZnTe thin films were investigated in an effort to decrease the Cu doping concentration and improve the long-term stability of CdS/CdTe/ZnTe solar cells. The structural, compositional, and electrical properties were studied systematically using x-ray diffraction (XRD), electron microprobe, Hall effect and conductivity measurements. XRD measurements indicated that the crystalline phase of as-deposited and low-temperature annealed ZnTe films is dependent on Cu doping concentration. Low-Cu-doped films exhibited zincblende phase, whereas high-Cu-doped films showed wurtzite phase. After annealing at high temperature ({ge}350{degree}C), all films exhibited zincblende structure. Electron probe microanalysis revealed a deficiency of cations in low-Cu-doped films and an excess of cations in high-Cu-doped films. Hall effect measurements revealed a dependence of hole mobility on Cu doping concentration with the highest mobility (20cm{sup 2}/V{center_dot}s) obtained at a low Cu concentration. Carrier concentrations higher than mid-10{sup 16}cm{sup {minus}3} were obtained at a Cu concentration of 2 at. {percent} and relatively low annealing temperatures. Studies of the activation energy of dark conductivity suggested that intrinsic defects (e.g., Zn vacancies) are the dominant acceptors for Cu concentrations lower than 4.5 at. {percent}. Finally, ZnTe films with Cu concentrations as low as 1 at. {percent} were used successfully as a back contact layer in CdTe based solar cells. Fill factors over 0.70 were obtained using ZnTe films of low Cu concentrations. {copyright} {ital 1997 American Institute of Physics.}
- OSTI ID:
- 552864
- Report Number(s):
- CONF-961178--
- Journal Information:
- AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 394; ISSN 0094-243X; ISSN APCPCS
- Country of Publication:
- United States
- Language:
- English
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