Title page for etd-0805116-140206


[Back to Results | New Search]

URN etd-0805116-140206
Author Li-Kuan Liu
Author's Email Address No Public.
Statistics This thesis had been viewed 5342 times. Download 1 times.
Department Materials and Optoelectronic Science
Year 2015
Semester 2
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title Preparation of CuInSe2 epitaxial films for ultrathin Si solar cell
Date of Defense 2016-07-29
Page Count 67
Keyword
  • p-CuGaSe2/n-Si/n-CuInSe2
  • PC1D simulation
  • extrinsic doping of Zn
  • ultra-thin Si wafers
  • n-Si/p-Si/p-CIS
  • Abstract As the Si wafer tends to decrease in thickness for current developments of crystalline Si solar cells, light trapping becomes a crucial technology to enhance optical absorption in crystalline Si to achieve high energy conversion efficiency. We propose the use of CuInSe2 (CIS), an effective optical absorbed layer due to its direct bandgap of 1.03 eV, to grow epitaxially on the back of single-crystalline Si wafer and eliminate the light trapping design needed for conversional Si solar cells. This technique is even more powerful for its application on ultra-thin Si wafers (10~50 μm). In this work, we grew CIS epitaxial films on (100)Si wafers by three-source evaporation. XRD analysis indicated that the film grown epitaxially on Si, but the crystalline phase was identified to be Cu2In4Se7, a defect-ordered chalcopyrite compound. Auger depth profiling showed that the Cu:In ratios are 1:2 in the film and 1:3 at the surface for the film grown at 500oC and annealed in Se overpressure at 400oC for 30 minutes. Also, the Se content was significant lower than the expected value in the film but increased slightly near to the surface. The discrepancy of the film composition far from the stoichiometry of a chalcopyrite phase, i.e. Cu:In:Se=1:1:2, was attributed to the different evaporation rate of Cu2Se and In2Se3, which were formed prior to react to be a CIS compound. In addition, the Auger data revealed an amount of 5~10 at% Si in the film, which might be caused by the interdiffusion between the film and the substrate. Therefore, a low-temperature growth process, such as photo-assisted molecular beam epitaxy, should be employed for the CIS growth. On the other hand, extrinsic doping of Zn in CIS was investigated but not got a successful result. This suggests that an alternate candidate of group II element with less electronegativity, such as Cd, may be used to replace Zn as an effective n-type dopant. Finally, a PC1D simulation tool was applied to predict and optimize the device properties of a Si homojunction capped with a CIS bottom layer, i.e. n-Si/p-Si/p-CIS. We found that an increase in cell efficiency up to 28% for an ultra-thin (10 m) Si solar cell could be realized through the addition of a CIS layer with an optimized doping concentration.
    Advisory Committee
  • Mau-Phon Houng - chair
  • Tsung-Ming Tsai - co-chair
  • Bae-Heng Tseng - advisor
  • Files
  • etd-0805116-140206.pdf
  • Indicate in-campus at 2 year and off-campus access at 3 year.
    Date of Submission 2016-09-05

    [Back to Results | New Search]


    Browse | Search All Available ETDs

    If you have more questions or technical problems, please contact eThesys