Solar
energy is one of the most important green energies. The solar cell market grows
at an annual rate of 25%–30% and the learning curve yields a factor of two drop
in cost every 8–10 years, which makes it an attractive market. In spite of
the lower conversion efficiencies of the Si-based solar cells compared with the
compound semiconductor solar cells, they are the dominate mass production
technology, i.e., > 90%. The conversion efficiency decreases in the order of
sc-Si > poly-Si > μc-Si > a-Si. the thin-film approach is promising because it provides many
advantages, such as small amount of composing materials with unlimited
supplies at low costs, low-energy fabrication processes, and large-area
substrate capability. The thin-film poly-Si solar cell is promising for
commercial applications for its high conversion efficiency and stability.
However, the biggest challenge in thin-film poly-Si solar cell fabrication is
how to form the intrinsic and doped poly-Si thin films at a high rate under a
low thermal budget condition so that the large-size, low-cost substrate, such
as glass, used.
We have
successfully prepare the thin film poly-Si
film on glass used the pulsed rapid thermal
annealing (PRTA) method based on the vertical Ni-enhanced solid phase
crystallization mechanism. Individual intrinsic and doped a-Si thin films were
transformed into polycrystalline films. In addition, the a-Si pin stack has
also been transformed into the poly-Si stack.
Figure Programmed and actual temperature profiles of a 10-pulse PRTA
process.
35th
IEEE Photovoltaic Specialist Conference Proceeding, 2010.
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Figure Electron diffraction patterns of a PECVD a-Si nip stack (a) before and (b)
after a 10-pulse PRTA process.
35th
IEEE Photovoltaic Specialist Conference Proceeding, 2010.
Figure XRD of a PECVD intrinsic a-Si film
after dehydrogenation and a 10-pulse PRTA process (1s 850ºC-5s cooling ).
35th IEEE Photovoltaic Specialist
Conference Proceeding, 2010.
Mechanism of Crystallization
(a) (b)
Figure (a) NiSi2 formation at the early stage and (b) after
propagation through the complete nip stack.
35th IEEE Photovoltaic Specialist
Conference Proceeding, 2010.
Film Thickness Effect on Grain Structure
Figure 4. Raman spectra of poly-Si films formed from 30 nm and 100 nm thick
intrinsic a-Si films after 10-pulse PRTA process.
Zhu, Kuo, Lin, and Wang, 2011 MRS Proc. 1321, a-03-05 (2011)
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