清华大学材料科学与工程研究院《材料科学论坛》
摘要：
The efficiency of Cu(InGa)Se2 (CIGS) solar cells was higher than 20%, even though the CIGS absorber layer is polycrystalline and the solar cell is a hetero-junction solar cell. Thus the understanding of grain and grain
boundary (GB) properties is quite important for further improvement of their efficiencies. We have comprehensively characterized the CIGS films by electron beam probe analysis and scanning probe microscope-based
investigation.
The CIGS absorber layer was fabricated by a three-stage method. The solar cell structure was SLG/Mo/CIGS/CdS/ZnO, and the Ga composition was about 20%. The solar cell efficiencies were ranging from 15% to 16%.
It was observed from the cross-sectional and surface electron beam induced current (EBIC) mappings that the EBIC signals at GBs were brighter than the grains, suggesting the conduction band minimum at GBs has a convex structure. Furthermore, the scanning spread resistance measurement (SSRM) showed that the resistivity of GBs was lower than the grain. The result also implies the valence band maximum has a convex structure, resulting in the accumulation of holes (majority carrier). The band structure at the GB is suitable for the solar cell application, because the electron-hole pair produced at GBs easily separates due to the internal electric field and the electron (minority carrier) is repelled from GBs, resulting in the higher minority carrier correction and in the suppression of carrier recombination at GBs.
Furthermore, we observed grain-by-grain difference in the intensity of EBIC signals. The cross-sectional transmission electron microcopy (TEM) showed that the stacking faults were observed in the grains with darker EBIC signal and that the crystal structure of CdS layer touched with the stacking faults was deteriorated, suggesting a possible leakage path in the solar cell. These facts are quite important to deduce how to improve the solar cell efficiencies.
Curriculum Vitae
Name: Akira YAMADA
Place and Date of Birth: Yamanashi Prefecture, Japan, April 3, 196
Age: 48
Education:
Bachelor of Engineering, Department of Physical Electronics,
Tokyo Institute of Technology (1984)
Master of Engineering, Department of Physical Electronics,
Tokyo Institute of Technology (1986)
Doctor of Engineering, Department of Physical Electronics,
Tokyo Institute of Technology (1989)
Employment:
Research Associate, Tokyo Institute of Technology (1989)
Lecturer, Tokyo Institute of Technology (1990)
Associate Professor, Tokyo Institute of Technology (1994)
Visiting Researcher, Paul-Drude Institute (1995, Germany, 1 year)
Professor, Tokyo Institute of Technology (2008)
Present:
Professor
Department of Physical Electronics, Tokyo Institute of Technology
Major research fields:
1989~ Low-Temperature Si Epitaxy by Photo-Chemical Vapor Deposition
1991~ Development of High-Efficiency Amorphous Silicon Solar Cells
1991~ Development of High-Efficiency Cu(InGa)Se2 Thin-Film Solar Cells
2000~ Development of MOSFET with a Strained-Si Channel
Awards:
PVSEC Paper Award (PVSEC-12, 2001)
WCPEC Poster Award (WCPEC-3, 2003)
JJAP Editorial Contribution Award (JJAP, 2003)
Best Paper Award (PVSEC-15, 2005)
Award for Best Oral Presentation (PVSEC-18, 2009)
Poster Award (24th EU-PVSEC, 2009)
Best Paper Award (PVSEC-19, 2009)
联系人：林 红 老师 62772672 |
