Flexible CIGS photovoltaic cell hits energy conversion efficiency of 17.7%

Shigeru Niki and Shogo Ishizuka of the National Institute of Advanced Industrial Science and Technology (AIST), with cooperation of Teijin Limited, have developed a technique for dramatically improving the energy conversion efficiency of flexible photovoltaic cells that use CIGS, a non-silicon material. The technique is used to fabricate high-performance photovoltaic cells with a variety of flexible substrates such as ceramics, metal foils, and polymers.

The CIGS photovoltaic cell has many excellent features including such high energy conversion efficiency and long-term reliability with no aged deterioration. CIGS photovoltaic cells are already produced commercially and sale of solar panel modules have been started in 2007 by Japanese manufacturers.

The thickness of the photoelectric conversion layer in solar cells that use CIGS, a semiconducting material made of copper (Cu), indium (In), gallium (Ga), and selenium (Se), can be reduced to the order of several micrometers. Owing to this feature, light-weight and flexible photovoltaic cells that can be installed on a curved surface and portable photovoltaic cells are expected to be realized.

One of the technical issues remaining to be solved for improvement of the performance of flexible CIGS photovoltaic cells is the control of the alkali doping level in the CIGS absorber layer.

The AIST researchers used alkali-silicate glass thin layers (ASTL) as alkali source materials, which are stable alkali compounds, deposited on the substrate prior to the molybdenum (Mo) back contact layer deposition and developed a technique for controlling the quantity of alkali incorporated into the CIGS absorber layer through the Mo back contact layer by controlling the deposition conditions of ASTL (the “ASTL method”). This technique allows easy alkali addition and high reproducibility, and thus, can bring about a significant improvement in the energy conversion efficiency of CIGS photovoltaic cells. The team fabricated a small-area flexible CIGS photovoltaic cell with a ceramics substrate with smooth surface using the ASTL method and achieved an active-area efficiency of 17.7%. This is the highest value for flexible CIGS cells reported to date.

The results of this research will be announced at the 23rd European Photovoltaic Solar Energy Conference and Exhibition to be held in Valencia, Spain on September 1-5, 2008.

The research was supported by the Research and Development of Future Photovoltaic System Technologies
project of NEDO.

Source and more info: http://nanonet.mext.go.jp/modules/basenews/article.php?a_id=375


~ by vascoteixeira on August 25, 2008.

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