By combining heterojunction and back-contact technologies on a crystalline silicon solar cell with a practical size of 180cm^2, Japan’s Kaneka Corp. and New Energy and Industrial Technology Development Organization (NEDO) jointly improved the conversion efficiency to 26.33%, breaking the world’s efficiency record.
The previous world record of heterojunction back-contact type solar cell was 25.6%, while the new record set by NEDO and Kaneka demonstrated an efficiency improvement of approximately 0.7 percent as well as the world’s first crystalline silicon solar cell that has a conversion efficiency exceeding 26%. The efficiency record was achieved on a solar cell with a practical size that means an area of a 148~246cm^2, the conventional and mainstream size in the market.
“The levelized cost of electricity (LCOE) using photovoltaic technologies is still high compared with other power generation methods, and cost reduction is a continuous challenge. A number of companies and research organizations around the world have been carrying out technological development to improve the conversion efficiency of solar cells, which will contribute to a considerable reduction in LCOE,” noted NEDO.
The co-developing project “Development of High-Performance and Reliable PV Modules to Reduce LCOE” between NEDO and Kaneka has been targeting at reducing LCOE of PV power by improving solar cells’ conversion efficiency.
Heterojunction and back contact significantly increase efficiency
The “heterojunction” technology combines plural kinds of semiconductors with different properties to reduce defects which lower conversion efficiency or combining materials which convert the light energy of different wavelength ranges into electricity to obtain a higher conversion efficiency. It is most achievable to combine crystalline silicon and amorphous silicon (a-Si) materials together.
The back contact technology indicates to form an electrode pattern at the rear side of a solar cell to expand the front surface to receive light so that the efficiency can be enhanced. This structure changes conventional design of traditional PV cells that cover the front side of PV cells with electrode, which would reduce density of light gathering.
Kaneka combined its self-developed a-Si material with the heterojunction cells, and introduced technologies including low resistance electrode technology, and a back-contact structure that captures more solar energy, to achieve the 26.33% efficiency record.
Kaneka is planning to commercialize high-efficiency solar cells that utilize the results of NEDO's project and will move ahead with development for practical use. Furthermore, the partners will continue to develop solar cell technology for reducing cost and improving performance and reliability to achieve the target electric power generation costs of 14 yen/kWh in 2020 and 7 yen/kWh in 2030.
(source of graphics: NEDO)