An international research team in China has used n-type c-Si wafers from Czochralski of Sichuan Yongxiang, China to build textured wafers ranging in thickness from 65 μm to 55 μm. They have used wafers in heterojunction solar cells with a ton efficiency, which is close to the efficiency of cells in conventional wafer-based devices.
Researchers from the Chinese Academy of Sciences have successfully created bendable crystalline silicon (c-Si) wafers, known for their strong light-harvesting ability, for use in flexible silicon heterojunction (HJT) solar cells.
HJT cell technology is ideal for making flexible solar cells because it eliminates edge warping caused by internal stress during the firing process, the researchers said. The wafers are developed with a blunting treatment, which is commonly used to round the edges of the wafers to avoid chipping and cracking during processing. The researchers said the treatment led to a shift in the fracture mechanism from an intrinsic brittle crack to a shear band with steps and cracks.
The research team used 180 μm Czochralski n-type c-Si wafers supplied by China’s Sichuan Yongxiang to create textured wafers with a thickness of 60 μm.
The academics used the wafers to produce two HJT cells with thicknesses of 65 μm and 55 μm. The power conversion efficiency of the first cell was 23.31%, open circuit voltage 0.752 V, short circuit current density 0.09 mA cm−2, and a fill factor of 82.40%. The efficiency of the second cell was 23.35%, open circuit voltage 0.754 V, short circuit current density 0.11 mA cm−2and a fill factor of 82.51%.
The team then applied an anti-reflective coating based on magnesium fluoride (MgF2) to the cells, and their efficiency was increased to 24.50 percent.
“Although this value was lower than that of the thick cell (25.83%), due to the lower light-gathering ability of the thinner wafer, it was a remarkable efficiency compared to current flexible solar cells manufactured at other costs. -efficient materials,” the researchers said, noting that using a 60 μm wafer could reduce production costs by about 29%. “Overall, the flexible technology developed in this study reduced the levelized cost of energy by about 39% (23%) at the solar cell (module) level.
Academics presented a new fabrication process, “Flexible Solar Cells Based on Foldable Silicon Wafers with Blunt Edges,” published recently Nature. The research team includes researchers from China’s Tongwei (TW), Changsha University of Science and Technology, Southwest Petroleum University, Soochov University, and Beihang University.