Researchers in China have developed a strategy for fabricating large-scale, foldable silicon wafers for flexible solar cells.
A textured crystalline silicon wafer always starts to crack at the sharp channels between surface pyramids in the marginal region of the wafer. This enabled them to improve the flexibility of silicon wafers by blunting the pyramidal structure in the marginal regions.
Reducing the thickness of a 160-μm wafer to 60 μm provides flexibility similar to that of a sheet of paper, but this was not suitable for solar cell fabrication because more than 30% of the incident sunlight was reflected by its glossy surface. Chemically texturing microscale pyramids on c-Si surfaces has been widely used as an efficient strategy to reduce the reflectivity to less than 10%
The team at the Research Centre for New Energy Technology at the Shanghai Institute of Microsystem and Information Technology used the edge-blunting technique for commercial production of cells over 240 cm2 with over 24% silicon solar cells that can be rolled similarly to a sheet of paper. The cells retain 100% of their power conversion efficiency after 1,000 side-to-side bending cycles.
After being assembled into large (>10,000 cm2) flexible modules, the cells retain 99.62% of their power after thermal cycling between −70 °C and 85 °C for 120 h. They also retain 96.03% of their power after 20 min of exposure to air flow modelled on wind blowing during a violent storm.