The Chinese manufacturer said the result was confirmed by Tüv Rheinland. It was achieved by a sunken pyramid structure that reportedly reaches selective texture on the non-electrode area of the rear and a zebra-junction passivating contact structure that is said to guarantee excellent passivation.
Chinese polysilicium and solar -Module manufacturer Tongwei claims to have reached a 91.7% bifaciality factor in a 722 W solar module based on tunnel oxide passivated contact (topcon) solar cell technology.
“We have achieved this result with a top concel with a bifaciality of 94.3%,” the researcher of Tongwei, Xiajie Mix, told PV -Magazine. “It was certified by German certification body Tüv Rheinland. “
“We have already started a pilot who runs for a product with a bifaciality of more than 90%,” he said. “The mass production of panels with bifaciality of more than 85% will start this year. Reaching 95% cell bifaciality and 90% module Bifaciality in mass production is a major challenge, but we believe in the next one or two years that this will be possible.”
The company’s researchers explained that the result was made possible by two innovations in the cell design – one Selectively sunken pyramid structure and a zebra-curling passivation contact. As for the first, it helped to optimize the rear texture of the non-electrode area of the Celachterweg, while the second reportedly was able to improve the passivating of the N-Type passivating contacts based on polysilicium and Silicon monoxide (SIOX).
This cell configuration is claimed that it increases the harvest of environment labs and the energy yield of the module per W and at the same time extends the effective business hours.
For the cells, the scientists used 130 μm thick structured N-type Czochralski (CZ) silicon waffles cleaned with hydrochloric acid (HCL) and hydrofluoric acid (HF). They also used atomic layer deposits (ALD) to deposit a 4-NM thick aluminum oxide (AL2O3) layer on both cell sides for surface passion. The front was passivated with a 75-80 Nm thick Hydrogenated silicon nitride (Sinx: H) Low and the rear surface was treated with an 85-Nm thick sinx: H-film. They then carved (AG) electrodes and implemented slightly induced plattering.
The solar cell was tested under standard lighting conditions and appeared to be achieved an efficiency of the front of 25.67 %, an open circuit voltage of 742.15 mv, a short -circuit density of 41.30 mA/cm2 and a filling factor of 83.73 %, with the back act of 24.21 %.
“The rear-selectively structured cell shows a higher integrated short-circuit density of 41.29 mA/cm2 compared to 38.03 mA/cm2 for the polished back structure,” the researchers explained. “This improvement is attributed to the light of the rear texture, which improves light absorption. The structured area that fogs the poly-layer effectively reduces parasitic near infrared absorption losses.”
These cells were then used to build a 722 W-module that demonstrates a rear output of 662.1 W and a bifaciality factor of 91.7%. “These results not only emphasize the potential of topcon technology in environments with high reflectation, but also release the way for the sustainable design of powerful bifacial top-cone sun cells and modules,” the scientists concluded.
The new cell and module design was presented in the study “Which makes 95 % bifaciality of efficient topcon sun cells possible by selectively sunken pyramid structure and zebra-curling passivation contact contact“Published in Solar energy materials and solar cells. The research team included Academics of Chinese Southwest Petroleum University.
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