It can bend more than 360 degrees, and Chinese scientists have developed a paper-like solar cell

The flexible monocrystalline silicon solar cell technology developed by Chinese scientists has been featured on the cover of the journal Nature.

According to the Shanghai Municipal Science and Technology Commission on May 25, the Shanghai Institute of Microsystem and Information Technology of the Chinese Academy of Sciences recently successfully developed flexible monocrystalline silicon solar cell technology. This technology can significantly improve the "flexibility" of silicon wafers, allowing flexible monocrystalline silicon solar cells with a thickness of 60 microns to be bent and folded like paper.

The findings were published in the May 24 issue of the journal Nature and were selected as the cover cover of the issue. The journal is one of the most prestigious scientific journals in the world.

Monocrystalline silicon solar cells were first invented by American researchers in the 50s of the last century and used in artificial satellites, when the photoelectric conversion rate was only about 5%.

After decades of development, monocrystalline silicon solar cells have become the mainstream technology adopted in the photovoltaic industry. At present, the photoelectric conversion rate of monocrystalline silicon solar cells has increased to 26.8%, close to the theoretical limit of 29.4%, and the market share in the photovoltaic market has also risen to more than 95%.

Photovoltaic conversion rate refers to the efficiency of solar cells in converting solar energy into electrical energy, which is one of the important indicators of solar cell performance. The higher the conversion rate, the better the performance of the solar cell.

At present, monocrystalline silicon solar cells are mainly used in distributed photovoltaic power stations and ground photovoltaic power stations, and there is still huge room for development in wearable electronics, vehicle mobile energy, construction and other fields.

Due to the brittle nature, bending stress and vibration may cause them to break, and monocrystalline silicon solar cells have limitations in some application scenarios.

The Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences (hereinafter referred to as the research team) found that when monocrystalline silicon breaks under bending stress, it always starts from the "V" shaped groove at the edge, indicating that this area is the "mechanical shortcoming" of monocrystalline silicon.

The above paper points out that by passivating the sharpness of the "V" shaped groove, the fracture behavior of monocrystalline silicon can be controlled, and its stress state and deformation mechanism under bending load can be changed.

Based on this, the research team has innovatively developed an edge rounding technology, which processes the sharp "V" shaped grooves on the edge surface and sides of the silicon wafer into smooth "U" shaped grooves.

The fracture pattern of the treated monocrystalline silicon has changed from "brittle" to "elastoplastic" secondary shear zone fracture behavior, which is less prone to fracture and can be folded and bent like paper at an angle of more than 360 degrees.

The above paper shows that this edge passivation technology can achieve commercial large-scale (>240 cm²) production of flexible monocrystalline silicon solar cells with a conversion efficiency of more than 24%.

Operational stability tests have found that these cells can maintain 100% power conversion efficiency after 1,000 lateral bending cycles. After 120 hours of thermal cycling (-70°C~85°C), the average relative power loss of a large (>10000 cm²) flexible module is only 0.32%.

In addition, when they are attached to a soft airbag and exposed to the air stream for 20 minutes, the power still retains 96.03%. The experiment mainly simulates the wind blowing during a storm.

According to the research team, because the sleek strategy is only implemented at the edge of the silicon wafer, it basically does not affect the photoelectric conversion efficiency of solar cells, and can significantly improve the flexibility of solar cells, and the cell technology has broad application prospects in space applications, green buildings, portable power supplies and other aspects in the future.

Previously, thin-film solar cells were flexible solar cells with high usage rates. This is a type of battery that is made using thin films. However, its photoelectric conversion efficiency is low, and its application is limited. Many companies engaged in thin-film solar cells at home and abroad have failed.

Solyndra of the United States uses cylindrical thin-film solar cells based on copper indium gallium selenide (CIGS) as its main products, but due to the high cost, low efficiency, fierce market competition and other reasons, it cannot compete with traditional crystalline silicon solar cells, and finally declared bankruptcy in 2011.

Q-CELLS, once a leading manufacturer of solar cells, also declared bankruptcy in 2012. Its subsidiary, Solibro, which specializes in thin-film solar cells based on copper indium gallium selenide, also filed for bankruptcy in 2019. Q-CELLS was later acquired by the Hanwha Group in South Korea and renamed Hanwha Q-CELLS.

Chinese company Hanergy Group, once one of the world's largest manufacturers of thin-film solar cells, alsoEventually, it went bankrupt。