A group of scientists has developed highly-elastic silicon solar cells that fold like paper. The thin and flexible solar-powered material can be used in areas ranging from aerospace to electronic wearables, according to the Chinese-based research team.
Silicon photovoltaic (PV) cells account for an estimated 95 per cent of the market and have been used in the industry since grid-connected solar arrays rose to popularity in the 1990s.
Since then, the manufacturing costs of cells have steadily decreased, while energy-generating efficiency has increased, nearly reaching the theoretical light-electricity conversion rate of 29.4 per cent in ideal conditions.
However, creating a flexible solar cell that is efficient but inexpensive enough to be commercially viable has puzzled scientists.
While the thin-film solar cells currently used in the PV industry are elastic, they are somewhat inefficient and filled with potentially lethal compounds, says Liu Wenzhou, lead scientist and professor at the Shanghai Institute of Microsystem and Information Technology (SIMIT).
Compounds such as lead-containing perovskite and cadmium telluride, a cytotoxic agent that can cause tissue death, pulmonary inflammation and fibrosis in mammals.
This combination of inferior performance and the potential for the harmful contents to contaminate the local environment has meant thin-film solar cells have seen limited use at any meaningful scale, said Liu.
To overcome this, Liu, his fellow SIMIT researchers and representatives for the Saudi Arabian Oil Company, began by using high-speed cameras to observe how silicon solar panels react when subjected to bending stress.
They found a pronounced weak point in nearly all test subjects: the V-shaped groove at the very edge of each silicon wafer. So the team, whose work was published in the peer-reviewed scientific journal, Nature, replaced the V-shaped grooves with smoother U-shaped grooves.
The result was that the adjustment better distributed the bending strain on the subjects and suppressed the wafer’s propensity to snap. The study’s co-author, Di Zengfeng, described the end product as lightweight and flexible, without sacrificing its efficiency.
The experimental solar cells have unmatched flexibility, according to the team’s peer-reviewed study, with a 60-micrometre-long, thin-film cell bending and folding like a sheet of printing paper.
Liu and his colleagues described the silicon cell as capable of measuring a bend radius of 5 millimetres and can achieve a bend angle of more than 360 degrees. It is also resilient enough to withstand repeated bending and manipulation. Durability testing revealed the cells retained 100 per cent of their energy conversion efficiency after 1 000 “side-to-side” bending cycles.
Each test subject was exposed to temperatures ranging between -70 degrees Celsius and 85 degrees Celsius for up to 120 hours, recording an average post-test efficiency of 99.62 per cent.
The researchers simulated violent weather conditions, battering the cells with 30 metre-per-second wind gusts from a powerful fan, finding that after 20-second continuous air impacts, each unit only lost roughly 3 per cent of its power generation potential.
Despite their work only recently being published, the novel thin-film silicon cells have already seen use in the field. According to the team’s report and an article published by South China Morning Post, the energy-generating material has been integrated with near-space vehicles, buildings and even motor vehicles.
While delighted with the team’s progress, Liu called for more testing, stating it would guarantee a more reliable and consistent performance during real-world applications.