On December 29, 2017, at the Key Laboratory of Green Printing of the Chinese Academy of Sciences, researchers showed the reporters of China Science Daily their newly prepared perovskite flexible solar cells with similar thickness and pliability to those of a magazine paper Over the past three years, they have used 'typography' to break through the challenges of flexible perovskite solar cells and are expected to provide reliable power to flexible wearable electronic devices, a recent achievement in the international academic journal Adv. Mater. On the issue.
Newly developed perovskite flexible solar cells drive the fan to rotate (Photo courtesy of the Chinese Academy of Sciences)
This study prepared perovskite honeycomb nanostructures by nanocomposite-printing and built 'optical resonators' within them, both innovations improving both the mechanical stability of the flexible perovskite solar cells and the photoelectric Conversion rate.
New application of perovskite materials
'If the smart watch can be equipped with solar power strap, do not have to charge every day.' Speaking of the original intention of carrying out the study, the first author of the paper, Chinese Academy of Sciences, PhD student Hu Xia Tim said. Perovskite efficiency of exponential growth And inkjet printing technology accumulation of perovskite single crystal material let him see the possibility that this idea realizes.
Perovskite photoelectric conversion efficiency, low price, is a good solar cell material.While a lot of laboratories are how to make perovskites instead of silicon batteries work hard, Song Yanlin team saw another application direction - Flexible solar power generation materials.
Researchers on the perovskite 'love and hate', its thin, the thickness of the substrate within a millimeter, very likely to wear on the body may be; but the material is brittle, intolerant to bending .In order to increase the bending nature, Attempts to wrap the perovskite up and down with soft materials have failed to deliver the results, and ultimately he was inspired by the most stable mechanics of the natural bee hive to produce 'honeycomb-like nano-assemblies Bracket 'can be used as a mechanical buffer layer to achieve a higher mechanical stability of flexible perovskite solar cells.
At the same time, the photoelectric conversion rate of perovskite battery is also one of the problems to be solved.As a result of technical limitations, the larger the area of perovskite thin film, the lower the photoelectric conversion rate.Hu Xia Tim put in the optical resonator within the device to achieve A photoelectric conversion of 12.32% over a 50 cm2 area achieved a major breakthrough in large area repeatability of high efficiency cells.
Printing preparation to provide technical accumulation
In fact, Song Yanlin group to overcome the nature of perovskite breakthrough can not be separated from their accumulation in the green printing technology.Different from the traditional graphic materials printed content, Song Yanlin group proposed the concept of 'big printing', you can put Various functional materials are printed onto the substrate by means of printing.Nowadays, researchers' 'printing skills' have been accurate to the nanometer scale and can print' the finest lines' and 'the smallest dots.' Last year, experiments The room has also made wearable sensors that recognize complex facial expressions and are expected to be used in areas such as pulse monitoring, heart monitoring and remote control.
Perovskite cell preparation is through the inkjet printing of perovskite monocrystalline material printed on the substrate. "Song Yanlin said.
Not only that, honeycomb-shaped nanostructures for improving bendability are also prepared by printing: 'We use ink-jet printing to assemble honeycomb-sized balls into a single-layer closely packed form, and then fill the gap between the ball and the ball In the middle, the ball is washed away to form a honeycomb net.
Large area of flexible materials can be expected in the future
Three years, more than 2000 devices, Song Yanlin led the group in this research attempt. 'Seasonal changes in humidity have a great impact on the success rate of the experiment, as with the luck, every step is very careful, But in the end the performance of the device is not good. "Song Yanlin memories. In the three years of project research, Hu Xia Tim and task force members do at least three samples out of the test value every day.
Hu Xiao Tim tweezers used to pick up a fingernail-sized glass, a dark brown perovskite solar cells inlaid them.
'This is currently the research direction of most laboratories to achieve a large photoelectric conversion rate in a very small area, this material conversion rate of about 20%, but the area is too small, generating only a few milliwatts, the application The value is not enough. 'Song Yanlin said that scientific research should be applied to the application of perovskite solar cells can not blindly pursue the high conversion rate while ignoring the availability of At present, the laboratory focus on large areas and flexible, larger area, easier Folded perovskite battery research is expected to be released next year.
In spite of the many problems that go beyond the perovskite solar cell lab, researchers are still optimistic about its future applications.In addition to wearable devices, the future, perovskite batteries may also be used in clothing, automotive glass film and other places to absorb sunlight, Converted power to other devices, both environmentally friendly and practical.