Tin-based perovskite LED efficiency increased to 8.3%

The research team of Wang Jianpu, a professor at the School of Flexible Electronics (Future Technology) of Nanjing University of Technology, has made a major breakthrough in environmentally friendly perovskite light-emitting diodes. The external quantum efficiency of the tin-based perovskite light-emitting diode device constructed by the team based on scientific methods reaches 8.3%, which is the highest efficiency of tin-based perovskite light-emitting diode at present, and provides a new idea and approach to achieve higher performance tin-based perovskite photoelectric devices. A few days ago, the relevant research results were published in Nature Photonics.

In situ fluorescence spectra of tin-based perovskite films with no additives during spin coating, as well as schematic diagram of crystal growth. Photo courtesy of the research group

Metal halide perovskite materials have excellent photoelectric properties and solution-ready processing characteristics, and show broad application prospects in solar cells, light-emitting diodes, photodetectors and other fields. However, high-efficiency perovskite light-emitting diodes are still dominated by lead-based perovskites that are not environmentally friendly, which will limit their practical application.

Wang Nana, a professor at the School of Flexible Electronics (Future Technology) of Southern University of Technology, said that in recent years, the team has successively increased the external quantum efficiency of tin-based perovskite light-emitting diodes to 3% and 5.3%, but the device performance is still much lower than that of lead-based devices, mainly due to the rapid crystallization speed of tin-based perovskites, resulting in the formation of more film defect states, and the defect state is often the luminescence quenching center, making it difficult to improve the luminous efficiency of the device.

In order to solve this world problem, the team found that the rapid aggregation of grains in the early stage of tin perovskite film growth (within 10 seconds) is the main cause of defect state formation through in situ spectroscopic characterization. They abandoned the original idea of “perfecting the film while making”, and directly “intervened” at the source, that is, at the beginning of the growth of tin-based perovskite films.

“If the tin-based perovskite film is compared to a pancake, then the original anti-solvent assisted crystallization method is like adding force to an unevenly spread ‘pancake’ to make the ‘pancake’ smoother; the solvent atmosphere control crystallization method is to control the environment to make the ‘pancake’ more uniform.” Chang Jin, associate professor of Nanjing University of Technology, said that they tried to introduce a class of additives (represented by vitamin B1) with strong chemical effects on components such as stannous iodide in the perovskite precursor solution, effectively inhibiting the rapid aggregation of perovskite grains, reducing the formation of luminescent quenching centers during the growth of perovskite crystals, and making the grains “aggregate” in a more orderly manner. Based on this method, the external quantum efficiency of tin-based perovskite light-emitting diode devices reaches 8.3%.

It is reported that the first authors of the paper are Min Hao, a graduate student of Nanjing University of Technology, and Chang Jin, associate professor, and Wang Jianpu, academicians of the Chinese Academy of Sciences, Huang Wei and Wang Nana, are the corresponding authors of the paper. The first author of the paper is Nanjing University of Technology. (Source: China Science News, Wen Caifei, Zhu Lin)

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