Researchers at Linköping University, working with colleagues in Great Britain, China, and the Czech Republic, have developed a perovskite LED with both high efficiency and long operational stability. The result has been published in Nature Communications.
“Light-emitting diodes based on perovskites are still not sufficiently stable for practical use, but we have brought them one step closer,” said Feng Gao, head of research at the Division of Biomolecular and Organic Electronics at Linköping University.
The special crystal structure of perovskites means that they have desirable optical and electronic properties while still being easy and cheap to manufacture.
“Much remains to be done,” said Xiao-Ke Liu, a co-author of the article and a research fellow in the Division of Biomolecular and Organic Electronics. “Until now, most of the perovskite LEDs have either low efficiency or poor device stability.”
The researchers at Linköping used a perovskite that consisted of lead, iodine, and an organic substance, formamidinium. They then embedded the perovskite into an organic molecule matrix to form a composite thin film. The new composite thin film has enabled the research group to develop LEDs with an efficiency of 17.3% with a long half-lifetime, approximately 100 hours.
“This molecule with two amino groups at its ends helps the other substances to form a high-quality crystal structure that is characteristic for perovskites, and makes the crystal stable,” said Heyong Wang, a doctoral student in the Division of Biomolecular and Organic Electronics.
“We would very much like to get rid of the lead. So far we haven’t found a good way to do this, but we are working hard on it,” Gao said.
The researchers said their next steps are to test new combinations of different perovskites and organic molecules and to understand in detail how the nucleation and crystallization processes occur. Different perovskites give light at different wavelengths, which is a requirement for the long-term goal of obtaining white-light LEDs.