Researchers from Purdue University, Florida State University, University of Kentucky, Lawrence Berkeley National Laboratory, University of Houston, Rice University, China's Qilu University of Technology (Shandong Academy of Sciences) and Taiwan's National Cheng Kung University have found that LEDs based on halide perovskites can produce more vivid, colorful and brighter images. The recent research presents extremely efficient perovskite LED devices in the red color region.
Perovskite materials often tend to be less stable and can degrade quickly. Further, device efficiency has not been fully optimized to compete with conventional LEDs. “Our work aims to resolve these critical issues,” said Purdue's Letian Dou, who conceived the idea, supervised the project and provided funding support.
Dou’s postdoctoral researcher, Kang Wang, was instrumental in the process. He synthesized the organic ligands and incorporated them into the hybrid perovskite thin films to improve the phase purity, reduce defect density and improve stability. Then, he clarified the effect of ligands on the crystallization mechanism of the perovskite films by combining a series of in-situ and ex-situ characterizations. Finally, he fabricated very efficient LED devices based on the optimal ligand and film and conducted data analysis.
“We achieved efficient and stable deep-red LEDs with a peak external quantum efficiency of 26.3%, which is the highest efficiency for red perovskite LEDs. The stability results are also better than the perovskite LEDs based on similar materials,” Wang said. “In addition, our devices exhibited wide wavelength tunability and improved spectral and phase stability compared with existing perovskite LEDs.”
Fundamentally, these discoveries provide critical insights into the molecular design and crystallization kinetics of low-dimensional perovskite semiconductors, which is critical for light-emitting devices.
“Realistically, the molecular engineering strategy shown in this work could be expanded to other perovskite-based optoelectronic devices, and it also suggests that there is a bright future in transforming perovskite LED technology into real-world applications,” Dou said.
“We will keep pushing the efficiency and stability of LEDs to a commercialization level — for example, an external quantum efficiency of 30% and half-life of 10,000 hours,” Dou said. “These are the basic requirements for LED devices in practical use. We are very optimistic about soon achieving this goal by combining our rationally designed organic ligands with halide perovskite semiconductors. We will soon extend our strategy to make efficient green and blue LEDs to realize full-color displays. We have obtained some preliminary results, which makes me feel we are on track.”